Understanding the mechanisms of host-pathogen interaction can provide crucial information for successfully manipulating their relationships. Because of its genetic background and practical advantages over vertebrate model systems, the nematode Caenorhabditis elegans model has become an attractive host for studying microbial pathogenesis. Here we report a "Trojan horse" mechanism of bacterial pathogenesis against nematodes. We show that the bacterium Bacillus nematocida B16 lures nematodes by emitting potent volatile organic compounds that are much more attractive to worms than those from ordinary dietary bacteria. Seventeen B. nematocidaattractant volatile organic compounds are identified, and seven are individually confirmed to lure nematodes. Once the bacteria enter the intestine of nematodes, they secrete two proteases with broad substrate ranges but preferentially target essential intestinal proteins, leading to nematode death. This Trojan horse pattern of bacterium-nematode interaction enriches our understanding of microbial pathogenesis.Bacillus nematocida | Caenorhabditis elegans | chemotaxis | pathogen-host interaction | virulence protease M ost model organisms, such as the yeast Saccharomyces cerevisiae, the slime mold Dictyostelium discoideum, the mouseear cress plant Arabidopsis thaliana, the common fruit fly Drosophila melanogaster, and the nematode Caenorhabditis elegans, can be infected by microbes, including certain human-pathogenic bacteria (1). For several reasons, C. elegans is an attractive model organism to study host-pathogen interactions: It has simple growth requirements, a short generation time, a well-defined developmental process with invariant cell lineage sorting, a fully sequenced genome, and a suite of well-established genetic tools (2). Using C. elegans as a model, scientists in the last few years have identified a diversity of physical, chemical, and biochemical features involved in microbial pathogenesis (3). For example, Brevibacillus laterosporus secretes extracellular proteases that damage nematode cuticle, and Bacillus thuringiensis produces toxic crystal proteins that disrupt host cellular functions (4, 5). The common humanpathogenic bacterium Pseudomonas aeruginosa kills C. elegans with quorum-sensing controlled-virulence factors (6) and cyanide (7). Several other human pathogens such as the Gram-negative bacteria Burkholderia pseudomallei and Serratia marcescens and the Gram-positive bacteria Enterococcus faecalis, Streptococcus pyogenes, and Staphylococcus aureus also are reported to have nematoxic activities via a neuromuscular endotoxin, a cytolysin, two extracellular proteases (gelatinase and serine protease), and several other toxins (8-12). In S. aureus, several virulence determinants known to be important in mammalian pathogenesis, including the quorum-sensing global virulence regulatory system agr and the global virulence regulator sarA, the alternative sigma factor B, α-hemolysin, and the V8 serine protease, are all required for full pathogenicity against nematode...

An Achromobacter xylosoxidans MG1 strainisolated from the effluent treatment plant of a textile and dyeing factory from Yunnan Province in China was found capable of decolorizing the malachite green dye at a high efficacy. Strain MG1 reduced 86% malachite green at the concentration of 2,000 mg/l within 1 h, representing a greater ability for decolorizing and a higher tolerance of this compound than all previously reported bacteria. Color removal was optimal at pH 6 and 38°C. Further experimental evidences demonstrated that both cytoplasmic and extracellular biodegradation contributed to the decolorization of malachite green. Nested PCR was employed to identify the candidate genes responsible for malachite green decolorization, and we identified a cytoplasmic triphenylmethane reductase gene with 100% amino acid similarity to the corresponding gene in Citrobacter sp. strain. In contrast to our expectation, the addition of metyrapone had little effect on the cytoplasmic biodegradation, suggesting that cytochrome P450 was not involved in the high-performance reduction. The extracellular biodegradation was likely attributable to the secretion of extracellular proteases and some heat-resistant compounds.

Two novel thermophilic, spore-forming bacterial strains, T-11T and E-112T, were isolated from hot springs in Tengchong and Eryuan counties of Yunnan province in south-west China. The strains were Gram-stain-positive rods, occurring singly or in chains. Growth of strain T-11T was observed between 30 and 75 °C (optimum 50 °C) and at pH 7–11 (optimum pH 8.5), while the temperature range for strain E-112T was 35–70 °C (optimum 55 °C) and the pH range was 7.0–11.0 (optimum pH 8.0). The DNA G+C contents of strains T-11T and E-112T were 41.1 and 42.6 mol%, respectively. On the basis of 16S rRNA gene sequence similarity, the two strains were shown to be related most closely to Anoxybacillus species. The chemotaxonomic characteristics [predominant isoprenoid quinone menaquinone 7 (MK-7); major fatty acids iso-C15 : 0 and iso-C17 : 0] also supported the affiliation of strains T-11T and E-112T to the genus Anoxybacillus. The results of DNA–DNA hybridization and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strains T-11T and E-112T from Anoxybacillus species with validly published names. Strains T-11T and E-112T therefore represent two novel species, for which the names Anoxybacillus tengchongensis sp. nov. (type strain T-11T =CCTCC AB209237T =KCTC 13721T) and Anoxybacillus eryuanensis sp. nov. (type strain E-112T =CCTCC AB209236T =KCTC 13720T) are proposed.

The geothermal sites near neutral and alkalescent thermal springs in Tengchong Rehai National Park were examined through cultivation-dependent approach to determine the diversity of thermophilic fungi in these environments. Here, we collected soils samples in this area, plated on agar media conducive for fungal growth, obtained pure cultures, and then employed the method of internal transcribed spacer (ITS) sequencing combined with morphological analysis for identification of thermophilic fungi to the species level. In total, 102 strains were isolated and identified as Rhizomucor miehei, Chaetomium sp., Talaromyces thermophilus, Talaromyces byssochlamydoides, Thermoascus aurantiacus Miehe var. levisporus, Thermomyces lanuginosus, Scytalidium thermophilum, Malbranchea flava, Myceliophthora sp. 1, Myceliophthora sp. 2, Myceliophthora sp. 3, and Coprinopsis sp. Two species, T. lanuginosus and S. thermophilum were the dominant species, representing 34.78% and 28.26% of the sample, respectively. Our results indicated a greater diversity of thermophilic fungi in neutral and alkaline geothermal sites than acidic sites around hot springs reported in previous studies. Most of our strains thrived at alkaline growth conditions.