Identification of SepF in Streptococcus suis involving cell division.

Background: Streptococcus suis (S. suis) is a major zoonotic pathogen that infects humans and pigs. The increasing emergence and dissemination of antibiotic resistance bacteria accelerates the urgent need to develop novel drug targets. Bacterial cell divisome is attractive target. FtsZ, an essential tubulin-like protein, forms a Z-ring that executes the synthesis of the divisome. However, the exact division process of S. suis remains unknown.

Results: here, we reported a SepF homolog from S. suis that modulated the function of FtsZ. sepF disruption was not lethal and its deletion mutant (∆sepF) displayed normal growth rate. ∆sepF exhibited long chains, occasionally anuclear daughter cells. Electron microscope revealed that the lack of SepF in cells led to abnormal septum which twisted out of shape, and disturbed cell division due to an increased length-width ratio and multiple septal peptidoglycan wall in a cell compared to the wild type strain. Mechanistic studies showed that SepF interacted with FtsZ to promote the bundling of FtsZ protofilaments. Furthermore, sub-cellular localization of FtsZ-GFP in ∆sepF also confirmed the abnormal septum and cell morphology.

Conclusions: These results showed that SepF was a cell division protein in S. suis responsible for maintaining cell shape and regulating FtsZ localization.