Abstract
Denitrified nitrogen in Lake Kizaki was estimated by analysis of dissolved nitrogen and argon. Denitrification in the anoxic layer and that in the oxic layer were confirmed. Vertical distributions of denitrifiers in L. Kizaki were estimated by MPN count method with Giltay's medium. In the period of circulation of lake water, denitrifiers were found throughout the water column, but they appeared discontinuously in the period of stagnation. One of the peaks was found in the oxic layer and the other in the anoxic layer. Forty-four strains of denitrifying bacteria were isolated from the lake in different seasons and at different depths. Taxonomical study was carried out with the isolated denitrifiers at generic levels. All the isolates were Gram-negative rods and motile with peritrichous or polar flagella. Most (34/44) of them were classified among Pseudomonas, some (4/44) among Alcaligenes-Achromobacter. The fluorescent group of Pseudomonas was distributed in rather oxic layers of the lake, while other groups of denitrifiers were found both in the oxic and the anoxic layers.
