The amylase‐producing ability of the intestinal microflora in cultured specimens of ayu, carp, channel catfish, Japanese eel and tilapia was determined. Mean viable counts of aerobes and anaerobes ranged from 1·1×106 to 3·7×108 cfu g−1 and from 1·3×103 to 1·6×108 cfu g−1, respectively. Aeromonas spp. and Bacteroidaceae were predominant in four to five fish species. Of 206 strains examined, 65 (31·6%) produced ≥0·01 U amylase ml−1. The percentage of producers differed among families and genera of bacteria and fish species. While 56% of the anaerobes produced amylase, only 20% of the aerobes did. More than 50% of Aeromonas, Bacteroidaceae and Clostridium strains produced amylase efficiently while Acinetobacter, coryneforms, Enterobacteriaceae, Moraxella, Plesiomonas and Streptococcus strains did not. High amylase production (≥0·05 U ml−1) was found in 12 strains, 11 from Aeromonas and one Pseudomonas. The percentage of high amylase producers in Japanese eel was lower than the other four fish (2–30%). These results strongly suggest that the amylase produced by the intestinal microflora play an important role in the digestion of starch in freshwater fish to some extent.

The polymerase chain reaction (PCR) method for identification of Vibrio vulnificus in the marine environment was evaluated by comparing it to both the conventional and DNA-DNA hybridization methods. Of 13,325 isolates obtained from seawater and sediment samples, and oyster and goby specimens collected from the coastal waters of Tokyo Bay, Japan, only 61 isolates were identified as V. vulnificus on the basis of phenotypic characteristics and the amplification of the cytotoxin-hemolysin gene by the PCR method. All 61 isolates were further confirmed to be V. vulnificus by a DNA-DNA hybridization method and the API 20E system although they were divided into 13 groups on the basis of their API 20E profiles. These results strongly suggest that the PCR method is useful for identification of this organism.

The amylase-producing ability of intestinal bacteria in one marine crab and seven fish species was determined. Mean total viable counts ranged from 1.3 x lo5 to 1.5 x lo8 cfu g-', and Vibrionaceae were predominant in all specimens. Of 1585 strains examined, 341 (21.5%) produced 2 0 . 0 1 U amylase ml-'. Percentage of producers ( 2 0 . 0 1 U ml-') differed among genera/families. High abilities (20-05 U ml-') were found i n 1*4-3-6% of Enterobacteriaceae, Pseudomonas and Vibrionaceae strains. O n the other hand, percentage of producers varied with animal species. These results reveal that the amylase producers were widely distributed in the digestive tracts of coastal animals including crabs and fish, irrespective of their food habitats.