Introduction

Intercellular Communication and DNA Messaging

Intercellular communication between cells in nature allows for coordinated population-level behavior, enabling spatial and temporal organization and complex responses to environmental stimuli. Synthetic biology is continually expanding the range of programmable cellular characteristics and behaviors, and incorporation of intercellular communication into engineered cell populations has extended programmable behavior to a population level.

Engineered AHL-based intercellular communication

Many bacteria naturally secrete acylated homoserine lactone molecules, or AHLs, which can be detected by other members of the bacterial population. Concentration-sensitive detection of AHL brings about significant qualitative changes in cell behavior via transcription regulation, including feedback on AHL production. Such natural quorum sensing systems are associated with coordinated behaviours such as biofilm formation [1] and bioluminescence [2]. These natural bacterial quorum-sensing systems have been successfully modulated to enable programmed intercellular communication in engineered bacterial populations. In this approach, genes associated with AHL production, detection, and response are “re-wired” such that they correspond to different input stimuli and output behaviors. Coordinated population-level behaviors including two-dimensional pattern formation [3], coordinated oscillations in gene expression [4], and even a system exhibiting predator-prey dynamics [5] have been demonstrated using this technique.

Why DNA messaging?

While AHL-based communication is a useful approach for engineering population-level coordination of bacterial cells, the quorum sensing messaging system has some inherent weaknesses that limit the diversity and information content of messages that can be communicated using this method. Ortiz and Endy [6] note that AHL communication acts only through regulation of transcription. In this way, the diversity of messages in AHL-based communication is restricted to regulation of genes present in the receiver. They also note that the receptor or transcription factor affected by a particular AHL can only respond in one way, or perhaps a few ways if different concentrations correspond to different responses; that is, a single type of AHL signaling molecule cannot be used to communicate a great number of different messages within the same communication system. In order to diversify the number of potential messages, additional types AHL molecules must be used. In this way, the message and the molecule are coupled: “the message is the molecule”.

To improve in these areas, Ortiz and Endy designed and demonstrated a communication system where DNA is used as the messaging molecule used for information exchange between cells [6]. These “DNA messages” are carried between cells inside a hijacked M13 bacteriophage particle: through a cunning act of trickery, M13 viral proteins are deceived into packaging the non-viral DNA message inside viral particles instead of the viral genome itself. (Keep reading for details).

Baseballs and Bottles

An analogy is useful in appreciating the expansion of potential for communication afforded by DNA messaging over AHL based messaging. Consider the following absurd but illustrative situation:

Suppose you and I both natively speak, read, and write Italian, and I would like to communicate with you about how I am feeling. Suppose also that we are unfortunately too far away to speak directly and it is too foggy for us to see each other (no gestures), so we are forced to communicate by hurling baseballs over to each other. When I hurl lots of baseballs to you, you know I am in a particular mood, and when I hurl fewer you know I am in a different mood. Perhaps if I got very fancy I could devise a few patterns in my hurling that would add even one or two more expressible feelings to my repertoire. Or maybe if I had some tennis balls or golf balls I could hurl those as well, extending my expression a little further. While I would be profoundly grateful for this crude outlet for sharing my feelings through hurling baseballs, I would long to explain to you, in words, all the colorful flutterings of my heart.

Imagine, now, a slight change in the situation. Imagine that I have a pile of (unsmashable) bottles, a notepad, and a pen. Now instead of hurling baseballs, I can hurl bottles to you. But inside these bottles I can put a note, written in Italian! Provided we can write and read Italian, which we both can, I can send you an arbitrary range of messages expounding my full range of thought and emotion. I can philosophize, make jokes, and write you love letters, all in our native language of Italian.

The difference between these two scenarios is in the fundamental nature of our messaging tools. The problem with the first scenario is that baseballs, tennis balls, and golf balls are not able to carry much information! We can get some use out of them by setting up a system where you are able to detect how many balls I am throwing, but this could never compare to communication in our shared native language of Italian. Notepads and pens are tools that were specifically designed for communication in Italian, which allows for transmission of rich and densely encoded information.

As you’ve likely picked up, AHL here is analogous to baseballs, and DNA is analogous to a written note in Italian. An M13 viral particle is the bottle carrying the note. While AHL can be used by cells to communicate, it is not a particularly good information-encoding molecule. DNA is the master information molecule – it was specifically designed for this by nature – and all cells read and write the language of DNA. It is for this reason that DNA holds so much promise as an intercellular messaging molecule!

The Nuts and Bolts of DNA Messaging

Several key aspects of the M13 filamentous bacteriophage were harnessed by Ortiz and Endy [6] in their original design of the DNA messaging system. Tricking M13 proteins into packaging heterologous DNA: In nature, M13 viral proteins package the M13 genome into viral particles. The M13 DNA is recognized through the M13 packaging sequence. Any DNA containing this packaging sequence will be packaged into viral particles. By removing the M13 packaging sequence from the M13 genome and placing it on a plasmid, we can trick the viral proteins produced from the M13 genome into packaging the plasmid DNA instead of the M13 DNA. A plasmid carrying the packaging sequence is called a phagemid, and a version of the M13 genome that does not efficiently package itself due to a reduced or removed packaging sequence is called a helper plasmid. A phagemid will be packaged into a viral particle in the presence of a helper plasmid. DNA of arbitrary length can be packaged: M13 viral packaging occurs at the cell membrane, where the viral particle forms around the DNA as it is packaged and slowly secreted, forming a long filament. This allows DNA of arbitrary length to be packaged [7]. M13 is not lytic: Since M13 viral particles are secreted through the cell membrane, infected cells are able to continue living and dividing, albeit at ½ to ¾ their normal rate [7]. Because of this, cells sending a DNA message need not commit suicide to transmit their message!

Only F+ cells can be infected: The M13 bacteriophage must attach to the F pilus of an E. coli cell in order to infect it. Therefore, only E. coli cells carrying the F plasmid (F+ cells) are susceptible, while F- cells are not. Sender cells contain a messaging phagemid and a helper plasmid, which allows them to secrete viral particles. Receiver cells must be F+. When the two cell populations are co-cultured, DNA messaging will take place. (Fig 1)

Fig 1 A sender population carrying a messaging phagemid and a helper plasmid can transmit a DNA message to an F+ receiver plasmid in co-culture.

