摘要：SummaryLess than a handful of cuboid and squared cells have been described in nature, which makes them a rarity. Here, we show howCandidatusThiosymbion cuboideus, a cube-like gammaproteobacterium, reproduces on the surface of marine free-living nematodes. 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 labeled metabolic probe to track new cell wall insertionin vivo, we observed that the host-attached pole started septation before the distal one. Similarly,Ca.T. cuboideus cells immunostained with an anti-FtsZ antibody revealed a proximal-to-distal localization pattern of this tubulin homolog. Although FtsZ has been shown to arrange into squares in synthetically remodeled 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.Graphical abstractDisplay OmittedHighlights•Ca.T. cuboideus cells are cuboid•Septation is host oriented inCa.T. cuboideus•FtsZ localization pattern recapitulates that of new PG insertion•FtsZ polymerizes into either straight or sharp-cornered filamentsMicrobial symbiosis, Bacterial cell shape, Bacterial cell division
