Agrobacterium tumefaciens: A model system to investigate polar growth in bacteria
P. ZAMBRYSKI (1), J. Zupan (2), R. Grangeon (3), J. Anderson-Furgeson (3) (1) University of California, U.S.A.; (2) University of California, U.S.A.; (3) University of California, U.S.A.

Rod-shaped bacteria grow and maintain their shape by adding new peptidoglycan (PG) to their cell walls. Historically, studies have focused on bacteria, such as Escherichia coli that grow uniformly by interspersed insertion of new PG along their entire lengths. Recent work reveals another mechanism of growth from a single pole in several important animal pathogens. Two important bacteria that interact with plants, Agrobacterium tumefanciens and Rhizobium meliloti, also utilize unipolar growth. We utilize time-lapse and super-resolution fluorescence microscopy of A. tumefaciens to identify proteins involved in cell division, PG synthesis and pole identity. The tubulin homolog FtsZ and the actin homolog FtsA, localize and function at the mid-cell during septation in bacteria that grow by uniform sidewall growth. In contrast, A. tumefaciens FtsZAt and FtsAAt localize to the growing poles during most of the cell cycle and then accumulate at the mid-cell just prior to division. Caulobacter cresentus is a model system for studying the development of distinct polar morphologies and the factors responsible for their determination; the older stalked pole accumulates PopZCc, while the younger flagellated pole accumulates PodJCc. A. tumefaciens homologs of these proteins localize entirely differently. PopZAt localizes specifically to new growth poles, while PodJAt localizes to the non-growing old pole. Interestingly, PodJAt also localizes to the growing pole late in the cell cycle, when this pole must transition to a non-growing pole prior to cell division. The results provoke hypotheses for novel mechanisms that must be employed during bacterial polar growth.

Abstract Number: S5-3
Session Type: Special Session