SepF supports the recruitment of the DNA translocase SftA to the Z-ring

In many bacteria, cell division begins before the sister chromosomes are fully segregated. Specific DNA translocases ensure that the chromosome is removed from the closing septum, such as the transmembrane protein FtsK in Escherichia coli. Bacillus subtilis contains two FtsK homologues, SpoIIIE and SftA. SftA is active during vegetative growth whereas SpoIIIE is primarily active during sporulation and pumps the chromosome into the spore compartment. FtsK and SpoIIIE contain several transmembrane helices, however, SftA is assumed to be a cytoplasmic protein. It is unknown how SftA is recruited to the cell division site. Here we show that SftA is a peripheral membrane protein, containing an N-terminal amphipathic helix that reversibly anchors the protein to the cell membrane. Using a yeast two-hybrid screen we found that SftA interacts with the conserved cell division protein SepF. Based on extensive genetic analyses and previous data we propose that the septal localization of SftA depends on either SepF or the cell division protein FtsA. Since SftA seems to interfere with the activity of SepF, and since inactivation of SepF mitigates the sensitivity of a ∆sftA mutant for ciprofloxacin, we speculate that SftA might delay septum synthesis when chromosomal DNA is in the vicinity

Detection of single-stranded plasmid DNA

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Change of a catalytic reaction carried out by a DNA replication protein.

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ComE/ComE~P interplay dictates activation or extinction status of pneumococcal X-state (competence)

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RocS drives chromosome segregation and nucleoid protection in Streptococcus pneumoniae.

Chromosome segregation in bacteria is poorly understood outside some prominent model strains <sup>1-5</sup> and even less is known about how it is coordinated with other cellular processes. This is the case for the opportunistic human pathogen Streptococcus pneumoniae (the pneumococcus) <sup>6</sup> , which lacks the Min and the nucleoid occlusion systems <sup>7</sup> , and possesses only an incomplete chromosome partitioning Par(A)BS system, in which ParA is absent <sup>8</sup> . The bacterial tyrosine kinase <sup>9</sup> CpsD, which is required for capsule production, was previously found to interfere with chromosome segregation <sup>10</sup> . Here, we identify a protein of unknown function that interacts with CpsD and drives chromosome segregation. RocS (Regulator of Chromosome Segregation) is a membrane-bound protein that interacts with both DNA and the chromosome partitioning protein ParB to properly segregate the origin of replication region to new daughter cells. In addition, we show that RocS interacts with the cell division protein FtsZ and hinders cell division. Altogether, this work reveals that RocS is the cornerstone of a nucleoid protection system ensuring proper chromosome segregation and cell division in coordination with the biogenesis of the protective capsular layer