Brucella abortus Choloylglycine Hydrolase Affects Cell Envelope Composition and Host Cell Internalization

Choloylglycine hydrolase (CGH, E.C. 3.5.1.24) is a conjugated bile salt hydrolase that catalyses the hydrolysis of the amide bond in conjugated bile acids. Bile salt hydrolases are expressed by gastrointestinal bacteria, and they presumably decrease the toxicity of host's conjugated bile salts. Brucella species are the causative agents of brucellosis, a disease affecting livestock and humans. CGH confers Brucella the ability to deconjugate and resist the antimicrobial action of bile salts, contributing to the establishment of a successful infection through the oral route in mice. Additionally, cgh-deletion mutant was also attenuated in intraperitoneally inoculated mice, which suggests that CGH may play a role during systemic infection other than hydrolyzing conjugated bile acids. To understand the role CGH plays in B. abortus virulence, we infected phagocytic and epithelial cells with a cgh-deletion mutant (Δcgh) and found that it is defective in the internalization process. This defect along with the increased resistance of Δcgh to the antimicrobial action of polymyxin B, prompted an analysis of the cell envelope of this mutant. Two-dimensional electrophoretic profiles of Δcgh cell envelope-associated proteins showed an altered expression of Omp2b and different members of the Omp25/31 family. These results were confirmed by Western blot analysis with monoclonal antibodies. Altogether, the results indicate that Brucella CGH not only participates in deconjugation of bile salts but also affects overall membrane composition and host cell internalization

Yersinia enterocolitica palearctica serobiotype O:3/4 - a successful group of emerging zoonotic pathogens

<p>Abstract</p> <p>Background</p> <p>High-pathogenic <it>Y. enterocolitica </it>ssp. <it>enterocolitica </it>caused several human outbreaks in Northern America. In contrast, low pathogenic <it>Y. enterocolitica </it>ssp. <it>palearctica </it>serobiotype O:3/4 is responsible for sporadic cases worldwide with asymptomatic pigs being the main source of infection. Genomes of three <it>Y. enterocolitica </it>ssp. <it>palearctica </it>serobiotype O:3/4 human isolates (including the completely sequenced Y11 German DSMZ type strain) were compared to the high-pathogenic <it>Y. enterocolitica </it>ssp. <it>enterocolitica </it>8081 O:8/1B to address the peculiarities of the O:3/4 group.</p> <p>Results</p> <p>Most high-pathogenicity-associated determinants of <it>Y. enterocolitica </it>ssp. <it>enterocolitica </it>(like the High-Pathogenicity Island, <it>yts1 </it>type 2 and <it>ysa </it>type 3 secretion systems) are absent in <it>Y. enterocolitica </it>ssp. <it>palearctica </it>serobiotype O:3/4 genomes. On the other hand they possess alternative putative virulence and fitness factors, such as a different <it>ysp </it>type 3 secretion system, an RtxA-like and insecticidal toxins, and a N-acetyl-galactosamine (GalNAc) PTS system (<it>aga</it>-operon). Horizontal acquisition of two prophages and a tRNA-Asn-associated GIYep-01 genomic island might also influence the <it>Y. enterocolitica </it>ssp. <it>palearctica </it>serobiotype O:3/4 pathoadaptation. We demonstrated recombination activity of the PhiYep-3 prophage and the GIYep-01 island and the ability of the <it>aga</it>-operon to support the growth of the <it>Y. enterocolitica </it>ssp. <it>enterocolitica </it>O:8/1B on GalNAc.</p> <p>Conclusions</p> <p><it>Y. enterocolitica </it>ssp. <it>palearctica </it>serobiotype O:3/4 experienced a shift to an alternative patchwork of virulence and fitness determinants that might play a significant role in its host pathoadaptation and successful worldwide dissemination.</p

The Remarkable Chemistry of Sulfur in Hyper-Acid Crater Lakes: A Scientific Tribute to Bokuichiro Takano and Minoru Kusakabe

This chapter is a tribute to Bokuichiro Takano and Minoru Kusakabe for their important contributions to our knowledge of sulfur chemistry and dynamics in hyper-acid crater lakes and geothermal lakes. Hyper-acid crater lakes are perched at the summit of active volcanoes and represent the uppermost manifestation of a shallow active magma-hydrothermal system. They act as traps for strongly acidic condensates formed as sulfur-rich magmatic gases rising from depth expand and cool in the main hydrothermal upflow zone. The remarkable sulfate content of hyper-acid crater lakes is sourced to disproportionation-hydrolysis of magmatic SO2 in the upper part of the hydrothermal conduit. This reaction generates a strong, temperature-dependent sulfur isotopic fractionation, which typically produces high δ34SSO4 values. In contrast, sulfate in geothermal lakes displays much lighter sulfur isotopic compositions linked to oxidation of H2S-rich hydrothermal discharges. Polythionates are ubiquitous in hyper-acid crater lakes and are usually attributed to aqueous interaction between SO2 and H2S in the lake. Fluctuations in lake polythionate concentrations have been used to infer changes in the SO2/H2S ratio of magmatic hydrothermal inputs. However, polythionates may also originate from hydrolysis of elemental sulfur. Elemental sulfur in hyper-acid crater lakes occurs primarily as a molten body at the hydrothermal vent-crater floor interface. The origin of this material is not entirely clear; several deposition reactions are compatible with the observed range of sulfur isotopic compositions. Sulfide and sulfosalt minerals commonly occur as impurities in molten sulfur from hyper-acid crater lakes. Molten sulfur is also found in some geothermal lakes. There are still plenty of research opportunities for decoding the complex cycling of sulfur between aqueous and gaseous species and elemental sulfur in hyper-acid crater lakes. In particular, efforts are needed to track intermediate sulfur species. The role that subaqueous molten sulfur plays in modulating heat and mass transfers to the overlying lake and in trapping metals transported by magmatic gases deserves further investigations