Host-Polarized Cell Growth in Animal Symbionts

• DOI: 10.1016/j.cub.2018.02.028
• Publication Date: 2018-03-22T15:52:36Z
• Authors: Nika Pende; Jinglan Wang; Philipp M. Weber; Jolanda Verheul; Erkin Kuru; Simon K.-M.R. Rit...; Nikolaus Leisch; Michael S. VanNie...; Yves V. Brun; Tanneke den Blaauwen; Silvia Bulgheresi
• Keywords: ELONGASOME; cell division; 570; Nematoda; SDG 14 – Leben unter Wasser; Peptidoglycan; peptidoglycan; FTSZ; ROD SHAPE; FtsZ; cell shape; Article; Bacterial Proteins; Cell Wall; FILAMENTS; cell growth; Animals; PEPTIDOGLYCAN SYNTHESIS; SEGREGATION; SDG 14 - Life Below Water; Symbiosis; 106021 Meeresbiologie; MREB CYTOSKELETON; Alphaproteobacteria; 106022 Mikrobiologie; DIVISION; WALL; symbiosis; 106021 Marine biology; 106022 Microbiology; MreB; PENICILLIN-BINDING-PROTEINS; Gammaproteobacteria

To determine the fundamentals of cell growth, we must extend cell biological studies to non-model organisms. Here, we investigated the growth modes of the only two rods known to widen instead of elongating, Candidatus Thiosymbion oneisti and Thiosymbion hypermnestrae. These bacteria are attached by one pole to the surface of their respective nematode hosts. By incubating live Ca. T. oneisti and T. hypermnestrae with a peptidoglycan metabolic probe, we observed that the insertion of new cell wall starts at the poles and proceeds inward, concomitantly with FtsZ-based membrane constriction. Remarkably, in Ca. T. hypermnestrae, the proximal, animal-attached pole grows before the distal, free pole, indicating that the peptidoglycan synthesis machinery is host oriented. Immunostaining of the symbionts with an antibody against the actin homolog MreB revealed that it was arranged medially-that is, parallel to the cell long axis-throughout the symbiont life cycle. Given that depolymerization of MreB abolished newly synthesized peptidoglycan insertion and impaired divisome assembly, we conclude that MreB function is required for symbiont widening and division. In conclusion, our data invoke a reassessment of the localization and function of the bacterial actin homolog.