In H. pylori, lpxD was induced after adhesion to AGS gastric cancer cells [66]. Hence, the differential regulation of lpxD might allow L. interrogans to modify its lipid A, resulting in alteration of the physical properties of the outer membrane in response

to changes in environmental conditions. Notably, the lpxD is not arranged in an operon in Leptospira, and its differential regulation may thus represent a mechanism for eFT508 mouse varying LPS expression. Expression of genes encoding proteins predicted to be involved in the heat shock response, such as clpA (LIC12017) encoding the ATP-dependent proteolytic subunit of Clp endopeptidase, and htpG (LIC20044), encoding the molecular chaperone Hsp90, was down-regulated in response www.selleckchem.com/products/CAL-101.html to serum. The result is not surprising since our experiment did not generate a temperature shift between experimental and control samples, i.e. leptospires were incubated in serum and EMJH medium at the same temperature. The expression of these genes may be affected by signals other than temperature. However, further investigation is required to characterize stress signals

in serum that cause down-regulation of these genes. Additionally, down-regulation of genes encoding proteins predicted to be involved in oxidative stress, namely btuE (LIC13442) encoding glutathione peroxidase, tpx (LIC12765) encoding peroxiredoxin, bcp (LIC20093) encoding bacterioferritin comigratory protein, and ubiG (LIC10737) encoding the last enzyme in ubiquinone

biosynthetic pathway [67–69], was observed in serum-incubated leptospires, consistent PAK5 with an absence of oxidative stress in serum without any host phagocytic or other cells. Metabolism To survive in the bloodstream, pathogens need to adjust their metabolism in response to nutrient limitations. In our study, several leptospiral genes involved in metabolic processes were up- or down-regulated, depending on available sources of nutrients and energy in serum compared to those in EMJH medium. The gene hemO (LIC20148) encoding heme oxygenase was induced 2.47-fold in response to serum. Heme is an essential in vivo source of iron required for growth and biological processes, including electron transfer reactions of leptospires during infection [70]. Bacterial heme oxygenases are enzymes that release Fe2+ from heme by cleaving its tetrapyrrole ring in the presence of oxygen [71]. Previous studies have demonstrated that a transposon mutant in hemO of pathogenic Leptospira could not utilize hemoglobin (Hb) as the sole iron source [72]. In contrast, the growth of this mutant in EMJH medium, which is supplemented with FeSO4, was not impaired. Therefore, up-regulation of leptospiral hemO is likely to be necessary for iron acquisition during iron limitation conditions in serum. Indeed, HemO is required for disease pathogenesis in hamsters [73].