title: Toxin production by Aeromonas sobria in natural environments: river water vs. seawater.
abstract: Aeromonas are water-borne pathogens. They are halotolerant, which means that they can survive in environments whose salt content corresponds to that of seawater (3.0% NaCl). However, the presence of Aeromonas in seawater is extremely rare compared with that in river water. In this study, we tested the ability of Aeromonas sobria to produce toxins in river water and seawater. First, we cultured A. sobria on skim milk agar plates supplemented with either river water (SARW) or seawater (SASW). The bacteria grew on both plates. A clear zone around the bacteria was generated in SARW. However, such a zone was not observed in SASW, suggesting that proteases were not generated in SASW. Subsequently, we cultured A. sobria in a nutrient broth supplemented with either river water (NRW) or with seawater (NSW), and examined the protease activity of their culture supernatants. The protease activity of the culture supernatant from NSW was extremely low compared to that from NRW. The immunoblotting analysis showed that serine protease (ASP) was not produced by the culture in NSW. By contrast, aerolysin-like hemolysin was produced in all conditions examined in this study. This indicates that the salinity of water is deeply involved in the production of ASP by A. sobria.
authors.affiliation: Laboratory of Protein Function, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
authors.forename: Rasel
authors.initials: R
authors.lastname: Khan
authors.forename: Eizo
authors.initials: E
authors.lastname: Takahashi
authors.forename: Hironori
authors.initials: H
authors.lastname: Nakura
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ansaruzzaman
authors.forename: Sukalyani
authors.initials: S
authors.lastname: Banik
authors.forename: Thandavarayan
authors.initials: T
authors.lastname: Ramamurthy
authors.forename: Keinosuke
authors.initials: K
authors.lastname: Okamoto
mesh_terms: D000333:Aeromonas / Q000254:growth & development* / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D003470:Culture Media; D004782:Environmental Health; D005098:Exotoxins / Q000378:metabolism; D006460:Hemolysin Proteins / Q000378:metabolism; D006461:Hemolysis; D008828:Microbiological Techniques; D010447:Peptide Hydrolases / Q000378:metabolism; D045483:Rivers / Q000382:microbiology*; D054712:Salinity; D012623:Seawater / Q000382:microbiology*
chemical_list: D001427:Bacterial Toxins; D003470:Culture Media; D005098:Exotoxins; D006460:Hemolysin Proteins; D010447:Peptide Hydrolases