FtsZ-mediated fission of a cuboid bacterial symbiont

Abstract

Summary 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. 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 insertion in 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.

Previously uncharacterized rectangular bacterial structures in the dolphin mouth

“…In some RBSs, the neighboring DNA band pairs appeared "H"-like (Fig. 1g, white arrow), suggesting two rod-shaped cells in the process of division along a longitudinal axis with the DNA bands undergoing segregation 27 . RBSs clustered into two morphotypes based on the dimensions of the rectangular units (Fig.…”

“…Known rectangular cells from this family include Haloquadratum walsbyi 24 , Haloarcula quadrata 25 , and members of the pleomorphic genus Natronrubrum 26 . FtsZ-based fission has recently been observed in the cube-shaped nematode symbiont Candidatus Thiosymbion cuboideus 27 and additional rectangular cells believed to be bacterial or archaeal have been discovered in high salinity environments but not taxonomically identified 28 . Among eukaryotic microorganisms, diatoms can have a rectangular appearance when visualized in two dimensions, although these cells are cylindrical rather than rectangular prisms 29 .…”

Previously uncharacterized rectangular bacterial structures in the dolphin mouth

“…In some RBSs, the neighboring DNA band pairs appeared “H”-like ( Fig. 1g , white arrow), suggesting two rod-shaped cells in the process of division along a longitudinal axis with the DNA bands undergoing segregation 26 . RBSs clustered into two morphotypes based on the dimensions of the rectangular units ( Fig.…”

“…Known rectangular cells from this family include Haloquadratum walsbyi 23 , Haloarcula quadrata 24 , and members of the pleomorphic genus Natronrubrum 25 . FtsZ-based fission has recently been observed in the cube-shaped nematode symbiont Candidatus Thiosymbion cuboideus 26 and additional rectangular cells believed to be bacterial or archaeal have been discovered in high salinity environments but not taxonomically identified 27 . Among eukaryotic microorganisms, diatoms can have a rectangular appearance when visualized in two dimensions, although these cells are cylindrical rather than rectangular prisms 28 .…”