[Seminar] Pneumococcal cell biology in a new light

Seminar

Title: Pneumococcal cell biology in a new light

Speaker: Katrin Beilharz

Affiliation: Molecular Genetics Department, University of Groningen

Host: Mariana Pinho, Bacterial Cell Biology Lab
 

Abstract:

Single cell techniques to study bacterial cell biology were mainly developed for model organism such as Escherichia coli, Bacillus subtilis and Caulobacter crescentus. For a long time the lack of molecular tools for Streptococcus pneumoniae limited the possibilities to study its cell biology in living cells. In order to perform single cell studies, green and red fluorescent proteins were benchmarked and a protocol to perform (fluorescent) time-lapse microscopy was optimized.

How pneumococcal cell-wall synthesis is coordinated during growth and division to achieve its characteristic oval shape is poorly understood. The conserved eukaryotic-type serine/threonine kinase of S. pneumoniae, StkP, was previously reported to phosphorylate the cell division protein DivIVA. Using “new” molecular tools, we show that GFP-StkP and its cognate phosphatase, GFP-PhpP, both localize to the division site. Further experiments suggest that the localization of StkP depends on its extracellular PASTA domains that likely sense uncrosslinked peptidoglycan since StkP and PhpP delocalize in the presence of antibiotics that target the latest stages of cell wall biosynthesis, and in non-dividing cells. With fluorescent time-lapse microscopy we investigated StkP’s recruitment to midcell relative to other essential cell division proteins FtsA and DivIVA. The stkP mutant phenotype is perturbed in cell wall synthesis and displays elongated morphologies with multiple, often unconstricted, FtsA and DivIVA rings. Overall, our results indicate that StkP signals information about the cell wall status to key cell division proteins and in this way acts as a regulator of cell division.