FtsA protein overexpression induces cell morphology changes and growth defects in Streptococcus pneumoniae.

OLIVERO, NADIA; NICOLAS REINOSO; CORTES P; HERNANDEZ MORFA, MIRELYS; ECHENIQUE J

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Congreso; Reunión Anual de la Sociedad Argentina de Microbiologia General; 2020

Sociedad Argentina de Microbiologia General

Bacterial cell division must be precisely regulated and orchestrated with other key cell cycle processes, such as cell elongation, DNA replication, and chromosome segregation, to ensure that each daughter cell is of sufficient size and contains a complete genome. In most bacteria, the cell division mechanism is initiated by the tubulin homolog FtsZ, which polymerizes in the middle of the dividing cells to form a filamentous ring. This ring is tethered to the cell membrane through FtsA, which forms actin-like protofilaments and it is also required to recruit several proteins that constitute a controlled divisome machine for septal peptidoglycan biosynthesis that leads to cell division. It also has been demonstrated that a proper ratio FtsZ/FtsA is needed for the cell division to occur in Escherichia coli. Here we used an IPTG inducible system to show that, in contrast with what happened with FtsZ, slight variations in FtsA expression induce morphological changes and cell growth defects, leading to heterogeneous cell shape and size with decreased cell growth rate, compared with wild type S. pneumoniae strain D39V. These results might indicate that in S. pneumoniae its more important to maintain FtsA levels than a fixed FtsZ/FtsA ratio. Using GFP-Trap technologies, we performed a pull-down assay to determine the interactome of FtsA. Interestingly, we found an enrichment (> -fold change) for several proteins involved in cell division and cell wall metabolism. The main hit was PBP2x, a penicillin-binding protein involved in septal peptidoglycan synthesis, which seems to confirm the role of FtsA in septal closure during cell division. Altogether these results indicate that FtsA is a key protein not only during the early cell cycle but also the latest steps of septal closure in Streptococcus pneumoniae.