Ftsz-Mediated Fission of a Cuboid Bacterial Symbiont
25 Pages Posted: 13 Jul 2021 Publication Status: PublishedMore...
Less than a handful of cuboid and squared cells have been described in nature which makes them a rarity. Here, we show how Candidatus Thiosymbion cuboideus, a cube-like gammaproteobacterium, reproduces on the surface of marine free-living nematodes. Morphometric analysis showed that most non-dividing Ca . T. cuboideus cells are squared and 1.3 μm-thick on average. Immunostaining of symbiont cells with an anti-fimbriae antibody revealed that they are host-polarized, as these appendages exclusively localized at the host-proximal (animal-attached) pole. Moreover, by applying a fluorescently labelled metabolic probe to track new cell wall insertion in vivo , we observed that the host-attached pole started to septate before the distal one. Proximal-to-distal insertion of new cell wall material at the septum displayed a similar localization pattern as the tubulin homolog FtsZ. Although this has been shown to arrange into squares in synthetically remodelled cuboid cells, here we show that FtsZ may also mediate the division of naturally occurring ones. This implies that, even in natural settings, membrane roundness is not required for FtsZ function.
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