Isolation and characterization of mesotrione-degrading Bacillus sp. from soil

International audienceDissipation kinetics of mesotrione, a new triketone herbicide, sprayed on soil from Limagne (Puy-de-Dôme, France) showed that the soil microflora were able to biotransform it. Bacteria from this soil were cultured in mineral salt solution supplemented with mesotrione as sole source of carbon for the isolation of mesotrione-degrading bacteria. The bacterial community structure of the enrichment cultures was analyzed by temporal temperature gradient gel electrophoresis (TTGE). The TTGE fingerprints revealed that mesotrione had an impact on bacterial community structure only at its highest concentrations and showed mesotrione-sensitive and mesotrione-adapted strains. Two adapted strains, identified as Bacillus sp. and Arthrobacter sp., were isolated by colony hybridization methods. Biodegradation assays showed that only the Bacillus sp. strain was able to completely and rapidly biotransform mesotrione. Among several metabolites formed, 2-amino-4-methylsulfonylbenzoic acid (AMBA) accumulated in the medium. Although sulcotrione has a chemical structure closely resembling that of mesotrione, the isolates were unable to degrade i

Pathogenic potential and virulence genotypes of intestinal and faecal isolates of porcine post-weaning enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) are frequent causes of diarrhoea in infants and in young mammals by inducing attaching effacing (AE) lesions of the intestinal epithelium. EPEC bacteria have also been implicated in cases of porcine post-weaning diarrhoea but their pathogenicity for conventional weaned pigs remains less elucidated. This present study investigates differences in pathogenic potential and virulence genotypes of intestinal and faecal isolates of EPEC from newly-weaned pigs. For this we inoculated ligated ileal loops of four weeks old weaned pigs to assess EPEC adherence to enterocytes by histology and immunohistology. Virulence gene patterns were identified by using a PCR-microarray. Intestinal EPEC isolates of sero −/intimin types O45:H11:eae-β, O49:NM:eae-β, O84:H7:eae-γ, and O123:H11:eae-β formed adherent microcolonies of EPEC with AE lesions on ileal villi more frequently than faecal isolates of O28:H28:eae-NT, O108:H9:eae-β, O145:H28:eae-γ and O157:H2:eae-β (p ≤ 0.05). The PCR-array analysis of both groups detected all together 25 virulence genes of LEE (Locus of Enterocyte Effacement), and of non-LEE pathogenicity islands, of plasmids and phages characteristic to EPEC. Intestinal isolates carried significantly more virulence genes than faecal isolates (p ≤ 0.05). Intestinal isolates possessed efa1, lpfA, and tsh genes most likely contributing to enterocyte adhesion while faecal isolates did not carry these genes (p ≤ 0.05). Overall, the ileal loop model in weaned pigs combined with virulence genotyping PCR-array indicated a greater pathogenic potential of intestinal isolates over faecal isolates of porcine post-weaning EPEC. Differing virulence genotypes of the intestinal and faecal isolates as demonstrated here suggests dynamic evolutionary events within the population of porcine EPEC. © 2017 Elsevier Lt

Cure and Curse: E. coli Heat-Stable Enterotoxin and Its Receptor Guanylyl Cyclase C

Enterotoxigenic Escherichia coli (ETEC) associated diarrhea is responsible for roughly half a million deaths per year, the majority taking place in developing countries. The main agent responsible for these diseases is the bacterial heat-stable enterotoxin STa. STa is secreted by ETEC and after secretion binds to the intestinal receptor guanylyl cyclase C (GC-C), thus triggering a signaling cascade that eventually leads to the release of electrolytes and water in the intestine. Additionally, GC-C is a specific marker for colorectal carcinoma and STa is suggested to have an inhibitory effect on intestinal carcinogenesis. To understand the conformational events involved in ligand binding to GC-C and to devise therapeutic strategies to treat both diarrheal diseases and colorectal cancer, it is paramount to obtain structural information on the receptor ligand system. Here we summarize the currently available structural data and report on physiological consequences of STa binding to GC-C in intestinal epithelia and colorectal carcinoma cells

Initial adherence of EPEC, EHEC and VTEC to host cells

Initial adherence to host cells is the first step of the infection of enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic Escherichia coli (EHEC) and verotoxigenic Escherichia coli (VTEC) strains. The importance of this step in the infection resides in the fact that (1) adherence is the first contact between bacteria and intestinal cells without which the other steps cannot occur and (2) adherence is the basis of host specificity for a lot of pathogens. This review describes the initial adhesins of the EPEC, EHEC and VTEC strains. During the last few years, several new adhesins and putative colonisation factors have been described, especially in EHEC strains. Only a few adhesins (BfpA, AF/R1, AF/R2, Ral, F18 adhesins) appear to be host and pathotype specific. The others are found in more than one species and/or pathotype (EPEC, EHEC, VTEC). Initial adherence of EPEC, EHEC and VTEC strains to host cells is probably mediated by multiple mechanisms

Contribution of defined amino acid residues to the immunogenicity of recombinant Escherichia coli heat-stable enterotoxin fusion proteins.

International audienceWe investigated whether the toxicity-associated receptor-binding domain of the non-immunogenic Escherichia coli heat-stable enterotoxin (STh) as a fusion with a carrier protein and the inclusion of an appropriate spacer are critical factors for eliciting antibody responses against the native toxin. The immunological properties of three toxic and one non-toxic fusion proteins, consisting of STh N-terminally joined to the C-terminus of the major subunit ClpG of E. coli CS31A fimbriae, were compared. In contrast to the non-toxic hybrid STh with glycine and leucine simultaneously substituted for the receptor-interacting Pro(13) and Ala(14) amino acids, the toxic chimeras responded by producing high serum levels of anti-STh antibodies in immunized animals. On the other hand, only the toxic ClpG-STh construct with the natural peptide 47KSGPESM(53) of Pro-STh as spacer stimulated STh-neutralizing responses against both native toxin and enterotoxigenic live E. coli cells. Altogether, these findings suggest a close relationship between conformational similarity to the native structure of STh and the ability to elicit specific antibody responses against STh