Shewanella putrefaciens, a major microbial species related to tetrodotoxin (TTX)-accumulation of puffer fish Lagocephalus lunaris

AIMS: To investigate the major micro-organisms, which were isolated from internal organs, related to tetrodotoxin (TTX)-accumulation of puffer fish Lagocephalus lunaris. METHODS AND RESULTS: Puffer fish Lagocephalus lunaris around Chang Island in the Gulf of Thailand were collected to examine TTX-accumulation and microbial load in internal organs. The nine predominant micro-organisms isolated from the internal organs were determined TTX and studied in relation to the TTX-accumulation of the puffer fish. Shewanella putrefaciens, a predominant bacterium and related to the TTX-accumulation of the puffer fish, was examined growth and TTX-production after culture in modified Zobell medium. The results revealed that the average TTX-accumulation of the puffer fish directly varied to the bacterium load periodically, year-round. Furthermore, it coincided with the growth and the TTX-production of the bacterium, which grew slowly but produced high TTX at low temperature. CONCLUSIONS: Shewanella putrefaciens was a major bacterium relating to TTX-accumulation of puffer fish L. lunaris. It resulted in high TTX-accumulation of the puffer fish at low temperatures of seawater. SIGNIFICANCE AND IMPACT OF THE STUDY: Temperature affected growth and TTX-production of S. putrefaciens that resulted in TTX accumulated in puffer fish L. lunaris.