Polar growth in the Alphaproteobacterial order Rhizobiales

Abstract

Elongation of many rod-shaped bacteria occurs by peptidoglycan synthesis at discrete foci along the sidewall of the cells. However, within the Rhizobiales, there are many budding bacteria, in which new cell growth is constrained to a specific region. The phylogeny of the Rhizobiales indicates that this mode of zonal growth may be ancestral. We demonstrate that the rod-shaped bacterium Agrobacterium tumefaciens grows unidirectionally from the new pole generated after cell division and has an atypical peptidoglycan composition. Polar growth occurs under all conditions tested, including when cells are attached to a plant root and under conditions that induce virulence. Finally, we show that polar growth also occurs in the closely related bacteria Sinorhizobium meliloti , Brucella abortus , and Ochrobactrum anthropi . We find that unipolar growth is an ancestral and conserved trait among the Rhizobiales, which includes important mutualists and pathogens of plants and animals.

You are what you talk: quorum sensing induces individual morphologies and cell division modes in Dinoroseobacter shibae

“…However, in the latter strain the knockout leads to elongated cells. Polar growth has been described for representatives of Rhizobiales, Caulobacterales and Rhodobacterales and may be ancient in Alphaproteobacteria (Brown et al, 2012); the core genes of cell cycle control are conserved throughout the phylum (Brilli et al, 2010). This is the first time that the mode of cell division has been shown to be controlled by QS in Alphaproteobacteria.…”

Dynamic FtsA and FtsZ localization and outer membrane alterations during polar growth and cell division in Agrobacterium tumefaciens

“…Indeed, our bioinformatics searches revealed that Agrobacterium and related Rhizobiales species have more genes encoding LD-transpeptidases in their genome than other rod-shaped bacteria that predominantly encode DD-transpeptidases, and LD-transpeptidases are generally insensitive to β-lactam antibiotics (24). That PG biosynthesis in Agrobacterium is distinct is supported by its unique muropeptide profile (4). Also, in contrast to polar growth, midcell PG synthesis before division is significantly affected by Cb and results in striking tire-like expansions at this site.…”

“…Finally, cells expressing FtsA-GFP were pulse-labeled with Texas red-X succinimidyl ester (TRSE), which binds cell-surface proteins (4). Following short or long chases in media without TRSE, TRSE remained at the old pole, and FtsA-GFP was at the opposite end of the cell, namely the growth pole ( Fig.…”

“…First, a specific unipolar polysaccharide (UPP) is secreted from one pole and mediates attachment of cells to the substrate, and this activity is required for the formation of biofilms (3). Second, Agrobacterium (and other members of the Rhizobiales) grows by the addition of PG primarily at one end of the cell, the growth pole (4). After cell division, unipolar growth resumes in both daughter cells from the new cell poles generated at the division site.…”

“…Recent studies with another rod-shaped α-proteobacterium, Agrobacterium tumefaciens, revealed additional novel modes of bacterial growth and cell division (3,4). First, a specific unipolar polysaccharide (UPP) is secreted from one pole and mediates attachment of cells to the substrate, and this activity is required for the formation of biofilms (3).…”