Bacteria shapes11/2/2022 ![]() ![]() ![]() There are probably many reasons a cell is the shape it is. We now look more closely at bacterial shape and ask the question: ‘Is there some logical or evolutionary reason why rod-shaped bacteria have the shape they do?’ More specifically we ask, for example, why does Escherichia coli have the shape it does? Why isn't it longer or shorter? 1.1 A priori considerations on cell shape Since the optimal shape is independent of actual size (within large bounds), it is further proposed that hydrodynamic efficiency considerations support the proposal of constant shape over a range of sizes for rod-shaped bacteria.Ĭell shape, Motility, Bacteria, Escherichia coli, Hydrodynamic efficiency 1 IntroductionĪfter we first notice that rod-shaped bacteria are somewhat longer than wide, we generally take no more notice of exactly why the observed length-to-width ratio is what it is. It is also found that spherical cells are very inefficient in movement through liquid, while longer cells of a fixed size are still relatively efficient in moving through liquids. As this is in approximate agreement with the observed shape of bacteria such as the Enterobacteriaceae, we conjecture that the current observed shape of these bacteria may have been determined, in part, to obtain the most efficient shape for moving through liquids. For a cell of a given size, a minimum exists in the force required to move through any liquid when the length of the cell is approx. the length-to-width ratio of a bacterial cell, that allows a bacterial cell to move most efficiently through liquid. We have calculated the optimal shape, i.e. ![]()
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