Effect of zinc on bacterial flora in soil was studied. Cellular fatty acid composition was analyzed with bacteria isolated from a soil incubated with glucose (C source) and ammonium sulfate (N source) in the presence or absence (control) of zinc chloride (1, 000ppm as Zn). Isolated strains were classified by the cluster analysis based on the correlation coefficient (r) computed using their fatty acid composition. At the 0.95r level strains isolated from the control soil were separated into 8 clusters and 2 of them predominated. On the other hand, isolated strains from the soil with zinc added similarly fell into 8 clusters and 4 of them became predominant successively in the incubation. Most of the strains belonging to the clusters obtained in the soil with zinc were zinc-tolerant and had low similarity to those in the control soil.

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Distribution of members of marine Vibrionaceae, which is a typical group of marine heterotrophic bacteria, was surveyed in both an eutrophic inner bay and oligotrophic open seas, and the influence of biotic and abiotic factors on the abundance of the Vibrionaceae was analysed.
The results showed that members of Vibrionaceae are widely distributed over the whole the sampling area. In the coastal environments the vertical distribution of the Vibrionaceae followed the similar pattern as that of the general heterotrophic bacterial population that are countable by the agar plate method, and both the number of vibrios and the heterotrophic bacteria decreased fairly constantly according to the increasing depth. However, in the open seas, the rate of decrease in vibrio numbers was smaller than that of the heterotrophic bacteria, so that the proportion of vibrios to heterotrophic bacteria increased with depth.
No clear diurnal changes in the vertical distribution of Vibrionaceae and total heterotrophic bacteria was observed in the experiments in the open seas. However, at a sampling point of the South China Sea a rapid increase and following decrease in vibrio numbers of the surface seawater were observed during the two days of observation.
Statistical analysis, correlation analysis and principal component analysis of biotic and abiotic factors suggested that Vibrionaceae have different responses to environmental factors than other heterotrophic bacterial population. There were reverse correlations between the ratio of vibrios/plate counts and other indices of organic substances including other bacteria, the results indicating that the ratio will serve as an indicator of organic pollution of coastal seawater. Principal component analysis also showed the difference between vibrio numbers and other bacterial numbers. In a survey in Tokyo Bay the eigen vector of vibrio numbers in the first principal component reversely contrasted to those of other indices. Also, in the data from the open seas, the vibrio numbers, unlike total counts and plate counts, showed clear contrast with chlorophyll pigments in the 2nd principal component.

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