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

Abstract

Growth and cell division in rod-shaped bacteria have been primarily studied in species that grow predominantly by peptidoglycan (PG) synthesis along the length of the cell. Rhizobiales species, however, predominantly grow by PG synthesis at a single pole. Here we characterize the dynamic localization of several Agrobacterium tumefaciens components during the cell cycle. First, the lipophilic dye FM 4-64 predominantly stains the outer membranes of old poles versus growing poles. In cells about to divide, however, both poles are equally labeled with FM 4-64, but the constriction site is not. Second, the cell-division protein FtsA alternates from unipolar foci in the shortest cells to unipolar and midcell localization in cells of intermediate length, to strictly midcell localization in the longest cells undergoing septation. Third, the cell division protein FtsZ localizes in a cell-cycle pattern similar to, but more complex than, FtsA. Finally, because PG synthesis is spatially and temporally regulated during the cell cycle, we treated cells with sublethal concentrations of carbenicillin (Cb) to assess the role of penicillin-binding proteins in growth and cell division. Cb-treated cells formed midcell circumferential bulges, suggesting that interrupted PG synthesis destabilizes the septum. Midcell bulges contained bands or foci of FtsA-GFP and FtsZ-GFP and no FM 4-64 label, as in untreated cells. There were no abnormal morphologies at the growth poles in Cb-treated cells, suggesting unipolar growth uses Cb-insensitive PG synthesis enzymes.agrobacterium cell cycle | bacterial cell growth | bacterial cell division | peptidoglycan synthesis

Loss of PodJ in Agrobacterium tumefaciens Leads to Ectopic Polar Growth, Branching, and Reduced Cell Division

“…Figure 4 and Video S4 in the supplemental material exemplify a cell displaying one growing pole and one nongrowing pole (0 to 20 min). Then, from 20 to 40 min the cell divides, and from 60 to 100 min, the two daughter cells grow from the poles created by the cell division event just as in the WT (11,12). GFP-PodJ At localized predominantly in larger foci at old poles and to smaller foci in new poles just prior to division (as these poles transition to old poles) as observed in the WT (21).…”

“…FtsA-GFP and FtsZ-GFP localize to the growth pole in addition to the Z-ring in WT A. tumefaciens (12). In the ⌬podJ At strain, FtsA-GFP localization patterns are more heterogeneous than those in WT cells.…”

“…Once the Agrobacterium cell has elongated sufficiently, cell wall synthesis machinery ceases activity at the growth pole and begins activity at the division site (5,11). New growth poles in daughter cells arise at the poles created by division (11,12). Finally, these organisms lack homologs of most of the elongase components, found in well-studied bacteria such as Escherichia coli or Caulobacter crescentus (5).…”

“…Remarkably, A. tumefaciens cell division proteins are possibly involved in polar growth, as hallmark cell division proteins such as FtsA and FtsZ localize to the growth pole during polar growth and subsequently localize to the midcell during division (5,12,13). As the cell approaches division, elongation at the growth pole stops and this pole transitions to an old pole (5,11,12). Therefore, polar growth must be negatively regulated during the switch to becoming an old pole.…”

The FtsZ-Like Protein FtsZm of Magnetospirillum gryphiswaldense Likely Interacts with Its Generic Homolog and Is Required for Biomineralization under Nitrate Deprivation

“…3C). Assuming a confined midcell localization of FtsZm before cytokinesis, we hypothesize that the protein becomes relocated from the new cell pole to midcell during the cell cycle and follows the dynamic localization of full-length FtsZ proteins in other alphaproteobacteria (36,37).…”