In the outbreaks of food poisoning unknown of the causes to fishes and shells in Japan, recently it is presumed that the majority of the causative agents may be the so-called pathogenic halophilic bacteria, considering as a certain group of marine origin on account of their salt requirement. But notwithstanding the active and extensive researches on their distribution in sea water and marine environment, no natural source of the organisms is completely confirmed at present. Furthermore, the route of them from sea to man and habitat in winter season are unknown if they are a sort of marine bacteria. On the other hand, the fact that the optimum growth temperature of them is higher than that of most marine bacteria, and that similar bacteria are abundunt in inshore sea water, especially in summer, indicates the possibility of contamination by them from terrestrial environment, above all river water. From this point of view, the authors tried to isolate halophilic bacteria from river water in Nagasaki city during winter and summer, and could obtain many bacteria having a halophilic property. The present paper reports the method of isolation, the biological characters of the strains isolated and their requirement of salt to grow. The results are as follows; 1) The nutrient agar medium-3% NaCl, 0.1% bile salts, lactose and BTB―regarded as useful for detecting the so-called pathogenic halophilic bacteria and the peptone water with NaCl (3% after inoculation of the samples of river_water) were employed. All incubations were performed at 37℃ for 20-24 hours. The halophilic bacteria were not isolated from the agar media mixed directly with samples of river water, but by streak plating method after incubation of the peptone water inoculated samples of river water to 3% of scdium chloride. All the isolates were lactose-negative strains and no lactose-positive strains had a halophilic property (Table 1). 2) Generally, there were many differences in biochemical characters among the strains. Of these, 15 strains (41.7%) isolated in summer were identical with the pathogenic bacteria mentioned above in the basal characters (Table 2), and except the one strain identical in the majority of the other characters (Table 3). 3) The ability to grow in the peptone water containing the various concentrations of sodium chloride was found to be remarkably different between the strains obtained in winter and in summer (Table 4). It is considered that the phenomenon resulted from the differences in nature of river water in winter and summer.

1)河水からの病原性好塩菌の汚染を想定して,長崎市内の河川を対象に冬夏の二期に分けて好塩性細菌の分離を試みたところ,多数の菌株を分離することが出来た.2)これら好塩性細菌は河水から直接は分離出来ずすべて増菌培養することによってのみ得られたが,全株とも乳糖非分解性を示し乳糖分解性株には分離方法の如何によらずすべて好塩性はなかった.3)病原性好塩菌検査要領に従う生化学的性状は,一般に各菌株の間で可成りの相違がみられ分離株が多種類に亘っていることを示しているが,このうち病原性好塩菌と基本的性状の一致するものは夏季の株に41・7%含まれていた.4)冬と夏の分離株の食塩に対する増殖態度には相当の差異がみられたが,これは分離源である河水の性状が冬と夏では異なるためと推定される.

長崎大学水産学部研究報告, v.14, pp.35-41; 1963