Nuclear and Cell Division in Filamentous Bacteria

GROWTH in unicellular bacteria usually takes place as a sequence of events culminating in cell division^1–6. In some cases, however, bacteria grows in chains (referred to here as filaments). Two reasons have been put forward for this: either the individual segments of a filament are complete cells in which the timing of separation from adjacent segments is an imprecise event, not coordinated with overall growth, or the production of filaments may be a controlled process which is a prerequisite to cell division. There is some support for the first possibility⁷, but more recently it has been observed that the chain length of filamentous bacteria depends on the growth medium^8,9. Here we report further evidence that in the bacterium Bacillus subtilis the production of filaments of up to sixteen nuclei is part of a programme of events necessary for the maintenance of particular rates of cell division and that the structure and physiology of this bacterium can be explained along the same lines as those of the models describing growth in the unicellular intestinal bacteria Escherichia coli and Salmonella typhimurium.