DNA messaging was first established in 2012 when Ortiz and Endy demonstrated transmission and receipt of a DNA message encoding GFP and ampicillin resistance, as well as a separate message encoding T7 RNA polymerase [6]. This proof of principle demonstration indicates the viability of DNA messaging and suggests extension of the method to diversify potential communication programs.

The Idea: Controlled Modification and Transmission of a DNA Message

We have identified three extensions to DNA messaging that would diversify potential intercellular messaging programs.

• DNA messages should be modifiable using well-established methods of site-specific recombination, allowing incorporation of digital DNA logic and memory into messaging programs.

• Transmission of a DNA message should be controllable. It would be useful to be able to send DNA messages only at certain times, in response to a particular stimulus.

• Receiver cells should be able to modify and re-transmit a DNA message, lengthening the potential “conversation” between cells.

Controlled Modification of a DNA Message

Diversity in the interactiveness of DNA messages with sender and receiver cells could be improved by incorporating established methods of site-specific recombination into DNA messaging. This would allow sender and receiver cells to change the message in controlled ways. Recent work with serine integrase site-specific recombinases has demonstrated their utility in implementing digital memory [8] and Boolean logic [9,10] in DNA through inversion of DNA sequences (See the Serine Integrases page). We sought to incorporate an invertible promoter switch on a messaging phagemid that can be flipped using a serine integrase. This switch could be flipped inside sender cells before transmission of the message, or in receiver cells after transmission of the message. As part of this goal, we produced four invertible promoter switches. These switches consist of a promoter sequence that can be inverted using a serine integrase, flipping the orientation of the promoter on the DNA strand. Since the promoter changes orientation when the switch is flipped, different genes are expressed depending on the state of the switch. These switches were directly inspired by the recombinase addressable data (RAD) module developed by Bonnet et al [8], which was closely mimicked in our design. We produced two switches controlled by Bxb1 integrase, and two switches controlled by PhiC31 integrase. Incorporation of a switch like these on a messaging phagemid would allow the message to take on two different forms depending on the state of the switch, potentially corresponding to vastly different responses in the receiver population. See the design page and lab page for details on our work toward this goal.

Controlled Transmission of a DNA Message

The utility of DNA messaging could be improved by controlling when messages are sent, so that DNA messages could be sent in response to a particular stimulus. This requires that packaging of message DNA into M13 bacteriophage particles be controlled. Control over viral particle production was previously accomplished in bacteriophage ϕX174. The gene encoding the ϕX174 major coat protein was removed from the viral genome and placed under an inducible promoter on a plasmid, and induction of this gene was successfully used to control production of ϕX174 viral particles [11]. To obtain control over viral particle production, we sought to control expression of M13 g8, which codes for the M13 major coat protein p8. We expected that induction of M13 viral particle production would be possible through inducing expression of g8 in the presence of all other M13 genes. See the M13 bacteriophage page for more details on M13 bacteriophage. See the design page and lab page for details on our work toward this goal.

Controlled Modification and Retransmission of a DNA Message by Receiver Cells

By combining control over DNA message transmission and modification, we sought to demonstrate controlled modification of a DNA message in receiver cells followed by retransmission of the modified message. Modification and retransmission should occur only in the presence of a particular stimulus. This would extend the utility of DNA messaging by allowing receiver cells to respond to messages by sending out more messages, enabling a sort of conversation between cell populations. See the design page for more details.

Serine Integrase

The design for accomplishing our goals uses the site-specific recombinase activity of serine integrase enzymes found naturally in various bacteriophages. In nature, serine integrases (Int) allow phages to integrate into the bacterial genome through site-specific recombination between attachment sites on the phage and bacterial genomes (attP and attB), both of which are between 30 and 60 bp depending which phage serine integrase is considered. Recombination between attP and attB leaves behind left and right attachment sites (attL and attR) (Fig 1), which cannot be acted upon by Int alone. Thus, in the presence of Int alone, this recombination is irreversible [12]. In order for the phage genome to excise from the bacterial genome, recombination between attL and attR sites must occur; this reproduces the original phage and bacterial genomes. To this end, phages that exploit serine integrases also have a “recombination directionality factor” (RDF) which reverses the recombination activity of Int; that is, coexpression of Int and RDF allows recombination between attL and attR sites to reproduce attP and attB sites, and inhibits recombination of attP and attB (Fig.2) [12].

Figure 2. Recombination between attP and attB leaves behind attL and attR sites and allows for integration of the phage genome into the bacterial genome in nature. RDF reverses this activity. Adapted from Groth and Calos, 2004 [12].

By placing attP and attB sites in the correct orientation on the same DNA sequence, the DNA segment between them can be inverted through integrase activity. By placing a promoter on the segment between the att sites and placing a promoterless gene or operon on either side of the invertible sequence, a switch is produced that will lead to transcription of different genes depending on its state. Note that such a switch is flipped from “PB state” (attP and attB sites) to “LR state” (attL and attR sites) by integrase alone, while it is flipped from LR state to PB state by integrase in concert with RDF [13]. An example of such a switch, with GFP or RFP being produced depending on its state, is shown in the Video.

This DNA inversion technique has been used to implement passive digital memory in live cells. More recently, this technique has been extended to the implementation of two-input one-output Boolean logic gates [14,15]. In our project, we use integrase/RDF pairs from bacteriophages Bxb1 and PhiC31. We have constructed four invertible promoter switches, which are designed based on the recombinase addressable data (RAD) module developed by Bonnet et al. [13] and can be flipped using these integrases.

M13 Bacteriophage

Under Construction

Design

Controlled Modification of a DNA message

One advantage to DNA messaging is that well-established methods of DNA recombination could potentially be incorporated into intercellular communication programs. We sought to demonstrate this by placing an invertible promoter switch (described below) on a DNA message, which can be flipped using a serine integrase. By placing an invertible promoter switch on a DNA message, we make the message modifiable. The message could be modified in sender cells or receiver cells through production of the serine integrase corresponding to the switch.

