Dokument

Summary:
The peptidoglycan is an important structural element of the bacterial cell envelope and is involved in many cellular processes such as maintenance of cell shape, cell division as well as protection against extracellular stresses. Established model organisms like Escherichia coli or Bacillus subtilis have been studied extensively regarding peptidoglycan biosynthesis as well as degradation. The main goal of our research is to apply established knowledge and at the same time widen the understanding of peptidoglycan biogenesis in the human pathogen Vibrio parahaemolyticus. While the spatio-temporal organization of many synthetic and lytic enzymes is required during the bacterial cell cycle, this work focuses on the characterization of M23 peptidases, a class of enzymes responsible to reverse the trans-peptidation reaction that link the stem peptides of parallel glycan strands. Here we show that the V. parahaemolyticus genome encodes for seven M23 peptidases, some of which are homologues to identified factors important for cell division and shape in other organisms. However, we also find three previously uncharacterized, paralogous M23 peptidases. Through series of experiments, we identify one particular protein, VcsP, to be important for cell separation through its conserved M23 peptidase domain. Upon its deletion, cells exhibit a chaining phenotype that compromises the cell envelope, increasing its sensitivity to Polymyxin type antibiotics. We distinctly show that VcsP is the most important out of three paralogues. Interestingly, the dimorphic lifestyle of V. parahaemolyticus is unaffected in the absence of VcsP and cells are able to differentiate from swimmer to swarmer cell type. We utilized several approaches to find interaction partners and affectors of VcsP, and so far we show that vcsP is co-transcribed with vp0549, which encodes for a PilZ domain protein that binds the second messenger c-di-GMP. Together these findings have significantly increased our knowledge of M23 peptidases in V. parahaemolyticus and it will be interesting to find out more about VcsP and its effects in the future. We also raised additional questions in this study that we would like to address in future research.

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