Enterotoxigenic Escherichia coli CS6 gene products and their roles in CS6 structural protein assembly and cellular adherence

Enterotoxigenic Escherichia coli (ETEC) produces a variety of colonization factors necessary for attachment to the host cell, among which CS6 is one of the most prevalent in ETEC isolates from developing countries. The CS6 operon is composed of 4 genes, cssA, cssB, cssC, and cssD. The molecular mechanism of CS6 assembly and cell surface presentation, and the contribution of each protein to the attachment of the bacterium to intestinal cells remain unclear. In the present study, a series of css gene-deletion mutants of the CS6 operon were constructed in the ETEC genetic background, and their effect on adhesion to host cells and CS6 assembly was studied. Each subunit deletion resulted in a reduction in the adhesion to intestinal cells to the same level of laboratory E. coli strains, and this effect was restored by complementary plasmids, suggesting that the 4 proteins are necessary for CS6 expression. Bacterial cell fractionation and western blotting of the mutant strains suggested that the formation of a CssA–CssB–CssC complex is necessary for recognition by CssD and transport of CssA–CssB to the outer membrane as a colonization factor

Isolation of viable but nonculturable Vibrio cholerae O1 from environmental water samples in Kolkata, India, in a culturable state

Previously, we reported that viable but nonculturable (VBNC) Vibrio cholerae was converted into a culturable state by coculture with several eukaryotic cell lines including HT-29 cells. In this study, we found that a factor converting VBNC V. cholerae into a culturable state (FCVC) existed in cell extracts of eukaryotic cells. FCVC was nondialyzable, proteinase K-sensitive, and stable to heating at <60°C for 5 min. We prepared thiosulfate citrate bile salts sucrose (TCBS) plates with FCVC (F-TCBS plates). After confirming that VBNC V. cholerae O1 and O139 formed typical yellow colonies on F-TCBS plates, we tried to isolate cholera toxin gene-positive VBNC V. cholerae from environmental water samples collected in urban slum areas of Kolkata, India and succeeded in isolating V. cholerae O1 El Tor variant strains harboring a gene for the cholera toxin. The possible importance of VBNC V. cholerae O1 as a source of cholera outbreaks is discussed

Endangered island endemic plants have vulnerable genomes

絶滅危惧植物にのみ見られるゲノムの脆弱性を発見. 京都大学プレスリリース. 2019-07-05.Loss of genetic diversity is known to decrease the fitness of species and is a critical factor that increases extinction risk. However, there is little evidence for higher vulnerability and extinction risk in endangered species based on genomic differences between endangered and non-endangered species. This is true even in the case of functional loci, which are more likely to relate to the fitness of species than neutral loci. Here, we compared the genome-wide genetic diversity, proportion of duplicated genes (PD), and accumulation of deleterious variations of endangered island endemic (EIE) plants from four genera with those of their non-endangered (NE) widespread congeners. We focused on exhaustive sequences of expressed genes obtained by RNA sequencing. Most EIE species exhibited significantly lower genetic diversity and PD than NE species. Additionally, all endangered species accumulated deleterious variations. Our findings provide new insights into the genomic traits of EIE species

Genome Analysis of a Novel Shiga Toxin 1 (Stx1)-Converting Phage Which Is Closely Related to Stx2-Converting Phages but Not to Other Stx1-Converting Phages

Two Stx-converting phages, designated Stx1φ and Stx2φ-II, were isolated from an Escherichia coli O157:H7 strain, Morioka V526, and their entire nucleotide sequences were determined. The genomes of both phages were similar except for the stx gene-flanking regions. Comparing these phages to other known Stx-converting phages, we concluded that Stx1φ is a novel Stx1-converting phage closely related to Stx2-converting phages so far reported