Invertible Promoter Switches

Recent work with serine integrases has demonstrated their utility in implementing digital memory and Boolean logic in DNA through inversion of DNA sequences (see page on Serine Integrases). We sought to incorporate an invertible promoter switch into a DNA message, consisting of a promoter whose orientation can be flipped through action of a serine integrase and a corresponding recombination directionality factor (RDF). This would allow the message to take on two different forms depending on the state of the switch. These two forms could correspond to vastly different responses in the receiver population.As part of this goal, we designed four invertible promoter switches (Fig 1). Two switches correspond to the Bxb1 integrase/RDF system, and two correspond to the PhiC31 integrase/RDF system. Our design is directly inspired by and closely mimics the recombinase addressable data (RAD) module designed by Bonnet et al [16]. The invertible promoter switch in the RAD module consists of a promoter flanked by Bxb1 att sites, with a transcription terminator upstream of the promoter. The terminator guards against transcription of genes upstream of the promoter that should only be transcribed when the switch is in its opposite state. See the lab page for information on our implementation of invertible promoter switches and the integrase/RDF BioBricks we produced for working with the switches.

The “PB” state of the switch is the one in which the promoter is flanked by attP and attB sites, while the promoter is flanked by attR and attL sites in the “RL” state. Flipping from PB to RL is catalyzed by integrase and is irreversible in the presence of integrase alone. Flipping from RL to PB is catalyzed by integrase in conjunction with RDF, and is irreversible in the presence of these enzymes together. For more on the functioning of integrase and RDF in site-specific recombination of att sites, see the Serine Integrases page. Since the switch in the RAD module was demonstrated to be functional, we replicated its architecture exactly in our switches. Intervening spacer sequences between functional elements are also the same in our switches.

Our four switches are portrayed here in PB state (Fig 3).

Fig 3. Schematic diagram of our invertible promoter switches. The orientation of the promoter can be flipped using the integrase corresponding to the att sites in the switch.

Genes placed on either side of the invertible promoter switch will be expressed when the switch is in a state such that the promoter drives their expression. Genes added to the prefix side of the switch will be expressed in PB state, and genes added to the suffix side will be expressed in RL state. Flipping from the PB to RL state and back through action of integrase and RDF is illustrated in figure 4.

Figure 4. The state of an invertible promoter switch can be flipped through the action of integrase and a recombination directionality factor (RDF). Since the promoter is in a different orientation in each state, a different set of genes is expressed depending on the state of the switch.

It is important to note that any genes added to the prefix side of the switch must be inverted relative to the BioBrick convention, i.e. they are transcribed from suffix to prefix, rather than prefix to suffix. These inverted genes are expressed when the switch is in PB state. These switches may be used as a form of passive memory storage. This memory storage is described as passive because it holds its state after the stimulus (Int or Int+RDF) has passed. It does not require active gene expression to hold state, in contrast to switches that function through regulation of transcription (eg a mutual inhibition toggle switch [17]). It should also be noted that in our BioBrick switch constructs there is an NheI restriction site outside of the functional switch portion of the BioBrick close to the prefix. This NheI site is an artifact of a design idea we had early in our project’s design phase and does not have a functional role. It is not expected to affect the functioning of the switch.

Controlled Transmission of a DNA Message

Setting out to design a system that regulates DNA messaging by controlling M13 particle production, we had the option of manipulating any of the 11 genes in the M13 genome (see the M13 Bacteriophage page). In our design, viral particle production is regulated by controlling production of M13 protein VIII. The protein product of M13 gene VIII, protein VIII, is the major coat protein of the M13 phage; wild-type viral particles contain ~2700 copies [18], though this will vary based on the length of the DNA being packaged. The choice to control gene VIII was made based on several factors:

A similar goal was previously accomplished in bacteriophage ϕX174 using the same approach. The gene encoding the ϕX174 major coat protein was removed from the viral genome and placed under an inducible promoter on a plasmid, and induction of this gene was successfully used to control production of ϕX174 viral particles [19].

Gene VIII is an important structural component of the phage particle, but it is not known to have any regulatory function in the M13 genome. Any genes involved in regulation might be more difficult to manipulate while preserving the function of the system.

Gene VIII is the last gene in an operon on the M13 genome. Removing it from the genome is therefore less likely to affect the expression or regulation of other genes.

To control gene VIII expression, we sought to remove gene VIII from the helper plasmid and place it on the messaging phagemid under the control of an inducible promoter. When gene VIII is expressed in the presence of the helper plasmid with a gene VIII knockout, complementation of gVIII occurs and all the viral proteins necessary for phage particle production are present. In this case we expect the messaging phagemid to be sent as a DNA message. When expression of gene VIII is not induced, we expect to see no viral particle production and no DNA messaging.

Controlled Modification and Retransmission of a DNA Message

We sought to combine control over transmission and modification of a DNA message to allow receiver cells to modify a received DNA message and then retransmit it. In the scheme we developed, there are three populations of E. coli that will be co-cultured: the sender population, which transmit a DNA message; the primary receiver population, which receive a message and in the presence of a particular stimulus modify it and retransmit it; and a secondary receiver population, which exhibit a detectable behavior (ie fluorescent protein production) when they receive a modified message (Fig 5).

Figure 5. In our scheme, the sender population sends a DNA message that is received by the primary receiver population. In the presence of a particular stimulus, the primary receiver population modifies the DNA message by flipping an invertible promoter switch and retransmits it. A secondary receiver population will exhibit a detectable behavior (eg fluorescent protein expression) when it receives the modified message.

For primary receiver cells to control retransmission of a DNA message, they should have a helper plasmid with a gene VIII knockout as described in the previous section on controlled transmission. This knockout helper plasmid would produce viral particles only when M13 gene VIII is complemented. To make the DNA message modifiable by primary receivers, an invertible promoter switch should be placed on the messaging phagemid. We wanted retransmission to be part of the instructions in the DNA message, so our design places gene VIII on the messaging phagemid under control of the invertible promoter switch. If integrase is under an inducible promoter in primary receiver cells, induction will cause expression of integrase, flipping of the switch, and expression of gene VIII. The knockout helper plasmid will thus be complemented and the messaging phagemid, with the switch flipped, will be packaged into viral particles and retransmission will occur. (To be added: figure X).

One concern for this design is that basal (uninduced) expression of integrase might cause the switch to flip, leading to production of viral particles containing the modified message even in the absence of induction. Since viral particles infect other cells, numerous receiver cells could become infected due to unwanted switch flipping in just one sender cell. Such amplification of error could be significant. To improve the robustness of the switch and prevent unwanted flipping, we devised a two-switch system wherein flipping of one switch is controlled by the flipping of a second switch. This two-switch system is described in the next section, and its application here is depicted in (To be added: figure X).

