Physiological State of Vibrio anguillarum, a Fish Pathogen, under Starved and Low-Osmotic Environments.

Abstract

Vibriosis caused by Vibrio anguillarum serotype J-O-1 seriously affects the freshwater fish ayu (Plecoglossus altivelis) in Lake Biwa, Japan. Survival patterns of V. anguillarum were investigated in aged lake water (ALW) supplemented with or without 0.75% NaCl. It was found that 0.1-1.0% of V. anguillarum cells maintained the ability to form colonies even after 6 weeks in 0.75% NaCl-ALW. Under the same starved conditions, MPN counts with liquid medium were 100 times higher than CFU counts. When exposed to sterilized aged lake water without NaCl, V. anguillarum entered a non-culturable state within half a day. As the mineralization activity of non-culturable cells was still 0.1-5.4% of that in the culturable phase, this physiological state can be described as "viable but non-culturable". However, all attempts to return to a culturable state including re-infection were unsuccessful. The non-culturable cells in ALW lost all pathogenicity in fish. Since a longer exposure to ALW resulted in less mineralization activity, the non-culturable state of V. anguillarum cells in freshwater seems to reflect a phase of decay leading to cell death. However, certain environmental factors such as coldness and microaerobiosis seem to help the pathogen to survive longer in freshwater without a loss of culturability.

Microbial communities in various waters used for fish larval rearing

“…Yamamoto, Hashimoto and Ezaki () also discussed Legionella pneumophila in the VBNC state and concluded that VBNC is in an intermediate stage during the transition from viability to death. In addition, it was shown that Vibrio anguillarum that entered the VBNC state due to low osmotic stress could not cause vibriosis in ayu, even when V. anguillarum cells were directly injected into the abdominal cavity of ayu (Eguchi, Fujiwara‐Nagata & Miyamoto ). Therefore, we speculate that many Vibrio species detected by the DGGE analysis in UV‐irradiated seawater and cold‐stored seawater may be UV‐damaged cells that were in an intermediate stage during the transition from viability to death.…”

Vibrio anguillarum as a fish pathogen: virulence factors, diagnosis and prevention

“…Nevertheless, V. anguillarum can also be found in freshwater environments such as Lake Biwa in Japan, where it is responsible for severe losses of ayu, one of the most important species in Japanese freshwater fisheries. Darkness, coldness, microaerobiosis and high cell density enhance survival of V. anguillarum in this environment, retaining its culturability and pathogenicity (Eguchi, Fujiwara & Miyamoto 2000; Eguchi, Fujiwara‐Nagata & Miyamoto 2003). Fujiwara‐Nagata & Eguchi (2003) suggested that the survival of this pathogen in the bottom sediments of Lake Biwa can be explained by the formation of a biofilm, a niche which is often associated with enhanced bacterial survival.…”

“…are also able to grow on TCBS and VAM (Bolinches, Romalde & Toranzo 1988; Alsina, Martinez‐Picado, Jofre & Blanch 1994). Furthermore, V. anguillarum can also be present in a viable but non‐culturable state during the winter months, resulting in false‐negative results (Eguchi et al. 2003; Oliver 2009).…”

Transcriptional regulation of the Na+-NADH:quinone oxidoreductase gene, nqr, in Vibrio�anguillarum, a fish pathogen, in the stationary phase

“…Vibrio anguillarum serotype J-O-1 strain M93 was originally isolated from diseased fish, Plecoglossus altivelis (Salmoniformes), in Lake Biwa, Japan. [18][19][20] Escherichia coli JM109 (Promega, Madison, WI, USA) was chosen as the host for plasmids. pGEM-T (Promega) was used for the cloning of polymerase chain reaction (PCR) products.…”