Binary fission has been well studied in rod-shaped bacteria, but the mechanisms underlying cell division in spherical bacteria are poorly understood. Rod-shaped bacteria harbor regulatory proteins that place and remodel the division machinery during cytokinesis. In the spherical human pathogen Staphylococcus aureus, we found that the essential protein GpsB localizes to mid-cell during cell division and co-constricts with the division machinery. Depletion of GpsB arrested cell division and led to cell lysis, whereas overproduction of GpsB inhibited cell division and led to the formation of enlarged cells. We report that S. aureus GpsB, unlike other Firmicutes GpsB orthologs, directly interacts with the core divisome component FtsZ. GpsB bundles and organizes FtsZ filaments and also stimulates the GTPase activity of FtsZ. We propose that GpsB orchestrates the initial stabilization of the Z-ring at the onset of cell division and participates in the subsequent remodeling of the divisome during cytokinesis.

The antibiotic resistance (AR) patterns of 462 Escherichia coli isolates from wastewater, surface waters, and oysters were determined. Rates of AR and multiple-AR among isolates from surface water sites adjacent to wastewater treatment plant (WWTP) discharge sites were significantly higher (P < 0.05) than those among other isolates, whereas the rate of AR among isolates from oysters exposed to WWTP discharges was low (<10%).The aim of this study was to investigate the rates of antibiotic resistance among Escherichia coli isolates from a variety of sources, including wastewater treatment plants (WWTPs), surface waters (including those directly influenced by WWTP discharges), and oysters affected by WWTP discharges. This information will contribute to our understanding of antibiotic resistance in the aquatic environment and the potential environmental and public health risks associated with exposure to aquatic bacteria.This study was conducted on the central east coast of Australia on the Brisbane and Bremer Rivers and Cabbage Tree Creek, which are subtropical city-dominated systems with both estuarine and freshwater regions. Samples from each stage of the treatment process at five regional WWTPs (42 samples) were collected (Table 1), as well as samples from surface waters in the Brisbane River, including waters at sites adjacent to the investigated WWTPs (five sites referred to as point sources [PS]) and waters at sites distant from PS (six sites referred to as nonpoint sources [NPS]) (Fig. 1). Approximately 30 native oysters (Saccostrea commercialis) were collected at low tide from a small estuarine creek (Cabbage Tree Creek), approximately 300 m downstream from a WWTP discharge site (Fig. 1).The isolation of E. coli from WWTP and surface water samples was performed using membrane filtration (20). Oysters were washed and scrubbed in 70% ethanol (ChromAR [purity, 99.9%]; Mallinckrodt Chemicals) before shucking. The isolation of E. coli from oysters was carried out using a standard food technique (21).A total of 462 isolates were tested for sensitivity to six antibiotics by using the CLSI disk susceptibility testing method (5). The antibiotics chosen were ampicillin (10 g; Oxoid), cephalothin (30 g; Oxoid), nalidixic acid (30 g; Oxoid), sulfafurazole (300 g; Oxoid), gentamicin (10 g; Oxoid), and tetracycline (30 g; Oxoid). A one-way analysis of variance followed by a posthoc Tukey honestly significant difference means test was used to determine significant differences (P Ͻ 0.05) among sources of E. coli isolates for each antibiotic and among multiple-antibiotic-resistance (MAR) indices based on zones of inhibition. For MAR patterns, data were converted into a binary code (resistant or nonresistant) and differences (P Ͻ 0.05) among sources for each of the resistance patterns were evaluated by paired t tests for all combinations.The observed level of antibiotic resistance among all investigated isolates, 59%, was markedly lower than those demonstrated previously in similar studies, typically around 90% (11,16). It ...

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...

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