Reduction in Unwanted Flipping of an Invertible Promoter Switch Using a Double Switch System

A major difficulty in controlling any cellular behavior using gene expression from an inducible promoter is the issue of basal expression; that is, expression of a gene driven by an inducible promoter in the absence of induction. When an invertible promoter switch is controlled through induced expression of integrase, unwanted flipping of the switch due to basal expression of integrase is of particular concern because invertible promoter switches hold their state. To improve control over the flipping of a DNA switch, we devised a double switch system in which a first switch controls the flipping of a second switch. This system, described below, is expected to reduce flipping of a DNA switch due to leaky integrase expression.

References

Videos

Accomplishments

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Future Aspirations

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Results

Characterization of PhiC31 and Bxb1 invertible promoter switches

PhiC31 and Bxb1 invertible promoter switches were characterized using test constructs which utilize differential fluorescent protein expression to distinguish between the directionality of the promoter in its PB state and the RL states. These two states are determined by the expression of phage-encoded site-specific recombinase, namely, integrase as well as their corresponding reverse directionality factor or RDF. As outlined in the project description, PhiC31 or Bxb1 serine integrase alone mediates site-specific recombination between attachment (att) sites (attP and attB sites specifically), flanking each promoter switch in its PB state. Upon recombination, the orientation of the promoter within each switch is reversed and the switch is now is its RL state due to the production of recombinant product sites, attR and attL. Once the switch is in its RL state, expression of PhiC31 and Bxb1 recombination directionality factors (RDFs) in conjunction with PhiC31 and Bxb1 integrase expression allows the reversal of the invertible promoter switch back to its PB state. The recombination directionality factor reverses the directionality of the site-specific recombination mediated by integrase. Designing constructs which allow the expression of specific fluorescent proteins depending on the direction of the promoter within each promoter switch helped the development of an easy detectable system for characterizing both the PhiC31 and Bxb1 promoter switches as well as their corresponding integrases and RDFs. The characterization of PhiC31 and Bxb1 promoter switches was carried in the presence of both inducible and non-inducible expression of Phi C31 and Bxb1 integrases and RDFs.

Experimental design

1. Constructs

1.1. Multi-copy test constructs:

Multi-copy test constructs were constructed for the following promoter switches in their PB state (promoter switches flanked by attP and attB sites):

1. BBa_K1039001: Bxb1 Invertible Promoter Switch (Promoter J23119) – PB State (will be referred to as BS1 for simplicity)

2. BBa_K1039008: PhiC31 Invertible Promoter Switch (Promoter J23119) – PB State (will be referred to as PhiS1 for simplicity)

3. BBa_K1039009: PhiC31 Invertible Promoter Switch (Promoter J23118) – PB State (will be referred to as PhiS2 for simplicity)

Green fluorescent protein (GFP) was placed downstream of each promoter switch in its inverted orientation (BBa_K1039015). This allows for the promoter switch to transcribe GFP in its PB state. Red fluorescent protein (RFP) (BBa_J04450) was placed upstream of each promoter switch and was therefore transcribed only upon a directionally regulated site-specific recombination event on the attP and attB sites flanking the promoter switch. As mentioned before, this event is mediated by PhiC31 and Bxb1 integrases respectively and thereby results in the reversed orientation of the promoter (Fig. 1). The multi-copy test constructs were assembled via 3A assembly (Parts Registry Assembly Protocol) and sub-cloned into a Parts Registry plasmid, pSB4A5. Each test construct is flanked by the standard iGEM suffix and prefix. The multi-test constructs made include:

1) Bba_K1039025: Test construct for Bxb 1 Invertible Promoter switch (Promoter J23119). It includes iGFP (GFP in inverted orientation) downstream and RFP upstream of the promoter switch.

2) Bba_K1039027: Test construct for PhiC31 Invertible Promoter switch (Promoter J23119). It includes iGFP (GFP in inverted orientation) downstream and RFP upstream of the promoter switch

3) Bba_K1039028: Test construct for PhiC31 Invertible Promoter switch (Promoter J23118). It includes iGFP (GFP in inverted orientation) downstream and RFP upstream of the promoter switch.

1.2. Multi-copy Non-inducible Integrase-expressing constructs:

Two constructs for the constitutive expression of PhiC31 and Bxb1 integrases respectively, were assembled via Standard Assembly (Parts Registry Assembly Protocol). Genes encoding the PhiC31 and Bxb1 integrases (BBa_K1039012 and BBa_K1039003) were separately cloned downstream of a constitutive promoter and its corresponding ribosome binding site (K608002) in pSB1C3 (Parts Registry Standard vector) (Fig. 2). Each test construct is flanked by the standard iGEM suffix and prefix. The multi-test non-inducible integrase-expressing constructs include the following:

1) Bba_K1039030: PhiC31 integrase-expressing construct with a Promoter and RBS

2) Bba_K1039029: Bxb 1 integrase-expressing construct with a promoter and RBS.

1.3. Multi-copy Non-inducible Integrase and Recombination directionality factor- expressing constructs:

Constructs were assembled to allow constitutive expression of both integrase and recombination directionality factor simultaneously from a single promoter. This construct was assembled via Standard Assembly (Parts Registry Assembly Protocol) for both PhiC31 and Bxb1 integrases/RDFs respectively (Fig. 3). Each construct is flanked by the standard iGEM suffix and prefix. The multi-test non-inducible integrase and RDF producing constructs include:

1) Bba_K1039014: PhiC31 integrase and RDF expressing construct from a single promoter. Both genes have an associated ribosome binding site.

2) Bba_K1039007: Bxb 1 integrase and RDF expressing construct from a single promoter. Both genes have an associated ribosome binding site.

1.4. Inducible Integrase-Expressing constructs:

See “uOttawa collaboration”

1.5. Inducible Integrase and Reverse Directionality factor expressing constructs:

See “uOttawa collaboration”

1. Testing of Phi C31 and Bxb 1 Invertible Promoter switches (PB state)

Test constructs for Phi C31 and Bxb 1 invertible promoter switches (PB state) were individually transformed into a competent E. coli strain DH5α. After overnight growth (~16h) on LB agar plates (with appropriate antibiotics) at 37 degrees, specific colonies were selected and subsequently inoculated in 5 mL of Laurel Broth (LB) (containing appropriate antibiotics). The cultures were allowed to grow overnight (~16h) at 37 degrees. The culture was then pelleted at 13, 000 rpm for 1 minute and viewed under an appropriate UV filter to detect GFP expression. To characterize the invertible promoter switches in their PB state, ~500 ng of each test construct was co-transformed into a competent E. coli strain (DH5α) with its corresponding constitutive integrase-expressing construct (~500 ng). The cells were subsequently plated on LB agar (with appropriate antibiotics to maintain both plasmids) and allowed to grow for two days at 37 degrees (~36h). The growth period was chosen to allow adequate expression of the integrase which would consequently mediate a recombination event resulting in the reversed orientation of the promoter (RL state) within each switch and thereby drive the expression of RFP. Bacterial colonies grown on agar plates after two days were analyzed for RFP expression.

