Chromosome Segregation Drives Division Site Selection in Streptococcus pneumoniae

Proc Natl Acad Sci U S A. 2017 Jul 18;114(29):E5959-E5968. doi: 10.1073/pnas.1620608114. Epub 2017 Jul 3.

Abstract

Accurate spatial and temporal positioning of the tubulin-like protein FtsZ is key for proper bacterial cell division. Streptococcus pneumoniae (pneumococcus) is an oval-shaped, symmetrically dividing opportunistic human pathogen lacking the canonical systems for division site control (nucleoid occlusion and the Min-system). Recently, the early division protein MapZ was identified and implicated in pneumococcal division site selection. We show that MapZ is important for proper division plane selection; thus, the question remains as to what drives pneumococcal division site selection. By mapping the cell cycle in detail, we show that directly after replication both chromosomal origin regions localize to the future cell division sites, before FtsZ. Interestingly, Z-ring formation occurs coincidently with initiation of DNA replication. Perturbing the longitudinal chromosomal organization by mutating the condensin SMC, by CRISPR/Cas9-mediated chromosome cutting, or by poisoning DNA decatenation resulted in mistiming of MapZ and FtsZ positioning and subsequent cell elongation. Together, we demonstrate an intimate relationship between DNA replication, chromosome segregation, and division site selection in the pneumococcus, providing a simple way to ensure equally sized daughter cells.

Keywords: FtsZ; SMC; Streptococcus pneumoniae; cell division; chromosome organization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • CRISPR-Cas Systems
  • Cell Division
  • Chromosome Segregation*
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism
  • DNA Replication
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Origin Recognition Complex
  • Streptococcus pneumoniae / cytology*
  • Streptococcus pneumoniae / genetics*

Substances

  • Bacterial Proteins
  • Cytoskeletal Proteins
  • DnaX protein, Bacteria
  • FtsZ protein, Bacteria
  • OriC chromosomal replication origin
  • Origin Recognition Complex
  • Green Fluorescent Proteins
  • DNA Polymerase III