Team:Groningen/Lab/experiments

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Biofilm Growth on different materials

To find out if the bacillus subtilis strain used can form a biofilm on material often used in implants, an experiment was set up.

The material were placed in a plate with Sgg medium. The material were partially submerged in the medium and the plate was inoculated with the bacillus subtilis strain. The plate is left in a 27 C environment for 5 days. At the end of this period the amount of growth on the material is measured. After 5 day there is a 3 cm growth from the medium upward on the titanium upward of biofilm, on plastic there was no growth.

Figure 1: Titanium plate with 3 cm growth.


Figure 2: Plastic in Sgg medium, no growth on the plasic came about.


Motility assay

A motility assay is done for Bacillus subtilus of different knockout strains as wel as a wild type strain.

This is to determine how different the knockouts move compared to the wild type B. subtilus.

The results will be used to determine if the temperature controlled strain works as desired, moving more as a CheY knockout in warm environments and more as a wild type in cold environments.

The design of the motility assay is a simple one. LB agar Plates are made with the normal amount of LB-broth as nutrients but with a reduced amount of agar.

Different concentrations are used to find out the optimal amount of agar to show the motility. Low concentrations are needed to allow movement through the medium but too low and the observed movement can be caused by dispersal and turbulence during movement. The concentrations that are used are, 0.4% agar and 0.7% agar.

The plates are inoculated in the center with the strain that is to be tested. This is done with … ul of liquid culture of a OB of … .

For each strain 9 plates of each agar concentration is made. Three of the plates are placed in a 37 C stove and three placed in a 30 C stove and three placed in a 27 C stove to grow.

The colonys are left to grow for 16 hours. Then how the colonies spread on the plates are observed every hour. The bacteria that are more motile should spread out over the agar creating a clouwdy look while the non- motile bacteria should stay in the center, close together.

How quickly the bacteria spread from the center to the edge can be used as an indicatore of how fast they move.