2. Testing of Bxb 1 Invertible Promoter switches (RL state)

After a site-specific recombination event mediated by integrase, the Bxb 1 invertible promoter switches were in their RL state due to the resulting attR and attL sites, which now flank each of the promoter switches. The RL state of each invertible promoter switch was indicated by RFP expression. To isolate each test construct (with the invertible promoter switch in its RL state) from the integrase-expressing construct present in the bacterial cell, an RFP-expressing bacterial colony from the co-transformation LB agar plate was isolated and grown in 3 mL of Terrific Broth (TB) for 6 hours at 37°C. Upon growth, it was transformed into the E. coli laboratory strain (DH5α) and subsequently grown on an LB agar plate containing appropriate antibiotics to select for the test construct (containing the invertible promoter switches). Note that the integrase was expressed from a plasmid with a different antibiotic resistance marker than the plasmid containing the promoter switches. After the colonies grew on the LB agar plate (containing appropriate antibiotics), the colonies were isolated and grown in Terrific Broth (TB) for 6 hours at 37°C. Subsequent mini-prep of cultures resulted in the isolation of the test construct from the bacterial cell. Characterization of the promoter switch in its RL state was carried out by co-transforming ~500 ng of each isolated Bxb 1 invertible promoter switch test construct with its corresponding Bxb 1 integrase and RDF producing construct into a competent E. Coli strain (DH5α). The cells were allowed to grow on LB agar plates (with appropriate antibiotics) for two days (~36h) at 37 degrees. The growth period allows for adequate simultaneous expression of both the integrases and RDFs, which thereby reverses the RL state back to its PB state. Bacterial colonies grown on LB agar plates (after two days) were analyzed for GFP expression. Note that PhiC31 Invertible promoter switches (RL state) could not be characterized due to time constraints.

1.6 Single Copy Test

An E.coli strain, HB101, does not have a prophage at the phi80 locus in it’s chromosome and was used for the single copy test. HB101 competent cells made in house were transformed with a helper plasmid, pInt80-649, that has a temperature sensitive replication of origin (SCI101) and the gene for lambda pir gene. These cells were made competent again as successful co-transformation was to follow. Meanwhile, the switch constructs were subcloned into an integrative plasmid, pBBIntPhi-J23118, that has a lambda pir origin of replication (R6K). The HB101 competent cells containing pInt80-649, were transformed with sub cloned pBBIntPhi-J23118 with the switch constructs. This assured the propagation of the integrative plasmid as it had the lambda pir protein being made from the helper plasmid all in one culture. Clones were then grown in liquid media at 37C to inactivate the temperature sensitive plasmid. Clones were further streaked purified and were grown at 43C over night. This selected for clones that should theoretically only have the integrative plasmid containing the insert of interest (the switches flanked by reporter genes). To confirm proper integration of insert into the bacterial chromosome, colony PCR was performed on several clones of each switch construct. The colony PCR resulted in no product, and because of time constraints the single copy test was found not to be successful. Ideally, using the primers provided by Zucca et al., 2013 would help anneal upstream of the Phi80 chromosomal attB site and in the R6K origin respectively. The expected amplicon would be 452bp and would indicate the correct integration position, while negative clow would show no amplicon. Additionally, to identify multiple tandem copies of the integrated switches flanked with reporter genes, can be achieved by using another pair of primers also provided by Dr. Zucca. This pair of primers would anneal in opposite directions in the R6K origin of replication and in the upstream region of the cloning sire. A 572 bp amplicon would prove that atleast two tandem copies are present in the genome.

Gene VIII Complementation Test

To accomplish our goal of controlling DNA messaging, we sought to control M13 viral particle production by removing M13 gene VIII from the helper plasmid and placing it under an inducible promoter on a separate construct. M13 protein VIII, the product of gene VIII, is the major coat protein of the M13 bacteriophage, so viral particle production and DNA messaging should be possible only when gene VIII is expressed and protein VIII is present (see the Design page). As a step toward this goal, we first sought to demonstrate that viral particles could be produced when a helper plasmid missing gene VIII is complemented by a copy of gene VIII on a separate construct (See Figure xx)

Figure --: The messaging phagemid (A) contains the M13 packaging sequence, an RFP indicator, and M13 gVIII which will complement the helper plasmid (B), which contains the remaining M13 genes, in order to produce viral particles.

After making our constructs, we set out to determine if our helper plasmid with gene VIII knockout (BBa_K1039017) could be complemented with a messaging phagemid consisting of M13 origin (BBa_K314110) - RFP expression cassette (BBa_J04450) - Constitutive Promoter and Ribosome Binding site + M13 gene VIII (BBa_K1039020) in pSB1C3. We expected gene VIII to be expressed from the messaging phagemid and to complement the helper plasmid with gene VIII knockout. With a complete set of functional proteins, the virus should be able to assemble itself and package the messaging phagemid through recognition of the M13 ori to successfully deliver the message to the receiver population. Chloramphenicol resistance (from the pSB1C3 backbone) and RFP expression should be detectable in receiver cells that have received the DNA message.

To test the complementation of gene VIII, we used E. coli βDH10B containing messaging phagemid and helper plasmid as a sender population, and we used E. coli JM109 containing a constitutively expressed GFP expression cassette (BBa_I20260) in pSB3K3 (kanamycin-resistant) backbone as a receiver population. The senders, E. coli βDH10B, require diaminopimelic acid (DAP) as supplement for growth in LB media. The receivers, E. coli JM109 are F+ and do not require this supplement. (Recall that receivers must be F+ for delivery of a DNA message by an M13 particle.) This allows counter-selection against sender cells by growing on LB media with no DAP supplementation. Receiver cells that have received the message can be selected using chloramphenicol and should also appear red.

Figure --: Schematic representation of M13 complementation test.

Co-culture of sender and receiver populations

Message transmission was tested by co-culturing sender and receiver populations before selecting for successful transmission. During the co-culture, M13 particles containing the DNA message should be secreted by sender cells and should deliver the message to receiver cells.

