STUDIES ON MARINE NITRIFYING BACTERIA (NITRITE FORMERS AND NITRATE FORMERS)-III:ON THE NITRITE FORMATION OF THE MARINE NITRITE FORMERS

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We obtained two kinds of almost pure culture of the marine nitrite former (ammonia oxidizing bacteria), one (M 2) from the bottom muds of Maizuru Bay and the other (A 6) from the filter-sand of the sea-water aquarium with circulating system. The cultures included a species of heterotrophic bacteria, Vibrio adaptatus like strain, as a sole contaminant. In this paper, the effects of some of the environmental factor on the nitrite formation were examined, by using of the resting bacterial cells adhering to the sand. The results which were obtained are as follows: 1. The marine nitrifying bacteria show the maximum nitrite formation in sea water or in the solution with ca. 30‰ NaCl concentration, and the lower the salt concentration, the less the activity. This reduction of the activity seems to be caused by the decrease in the enzyme activity of the resting cells themselves rather than by the fact that the low salted solution is unsuited for their enzymatic reaction. 2. The maximum nitrite formation occurs at about 35°C, and at around pH 8.0. Most of the activity is lost above 45°C, however, the formation gradually changes within the range from pH 6.0 to pH 10.0. 3. The substrate concentration which gives the maximum nitrite formation of M 2 is ca. 30mg/l (NH4)2SO4, and somewhat lower than that of A 6.
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