Novel mechanism for cell division identified in mycobacteria

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Researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL; Lausanne, Switzerland) have discovered that cell division in mycobacteria may be linked to inherited cell surface markers, morphological landmarks termed wave troughs, which are to-date the earliest observed marker of division sites.

It is known that most rod-shaped bacteria divide by splitting centrally into two, a process that demands precise control. In bacteria this process involves cell-systems such as nucleoid occlusion and the ‘minicell’ system, which localizes the site of division.

However, some bacteria – such as mycobacteria – lack homologues of these proteins, and in these species it has been unclear how the cell division site is selected. In this study, recently published in Nature Microbiology, the team observed a novel undulating wave pattern on the cell surface of mycobacteria and demonstrated that these markers correlated to future division sites.

The researchers combined optical and atomic force microscopy in a custom-built instrument, and focused their attentions on investigating Mycobacterium smegmatis, a relative of the pathogenic strain M. tuberculosis.

The team created time-lapses of M. smegmatis growing and dividing across multiple generations, observing patterns of wave-like forms along the length of the bacteria that corresponded to division sites.

Senior author Georg Fantner EPFL commented: “This experiment constitutes the longest continuous atomic force microscopy experiment ever performed on growing cells.”

Another author from EPFL, John McKinney, added: “It illustrates the power of new technologies not only to analyze the things we already knew about with greater resolution, but also to discover new things that we hadn’t anticipated.”

The team reported that the roughly repeating wave pattern had an average wave-length of approximately 1.8 μm. The time-lapses demonstrated that daughter cells inherit the patterns, with wave-troughs forming up to three generations before they are used as division sites.

These reported morphological features present the earliest known landmark of future division sites in bacteria, according to the authors. Looking forwards, the team hopes to identify the underlying mechanisms behind these wave-like cell markers.

Sources: Eskandarian HA, Odermatt PD, Ven JXY et al. Division site selection linked to inherited cell surface wave troughs in mycobacteria. Nat Microbiol. 2 (17094), doi:10.1038/nmicrobiol.2017.94 (2017); https://actu.epfl.ch/news/discovery-of-a-new-mechanism-for-bacterial-divisio/

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