Exposure of receiver population to filtrate from sender culture

Since the message is transmitted through viral particles, sender cells should not need to be in contact with receivers for message transmission; presence of message-carrying viral particles should be enough. We therefore also tested message transmission by exposing receiver cells to culture filtrate from sender cells, which should contain viral particles secreted by the senders that can deliver messages to receivers.

Controls

As a positive control, we used senders carrying a complete helper plasmid (gene VIII present) and a messaging phagemid carrying the M13 origin of replication and an RFP expression cassette (BBa_K314110- BBa_J04450). With the helper plasmid intact and all phage proteins expressed, we expect the phage machinery to recognize the M13 origin and package the messaging phagemid to be sent to the receiver population.

As a negative control to demonstrate the necessity of the M13 origin, we performed an experiment identical to the positive control using a messaging phagemid that is missing the M13 origin. Without the M13 origin, we expect no transmission of the messaging phagemid. We also performed a negative control for the gene VIII complementation experiment wherein the messaging phagemid was missing the M13 ori. As a negative control to demonstrate the necessity of gene VIII for viral packaging, we performed an experiment identical to the gene VIII complementation experiment, but with the messaging phagemid lacking gene VIII (ie no gene VIII was present in the system). As a negative control to demonstrate the necessity of having both a helper plasmid and a messaging phagemid for successful transmission, we also included experiments wherein senders contained only a messaging phagemid or only a helper plasmid. In these cases we expected no message transmission. As a negative control to demonstrate the necessity for F+ receivers, we repeated all experiments using DH5α (F- strain) as the receiver population. We expected no successful messaging with F- receivers, because the F pilus, which is only present in F+ strains, is required for the mechanism of message delivery using M13 particles.

In addition, we plated senders and receivers individually on our selection plates to check for contamination. These controls were used in both the co-culture and filtrate experiments.

Experimental Design

For the purposes of the complementation tests, the following constructs were sequentially transformed into βDH10B:

1. HPdO (BBa_K1039016) and pSB1C3-M13 ori- RFP cassette (BBa_K314110- BBa_J04450) 2. HPdO (BBa_K1039016) and pSB1C3-RFP cassette (BBa_J04450) 3. HPdO Δ gVIII (BBa_K1039017) and pSB1C3- M13 ori - RFP- Constitutive promoter + RBS - gVIII (BBa_K314110- BBa_J04450- BBa_K1039020) 4. HPdO Δ gVIII (BBa_K1039017) and pSB1C3- RFP- Constitutive promoter + RBS - gVIII (BBa_J04450- BBa_K1039020) 5. HPdO Δ gVIII (BBa_K1039017) and pSB1C3 - M13 - RFP cassette (BBa_K314110- BBa_J04450) 6. HPdO (BBa_K1039016) 7. HPdO Δ gVIII (BBa_K1039017) 8. pSB1C3- M13 ori - RFP- Constitutive promoter + RBS - gVIII (BBa_K314110- BBa_J04450- BBa_K1039020) 9. pSB1C3- M13 - RFP cassette (BBa_K314110- BBa_J04450) 10. pSB1C3- RFP- Constitutive promoter + RBS - gVIII (BBa_J04450- BBa_K1039020) 11. pSB1C3- RFP cassette (BBa_J04450)

The following construct was transformed into JM109 and DH5α:

A. pSB3K3- GFP cassette (BBa_I20260) in JM109 strain B. pSB3K3- GFP cassette (BBa_I20260) in DH5α strain

Please refer to Table 1.1 under protocols for antibiotic concentrations.

Please refer to Table 1.1 under protocols for antibiotic concentrations.

• Grow cultures 1-11 and A-B individually in LB with appropriate antibiotic supplements until OD600 ≈ 0.7 (± 0.1) • Centrifuge cultures and wash pellet 3 times with LB • Resuspend 1-11 in appropriately supplemented media but without Cm since the receiver population is not Cm resistant • Resuspend A-B in LB DAP since some of the senders are not Km resistant • Incubate at room temperature with shaking for 6-10 h • Co-culture senders and receivers in LB DAP (Km only for senders 1-7) broth in a 2:1 ratio of senders to receivers to ensure that a sufficient amount of message is present • Incubate at room temperature with shaking for 6-10 h • Centrifuge and wash pellet 3 times with LB to remove DAP from the media • Resuspend in LB Km Cm • Subculture with a dilution factor of 1/100 into LB Km Cm so only receivers carrying the messaging phagemid and the GFP plasmid are able to grow • Incubate over night at 37 °C with shaking • Dilute culture 10-6 times • Plate 100 μL of diluted culture onto LB Cm 20 Km 25 agar

Filtrate experiment

• Grow cultures 1-11 and A-B individually in LB with appropriate antibiotic supplements until OD600 ≈ 0.7 (± 0.1) • Centrifuge cultures and wash pellet 3 times with LB • Resuspend 1-11 in appropriately supplemented media but without Cm since the receiver population is not Cm resistant • Resuspend A-B in LB DAP since some of the senders are not Km resistant • Incubate at room temperature with shaking for 6-10 h • Collect filtrate of senders by centrifuging cultures at room temperature • Filter sterilize through 0.45 μm filter to remove remaining bacterial cells in the filtrate • Infect the receiver population by mixing it with the sender filtrate • Incubate at room temperature for 6-10 h • Plate all cells on LB Cm 20 Km 25 agar

Table here Table here Table here Table here Table here

Genotype of Strains

DH5α F- endA1 glnV44 thi-1 recA1 relA1 gyrA96 deoR nupG Φ80dlacZΔM15 Δ(lacZYA-argF)U169, hsdR17(rK- mK+), λ–

JM109 endA1 glnV44 thi-1 relA1 gyrA96 recA1 mcrB+ Δ(lac-proAB) e14- [F' traD36 proAB+ lacIq lacZΔM15] hsdR17(rK-mK+)

βDH10B F- endA1 recA1 galE15 galK16 nupG rpsL ΔlacX74 Φ80lacZΔM15 araD139 Δ(ara,leu)7697 mcrA Δ(mrr-hsdRMS-mcrBC) λ-

Plasmids Used

pSB1C3

pSB3K3

HPdO

Plasmids used for Construction

pSB1A3

pSB4A5

Conclusions

Conclusions Conclusions Conclusions Conclusions Conclusions Conclusions Conclusions Conclusions Conclusions Conclusions Conclusions

