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Team:Newcastle/Modelling/CellShapeModel
From 2013.igem.org
Contents |
Cell Shape Model
Background
One of our research themes focuses on the ability of L-form bacteria to fit the mould and/or fill spaces by growing into them. We would like to explore the biophysical properties of the cell and the limits of the cell size the L-form can grow to before dividing by constructing a 2-dimentional cell model.
The shape of the bacterial cell is usually determined by the structures of the cell wall and bacterial cytoskeleton. Cell wall of B.subtilis is a thick layer of peptidoglycan which contains cell-wall proteins, techoic and lipotechoic acids. Peptidoglycan is a rigid structure which helps to protect the cell from osmotic pressure and mechanical damage. It also helps the cell to maintain a constant shape, while does not specifically define it. This role is played by the cytoskeleton. Bacterial cytoskeleton is largely similar to that of eukaryotes. It comprises of three types of protein structures: FtsZ, MreB and crescentin (only present in certain species) which are homologous to eukaryotic tubulin, actin and intermediate filaments respectively. These proteins also perform other functions in the cell, usually they are involved in cell growth and division and therefore are often essential for the cell's survival. The communication between the two regulatory components is assured by a series of membrane-associated enzymes (penicillin binding proteins). (Cabeen, Jacobs-Wagner, 2005)
Because the L-forms lack the peptidoglycan cell wall, cells naturally adopt the most energetically favourable shape (i.e. sphere) regardless of the cytoskeleton structure. With protoplasts (cells with chemically digested cell wall), the growth, variation in shape and division is restricted due to the limited amount of the cell membrane which simply ruptures if the pressure inside the cell increases. The L-forms created with our bio-brick will have a mutation in the MurE gene which causes spontaneous increase in production of the IspA gene product which results in increased synthesis of the cell membrane. This stabilises the cell and allows for growth and division.
