Bacteria adapt to different environments by regulating cell division and several conditions that modulate cell division have been documented. Understanding how bacteria transduce environmental signals to control cell division is critical in understanding the global network of cell division regulation. In this article we describe a role for Bacillus subtilis YpsA, an uncharacterized protein of the SLOG superfamily of nucleotide and ligand-binding proteins, in cell division. We observed that YpsA provides protection against oxidative stress as cells lacking ypsA show increased susceptibility to hydrogen peroxide treatment. We found that the increased expression of ypsA leads to filamentation and disruption of the assembly of FtsZ, the tubulin-like essential protein that marks the sites of cell division in B. subtilis . We also showed that YpsA-mediated filamentation is linked to the growth rate. Using site-directed mutagenesis, we targeted several conserved residues and generated YpsA variants that are no longer able to inhibit cell division. Finally, we show that the role of YpsA is possibly conserved in Firmicutes, as overproduction of YpsA in Staphylococcus aureus also impairs cell division.

14Running title: Role of YpsA in Bacillus subtilis and Staphylococcus aureus 15 16 ABSTRACT 17Bacteria adapt to different environments by regulating cell division and several 18 conditions that modulate cell division have been documented. Understanding how 19 bacteria transduce environmental signals to control cell division is critical to comprehend 20 the global network of cell division regulation. In this article we describe a role for Bacillus 21 subtilis YpsA, an uncharacterized protein of the SLOG superfamily of nucleotide and 22 ligand-binding proteins, in cell division. We observed that YpsA provides protection 23 against oxidative stress as cells lacking ypsA show increased susceptibility to hydrogen 24 peroxide treatment. We found that increased expression of ypsA leads to cell division 25 inhibition due to defective assembly of FtsZ, the tubulin-like essential protein that marks 26 the sites of cell division. We showed that cell division inhibition by YpsA is linked to 27 glucose availability. We generated YpsA mutants that are no longer able to inhibit cell 28 division. Finally, we show that the role of YpsA is possibly conserved in Firmicutes, as 29 overproduction of YpsA in Staphylococcus aureus also impairs cell division. Therefore, 30we propose ypsA to be renamed as iodA for inhibitor of division. 31 32 IMPORTANCE 33Although key players of cell division in bacteria have been largely characterized, the 34 factors that regulate these division proteins are still being discovered and evidence for 35 the presence of yet-to-be discovered factors has been accumulating. How bacteria 36 sense the availability of nutrients and how that information is used to regulate cell 37 division positively or negatively is less well-understood even though some examples 38 exist in the literature. We discovered that a protein of hitherto unknown function 39 belonging to the SLOG superfamily of nucleotide/ligand-binding proteins, YpsA, 40 influences cell division in Bacillus subtilis by integrating metabolic status such as the 41 availability of glucose. We showed that YpsA is important for oxidative stress response 42 in B. subtilis. Furthermore, we provide evidence that cell division inhibition function of 43YpsA is also conserved in another Firmicute Staphylococcus aureus. This first report on 44 the role of YpsA (IodA) brings us a step closer in understanding the complete tool set 45 that bacteria have at their disposal to regulate cell division precisely to adapt to varying 46 environmental conditions. 47Cell division in bacteria is a well-orchestrated event that is achieved by the concerted 50 action of approximately a dozen different key division proteins (1). Amongst them a 51 protein central to cell division in most bacteria is the tubulin homolog, FtsZ, which marks 52 the site of cytokinesis (2, 3). In addition to standard spatial regulators of septum 53 positioning (4), factors that sense nutrient availability (5, 6), DNA damage (7-9), alternate 54 external environment (10, 11), have been shown to influence cel...