BioBricks

Bba_K1039000	Φ attP site
Bba_K1039001	BXB1 pb switch J23119 promoter
Bba_K1039002	BXB1 pb switch J23118 promoter
Bba_K1039003	BXB1 integrase
Bba_K1039004	BXB1 lr switch J23119 promoter
Bba_K1039005	BXB1 lr switch J23118 promoter
Bba_K1039006	BXB1 RDF
Bba_K1039007	BXB1 integrase and RDF
Bba_K1039008	ΦC31 pb switch J23119 promoter
Bba_K1039009	ΦC31 pb switch J23118 promoter
Bba_K1039010	ΦC31 lr switch J23119 promoter
Bba_K1039011	ΦC31 lr switch J23118 promoter
Bba_K1039012	ΦC31 integrase
Bba_K1039013	ΦC31 RDF
Bba_K1039014	ΦC31 integrase and RDF
Bba_K1039015	iGFP
Bba_K1039016	Hpdo backbone
Bba_K1039017	Hpdo with no gene 8
Bba_K1039018	gene 8 of M13 virus
Bba_K1039019	RBS+gene 8 of M13 virus
Bba_K1039020	J23104+RBS+gene 8 of M13 virus
Bba_K1039021	loc+BXB1int+key+lock+BXB1 RDF
Bba_K1039022	loc+PhiC31int+key+lock+phiC31 RDF
Bba_K1039023	loc+BXB1int+key
Bba_K1039024	loc+BXB1int+key
Bba_K1039025	BS1TC
Bba_K1039026	BS2TC
Bba_K1039027	ΦS1TC
Bba_K1039028	ΦS2TC
Bba_K1039029	BXB1 integrase with the Promoter and RBS
Bba_K1039030	ΦC31 integrase with the Promoter and RBS
Bba_K1039031	BXB1 att P
Bba_K1039032	BXB1 att B
Bba_K1039033	BXB1 att R
Bba_K1039034	BXB1 att L
Bba_K1039035	ΦC31 att B
Bba_K1039036	ΦC31 att R
Bba_K1039037	ΦC31 att L

Ottawa's Collaboration

This year Waterloo iGEM collaborated with Ottawa iGEM. Ottawa team required help with Mathematical Modelling. In exchange Ottawa team was able to help us build the following constructs:

Promoter-LacI cassette-lock-Bxb1 integrase-Transcriptional Terminator-Promoter- Key-Transcriptional Terminator-Promoter- Lock- Bxb1 RDF

Promoter-LacI cassette-lock-PhiC31 integrase-Transcriptional Terminator-Promoter- Key-Transcriptional Terminator-Promoter- Lock- PhiC31 RDF

Promoter-LacI cassette-lock-Bxb1 integrase-Transcriptional Terminator-Promoter- Key-Transcriptional Terminator

Promoter-LacI cassette-lock-PhiC31 integrase-Transcriptional Terminator-Promoter- Key-Transcriptional Terminator

Notebook

Switch Modelling

x y z

Population & Infection Modelling

a b c

Phage Particle Production Modelling

a b c

The University of Waterloo’s iGEM – Human Practices team is a diverse team whose goal is to raise awareness on issues regarding synthetic biology. In addition, the team also provides the student community information about the latest in the research area of synthetic biology to help the community make informed, accurate and fact-based opinions. Our goal is to strengthen the bridge between the community and their knowledge of synthetic biology along with eliminating misconceptions regarding synthetic biology.

In the past year, this team gained valuable experience and information through the projects they worked on. Each project provided more insight on how informed the student community is on the topic of synthetic biology. This further helped us plan out activities that help us achieve our goal.

One of the main purposes behind the projects this year to enrich, educate and empower the student community. To achieve this goal, various activities were planned to inform the student community about the field of synthetic biology, it’s potentials and how it affects the world around us. These activities provide fundamental knowledge of synthetic biology and it’s uses, allowing the participants and the viewers to form an informed, accurate and fact-based opinion about the topic.

T.I.L.

iGEM is a community of people passionate about synthetic biology – how can we best convey this while reaching out to the public? Sometimes reading papers and textbooks doesn't quite do it for understanding an idea. As students, we know it can be difficult to grasp some concepts we’re not familiar with. So what’s a better way to communicate an idea? Could social media be the answer? That was the idea behind the VLOG series TIL: Syn Bio.

These series are a quick and effective way to convey the ideas and passion of synthetic biology. The series has many episodes that highlight various aspects of synthetic biology through a mixture of one-on-one videos and animated style videos. The series begin with episodes explaining “What is Synthetic Biology?, “Fundamental Advances” and “Cell-to-Cell Communication” (Waterloo iGEM’s 2013 project). This phase of the series is important to orient the viewers and provide some background information. During the second part of the series, the team takes a fun twist. Using the TIL: Synthetic Biology outreach event footage to compare the viewpoints of students and professors on various topics relating to synthetic biology. The footage from this event is used for addressing many factors associated with the idea of synthetic biology. These factors range from the background knowledge to stigma associated with synthetic biology and from the regulations needed to its future potential.

The series begins with these six videos, leaving the rest of the series to be shaped by viewers. Ultimately, viewers engage with the team about what they want to see in future videos, ask questions they want answered and connect with information from a variety of sources.

The TIL: Synthetic Biology outreach event (used as part of the video series) was well-received. The team came prepared with questions to ask passing students. Students were also given 4-5 days notice via Facebook. The idea behind this aspect of the video was to have it be a surprise. Questions like "do you support GMOs?", "would you eat modified fruit/meat?", "who should be able to practice synthetic biology/should it be open sourced?" and many more were asked. The team was in for some surprises with the diversity of knowledge on campus! We hope incorporating the footage into our series will give participants a fun look into their experience, which they can easily share with their friends and family. Overall, we hope that the team's work will inspire more leaders to take part and contribute to the advances in synthetic biology, regardless of their academic or professional background.

Intent to Invent

Intent to Invent was hosted on March 07, 2013 at the University of Waterloo’s Quantum Nano Center. The purpose of the event was to:

1. Connect the students to experts in 3 key industries that use synthetic biology in their processes: Agriculture, Health and Pharmaceuticals.
2. Bridge the level of discomfort a scientist has in regards to business.
3. To encourage entrepreneurship within the scientific community by delivering resourceful content from industry experts.

