Bacterial minimalism

Minimalism in microbiology could be interpreted as a reduction in cell size or a reduction in genome content. Three genomes this month illustrate both of these interpretations. Bdellovibrios are small cells, perhaps because the bdellovibrio life cycle involves entering into, and feeding inside, a host bacterium, which is often as small as 1 μm in diameter. However, even small bdellovibrio cells have a relatively large genome of 3.7 Mb, which is presumably necessary to encode the information that is required for their complicated life cycle. By contrast, mycoplasmas and phytoplasmas, which also reside inside a host cell, have a reduced minimal genome content. Examples of mycoplasma and phytoplasma sequences have recently been published, which could provide further insights into the minimal information requirements for microbial life.