The 3D architecture of the bacterial chromosome

A bacterial chromosome is so long that it must be highly compacted and folded to stand within the cellular space. Genetic studies coupled with fluorescence microscopy showed that it is well organized into isolated domains. These domains also move with order when the chromosome is duplicated and the two new chromosomes are separated each in one half the dividing cell.

But 3D images of the chromosome within its intact cell were still very difficult to obtain due to the limitations of the current microscopy technics. The folding of the chromosome in space, its functional architecture have thus remained unclear.

A recent study shows such images. Thanks to a cryo-electron tomographic analysis, of the 3D architecture of the chromosome of the bacterium Bdellovibrio bacteriovorus. clearly appears. The salient observation is the versatile nature of this architecture: The chromosome can take several but very different shapes (twisted spiral vs. compact) providing the bacterium with different behaviors.

This study reinforces the idea of a pivotal role for one particular proteins called MreB. MreB is more and more thought to be a major actor in several cellular processes like the elongation, the nucleoid organization, the chromosome segregation, the chemoreceptor localization.

Reference:

Spiral architecture of the nucleoid in Bdellovibrio bacteriovorus
C. Butan, L.M. Hartnell, A.K. Fenton, D. Bliss, R.E. Sockett, S.Subramaniam and J.L. S. Milne
J. Bacteriology, 2010 Dec 10.

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The 3D architecture of the bacterial chromosome