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In the previous oceanographic survey conducted by HORIE et al .8) it was revealed that Biotype 1 organisms of Vibrio parahaemolyticus distribute in coastal sea area. It was also noted that Biotype 1 organisms can be more frequently isolated from plankton or marine mud than from sea water sample. The present study was undertaken to investigate the occurrence of Biotype 1 or 2 organ isms in the plankton or fish inhabiting in the pelagic ocean. The survey was carried out aboard the Umitaka-maru, a research vessel of Tokyo University of Fisheries in the sea off Southern Kanto and Tokai districts late in July 1963. The location of sampling stations is shown in Fig. 1. Plankton samples were obtained at all the 13 stations , whereas young fish were caught only at 3 stations. At the station 9, particularly , several samples of sizable fish and squid could be caught using flyingfish drift net , and the gastric contents of these organ isms were tested. A selective liquid medium, 3% NaCl containing arabinose ethyl violet broth (AE medium) , as shown in Table 1, was used. In order to get higher rate of detection of Biotype 1 organ isms, ME medium, 3% NaCl containing mannitol ethyl violet broth was employed , and the said medium of pH 7.8 was used in parallel with that of pH 9 .0. No bacteria belonging to Biotype 1 could be detected from the samples collected i n the pelagic ocean, whereas Biotype 2 were found to be widely distributed in the plankton samples. Bi otype 3 bacteria was not isolated from the plankton , but detected in the samples of young fish and in the gastric contents of fish and squid. Some strains isolated from the flying fish could be classified as Biotype 2 on account of the salt resistance , positive Voges-Proskauer reaction and sucrose fermentation, however , they were differentiated from the typical organ isms of Biotype 2 by other biological features.

Species composition and growth-temperature characteristics of coliforms isolated from several types of environmental samples were investigated. It was possible to divide these isolates into eight distinct groups, six species groups and two unidentified, on the basis of their biochemical properties. The isolates included in the unidentified groups, giving IMViC reactions of --+ + and -+ -+, were tentatively termed "typical psychrotrophic coliform (TPC)" bacteria because of their ability to grow at 10. The TPC bacteria and Citrobacter freundii constituted the normal coliform flora of mountain soil and stream water samples. In contrast, Escherichia toll and Klebsiella pneumoniae were major predominant coliforms in polluted river water and sewage samples, the former being most common in human feces samples. In testing the growth response at different temperatures, the isolates of E. toll and the TPC bacteria showed relatively constant temperature preferences regardless of origin, whereas those of other coliform members gave varied results dependent upon their sources. The results provided circumstantial evidence that population densities of coliforms able to grow in EC broth at 43° and above but not in ordinary nutrient broth at 5° within 7 days of incubation in the environment are directly proportional to the degree of potential fecal contamination.The coliform bacteria are well established as indicators of hazardous fecal contamination of water and food (1, 2). Apart from Escherichia coli, a member of this group, these bacteria occur frequently in areas apparently free from obvious fecal contamination, although all coliforms were once thought of as being of fecal origin (3). Thus, the sanitary significance of coliforms not related to fecal sources has been and still is of major concern, with much interest being directed