Poster

  • P-MCB-014

Unveiling the dynamics of chromosome segregation in Rhodomicrobium vannielii DSM166

Presented in

Poster Session 2

Poster topics

Authors

Vanessa Bieberstein (Bayreuth / DE), Frank D. Müller (Bayreuth / DE)

Abstract

The segregation of bacterial chromosomes is typically controlled by the conserved tripartite ParABS system. This system orchestrates the segregation of the origin of replication early in the cell cycle, concomitantly with DNA replication and is essential for the faithful distribution of the paired chromosomes. The ParABS system comprises the ATPase ParA, the ori-proximal sequence parS, and the parS binding CTPase ParB. Upon ATP binding and dimerization, ParA is believed to interact with DNA in a non-specific manner. ParB proteins bound to parS interact with each other to form a spreading nucleoprotein complex that interacts with DNA-bound ParA dimers. This tripartite chromosome partitioning system is hypothesized to mediate the net movement of the replicated chromosomal origin to the opposite cell pole. However, research on chromosome segregation has predominantly focused on bacteria with simple rod-like or coccoid morphology. As a result, the corresponding processes in prosthecate budding bacteria are largely unknown. These bacteria must move the chromosome through a narrow hypha to reach distant progeny. Current models cannot explain this process suggesting that our understanding of chromosome segregation in bacteria is incomplete. Nonetheless, the absence of suitable model organisms impedes the study of this process. We have successfully genetically accessed Rhodomicrobium vannielii, a notable multipolar Alphaproteobacterium, known for its pleomorphic cells that reproduce through bud formation at the tips of extended hyphae. We traced the dynamic localization patterns of both ParA and ParB proteins by fluorescent labelling and fluorescence time-laps microscopy. Statistical analysis of the fluorescence signals indicates that chromosome translocation begins only after the bud has reached a certain size, suggesting the existence of an unidentified checkpoint. Furthermore, translocation occurs rapidly, indicating an active DNA transport mechanism of unknown identity.

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