Host-Polarized Cell Growth in Animal Symbionts

Abstract

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.

The bacterial DNA binding protein MatP involved in linking the nucleoid terminal domain to the divisome at midcell interacts with lipid membranes

“…To determine whether MatP-mCh colocalized with the cytoplasmic membrane, we transformed MG1655::MatP-mCh with a plasmid pXL28 that expresses the integral membrane protein fusion mNeonGreen-(GGS) 2 -GlpT (20). Cells were grown to steady state and the colocalization of MatP and GlpT was determined by the colocalization of the fluorescence of both proteins using the Pearson coefficient (21) as a function of the cell division cycle ( Fig. S2A ).…”

“…Concentration of the number of MatP molecules per cell and the number of molecules MatP at midcell were determined as described (16). Calculation of the Pearson coefficient of the colocalization of MatP and GlpT was determined as described (21).…”

Juxtaposed membranes underpin cellular adhesion and display unilateral cell division of multicellular magnetotactic prokaryotes

“…4). It has been reported recently that nematode symbiont rod-shaped Gammaproteobacteria initiate division by membrane invagination only at the proximal pole that is attached to the host cuticle (Pende et al, 2018). The fission progresses by membrane invagination at the distal end and the two constriction furrows penetrate longitudinally toward the centre until there is a complete division.…”

Non-essentiality of canonical cell division genes in the planctomycete Planctopirus limnophila

“…However, recent studies on various non-model organisms have begun to reveal that some of the statements derived from model organisms do not apply to bacteria universally. A wide variety of different cell division mechanisms is bound to broaden our perspective about bacterial cell division 34,55 .…”