Cryo-EM structures of the pore-forming A subunit from the Yersinia entomophaga ABC toxin.

ABC toxins are pore-forming virulence factors produced by pathogenic bacteria. YenTcA is the pore-forming and membrane binding A subunit of the ABC toxin YenTc, produced by the insect pathogen Yersinia entomophaga. Here we present cryo-EM structures of YenTcA, purified from the native source. The soluble pre-pore structure, determined at an average resolution of 4.4 Å, reveals a pentameric assembly that in contrast to other characterised ABC toxins is formed by two TcA-like proteins (YenA1 and YenA2) and decorated by two endochitinases (Chi1 and Chi2). We also identify conformational changes that accompany membrane pore formation by visualising YenTcA inserted into liposomes. A clear outward rotation of the Chi1 subunits allows for access of the protruding translocation pore to the membrane. Our results highlight structural and functional diversity within the ABC toxin subfamily, explaining how different ABC toxins are capable of recognising diverse hosts.

Comparative genome analyses of the pathogenic Yersiniae based on the genome sequence of Yersinia enterocolitica strain 8081.

This chapter represents a summary of the findings from the Yersinia enterocolitica strain 8081 whole genome sequence and the associated microarray analysis. Section 1 & 2 provide an introduction to the species and an overview of the general features of the genome. Section 3 identifies important regions within the genome which highlight important differences in gene function that separate the three pathogenic Yersinias. Section 4 describes genomic loci conferring important, species-specific, metabolic and virulence traits. Section 5 details extensive microarray data to provide an overview of species-specific core Y. enterocolitica gene functions and important insights into the intra-species differences between the high, low and non-pathogenic Y. enterocolitica biotypes.

Extracellular polymeric substances production kinetics of 13 sludge isolates using wastewater sludge as raw material and its flocculation potential.

The kinetics of batch fermentation of 13 extracellular polymeric substances (EPS) producing bacterial strains (9 Bacillus, 2 Serratia and 2 Yersinia) were carried out using sterilized sludge as a raw material. The most of Bacillus (µ(max): 0.11-0.27 h⁻¹), Serratia (µ(max): 0.23-0.27 h⁻¹) and Yersinia (µ(max): 0.18-0.19 h⁻¹) strains had capability to grow and produce EPS (1.36-2.12 g/L) in the sterilized sludge. In general, EPS production was mixed growth associated for all the bacterial strains cultivated independently. Bacillus sp. 7, Serratia sp. 2 and Yersinia sp. 2 produced higher concentration (1.95-2.12 g/L) of EPS than the other remaining bacterial strains. Protein and carbohydrate contents of EPS remained constant during fermentation. Broth EPS (B-EPS) exhibited high kaolin flocculation activity (≥ 75%) in most of the cases except Bacillus sp. 1, Bacillus sp. 5 and Bacillus sp. 9, respectively. In general, high flocculation activities (FAs) (≥ 75%), were attained using 1.31-1.70 mg B-EPS/g kaolin, 0.45-0.97 mg protein/g kaolin and 0.11-0.21 mg carbohydrates/g kaolin. The study suggests that further systematic exploration is required for optimizing the process of EPS production. EPS produced in the sludge can potentially be used for different water and wastewater treatments.

Biochemical diversity of the bacterial strains and their biopolymer producing capabilities in wastewater sludge.

The biochemical characterization of 13 extracellular polymeric substances (EPS) producing bacterial strains were carried out by BIOLOG. The bacterial strains were cultured in sterilized sludge for EPS production. Flocculation and dewatering capabilities of produced EPS (broth, crude slime and capsular) were examined using kaolin suspension combined with calcium (150 mg of Ca(2+)/L of kaolin suspension). BIOLOG revealed that there were 9 Bacillus, 2 Serratia and 2 Yersinia species. Most of these bacterial strains had the capability to utilize wide spectrum of carbon and nitrogen sources. EPS concentration of more than 1g/L was produced by most of the bacterial strains. Concentration of EPS produced by different Bacillus strains was higher than that of Serratia and Yersinia. Broth EPS revealed flocculation activity more than 75% for Bacillus sp.7, Bacillus sp.4 and Bacillus sp.6, respectively. Flocculation activity higher than 75% was attained using very low concentrations of broth EPS (1.12-2.70 mg EPS/g SS).

Immobilization induces alterations in the outer membrane protein pattern of Yersinia ruckeri.

We compared the outer membrane protein (OMP) pattern of 2-day-old immobilized Yersinia ruckericells (IC) with that of early (FC24) and late (FC48) stationary-phase planktonic counterparts. Fifty-five OMPs were identified. Principal component analysis discriminated between the protein maps of FC and IC. Some OMPs involved in bacterial adaptation were accumulated by both FC48 and IC but the expression of other proteins was controlled by the sessile mode of growth.