Transition from aerobic to anaerobic respiration and fermentation in SD1 bacterial cells in vivo The pathogenic S. dysenteriae is a facultative anaerobe which can switch to an anaerobic energy metabolism

when C59 molecular weight starved of oxygen in the host large intestine. Proteins involved in energy metabolism formed the largest category of abundance-changed proteins under both in vitro and in vivo conditions (Figure 5), indicative of the impact of the intestinal environment on the SD1 cell’s energy generation pathways. We have previously reported in a 2D gel-based proteomic analysis that the intestinal environment resulted in a shift from aerobic respiration to fermentation in SD1 cells (15). A more comprehensive dataset was obtained in this study and highlights the advantages of 2D-LC-MS/MS and APEX over differential 2D gel display. The former approach is not only more selleck products sensitive, as it strongly increased the number of profiled low abundance proteins, but also revealed Selleckchem Dorsomorphin marked advantages via the quantitation of hydrophobic CM and OM proteins. It was confirmed that most of the tricarboxylic

acid (TCA) cycle enzymes were strongly decreased in SD1 cells in vivo, such as GltA, IcdA, SucA, SucB, SucC, SucD, SdhA, SdhB and Mdh. The abundance changes of these and following enzymes are provided in Additional File 1, Table S1. The TCA cycle was clearly less active under anaerobic (in vivo) than aerobic/microaerophilic (in vitro) conditions. New evidence was obtained that the major enzyme complex contributing electron donors in the aerobic respiratory chain, NADH:ubiquinone dehydrogenase I, was markedly less active in vivo. Nearly all of the subunits (NuoA/B/C/E/F/G/H/I/K/L/N) were decreased in abundance in vivo. Likewise, a second major electron donor enzyme complex known to be active under aerobic conditions in E. coli, succinate dehydrogenase, featured strong Thymidylate synthase decreases in vivo (SdhA/B/C/D). The cytochrome b562

protein CybC was also strongly decreased in vivo. The question arose as to which electron donor complexes substituted for Sdh and Nuo in vivo to support anaerobic and microaerobic respiration. Surprisingly, subunits of formate dehydrogenase (FdoG/H/I) were moderately decreased in abundance in vivo, whereas Fdn was not detected at all. Fdn is purportedly a selective electron donor for anaerobic respitration http://​ecocyc.​org. FNR (fumarate and nitrate reductase regulator) and NarP, both components of the complex regulatory system of respiratory enzymes, were increased in abundance in SD1 cells in vivo. FNR also activates sRNAs that degrade mRNAs coding for proteins involved in aerobic respiration [36].