The event promoted open panel discussions of emerging technologies in biotechnology and other advanced biological fields within the 3 industries. Students got a chance to see how synthetic biology is the connected to entrepreneurship, innovation and commercialization. They learned about the industry perspectives and barriers faced by biological companies at different stages in their business model. This talk also encouraged entrepreneurship within the scientific community by delivering resourceful content form industry experts. Each speaker gave a 20-minute mini lecture on topics including: Clinical Trial Drug Development, Commercialization of Biomass and Energy Products and Entrepreneurial Barriers for Biotechnology Companies.

Steve jobs once said, “I think the biggest innovation of 21st century will be the intersection of biology and technology. A new era is beginning, just like the digital one…”. Through sessions such as Intent to Invent, Waterloo iGEM hopes to enrich the experience of science enthusiasts as well as those just curious about synthetic biology and it’s potential. By connecting these students to industry experts, we were able to gage their interests in an innovative and entrepreneurial aspect of science. Many students showed interest in learning more about the bridge between science and business in the future. iGEM received good feedback regarding Intent to Invent, as many students felt that the information they learned was very valuable. Waterloo iGEM provided many students the appropriate connection and information they need to start connecting the scientist in them with the businessman/businesswoman in them.

VeloCity Science

We want to inspire young people to eliminate the gap between science and business. The conventional education system does not provide for such activity. There is a job unemployment crisis throughout North America, and from the past experience, this is the perfect time to pursue this. It is time to do what we have done to the IT industry back in the 80s, but with synthetic biology this time.

Economic downturns have proven to be the best time for entrepreneurship. The perfect storm is brewing. The infrastructure is there to support initiative like this. We have bright young people hungry to make changes to the world.

What has University of Waterloo done to support this movement? We have created an entrepreneurship program that brings together the right business resources (networks, mentorship, legal and financial services, etc) and the right technical resources (wetlab space, consumables and equipment) to create kick-ass biotechnology start-ups.

But that’s not all. Above of all these resources, it is the sense of community that is crucial for the success of these entrepreneurs. The University of Waterloo has proven time and time over in providing a strong sense of community to our entrepreneurs through the programs like Accelerator Centre, Communitech Hub, and VeloCity.

That’s the story of VeloCity Science. And, we are just starting to write it.

Laboratory

Intent to Invent

Safety

All experiments are carried out in a BL2 certified lab. Researcher safety when using E. coli, would not be compromised in safety issues due to use of M13. It poses no threat at all to humans. While, the E. coli strain used was relatively harmless, treatment of possible infections may potentially be affected by the antibiotic resistance. Furthermore, spontaneous mutations which result in increased infectivity may result. However, measures and precautions suggested by the Canadian biosafety guidelines were taken to minimize even the slight chance of infection. Additionally, the working conditions of the lab is already above the recommended safety level of BL1 for usage of M13 viruses. Every member of the team has been trained with safety modules and went through a week of lab training and continuous oversight from the Advisors and his graduate students in the lab. All lab members, including graduate students or other students that were working in the lab, wore appropriate PPEs and disposed all consumable in appropriate biological waste boxes. All surfaces were wiped down with ethanol after use and all glassware was washed immediately after their usage.

The design of the project does not call for release into the public. Additionally, the project design does not produce any harmful products. Through it is possible that the construct could get released to the general public accidentally. But, the product of the constructs only produce fluorescent proteins and it can only be used in a controlled setting with a certain type of chemical present in the environment, thus making it ineffective when released to the public. Because safety of the public and the lab members is our utmost concern, we have ensured that all wastes are thrown out appropriately and autoclaved so that accidentally release would never occur.

There are no additional risks posed by our projects compared to other general BL1 lab concerns. Our bacteria are not pathogenic and are unable to survive outside of the lab environment, because they are unable to effectively compete with other organisms in nature. As stated above, all wastes are discarded according to the Waterloo standards and autoclaved.

There is no potential for harm to human health through use of our constructs, as described above. There is therefore no risk of malicious use.

Our constructs pose no threats to human health, as described above, and scaling up would not change this. Our project is a "fundamental advance" that contributes to the coordination of population-level cellular behavior by allowing messages to be sent between populations of E. coli cells. However, many additional layers of complexity in engineering would be required to use our method to enable pathogenic or otherwise dangerous behaviors in populations of cells.

The cell to cell communication project does include packaging viral particles. Although there are only some proteins of the M13 virus that are packaged and are therefore not a safety risk. M13 is not a safety risk even if its whole genome is packaged. Our project poses no threat to safety and thus we haven't implemented any of these mechanisms.

All the lab and design team members successfully passed the following safety training: Employee Orientation Training Session: https://info.uwaterloo.ca/infohs/hse/online_training/employee-orientation/Staff%20Orientation.swf Workplace Violence and Harassment Training: https://info.uwaterloo.ca/infohs/hse/online_training/workplace_violence/workplace_violence.html General Laboratory Safety: https://info.uwaterloo.ca/infohs/hse/online_training/lab_safety/lab_safety_course.html WHMIS: http://www.safetyoffice.uwaterloo.ca/hse/lab_safety/index.html Laboratory BioSafety Training: https://info.uwaterloo.ca/infohs/hse/online_training/biosafety/biosafety.swf

The BioSafety Guidelines followed by uWaterloo iGEM team can be found here: http://www.safetyoffice.uwaterloo.ca/hse/bio_safety/legislation.html

University of Waterloo has a Biosafety Committee and can be found here: http://www.safetyoffice.uwaterloo.ca/hse/bio_safety/bsc.html. Although the project has not been discussed with the Biosafety Committee, it has been discussed with several faculty members and has been found to have no risks. Furthermore, the laboratories operating at the University of Waterloo have obtained permits from the Bio-Safety Committee in order to perform intended research. Since the Waterloo iGEM team performs all laboratory work in a parent lab under the guidance of the Masters and PhD students of that lab, the permits obtained by the parent lab cover the projects carried out in the lab.

Canada has very well established biosafety regulations and guidelines which can be found here: http://www.phac-aspc.gc.ca/lab-bio/

The laboratory we work on cell to cell communication project is rated level 1.

E.coli strains that Waterloo iGEM team works with falls within the risk level 1. Additionally the laboratory we operate in is certified for work with the above listed risk group of the E.coli.

Administrators

Lab & Design

M13 Group

BxB1 Group

Φ C31 Group

Mathematical Modelling

Human Practices

Advisors

Graduate Student Advisors