MICROFLORA AND TETRODOTOXIN-PRODUCING BACTERIA IN A GASTROPOD, NIOTHACLATHRATA

Shellfish (Niotha clathrata) were collected in both July and November from three locations in Taiwan (Pingtung, Kaohsiung and Chiai Prefectu re) and assayed for anatomical distribution of tetrodotoxin (TTX) and aerobic heterotrophic bacteria. Pingtung specimens showed higher toxic ity than those from Kaohsiung and Chiai, and did not show much seasona l variation. At each site, the total aerobic bacterial counts in Novem ber samples were higher than in July. The predominant genera were Vibr io, Pseudomonas, Pasteurella, Aeromonas and Plesiomonas. Vibrio compri sed more than 35% of the genera, with V. alginolyticus as the major sp ecies. The viable counts of Vibrio species were higher in November tha n in July. However, the results did not suggest any relationship betwe en the total count or viable count and the toxicity of the shellfish. HPLC, UV and gas chromatographic-mass spectrometric analyses demonstra ted that some of the bacteria isolated, such as V. alginolyticus, V, p arahaemolyticus, Pseudomonas spp., Plesiomonas sp. and Aeromonas sp., produced TTX and/or related substances.