The size distribution, number and biomass of bacteria in intertidal sediments and seawater of Ohmi Bay were investigated by the image analysis and DAPI direct count technique, in March, July and November, 1983. Bacteria with the equivalent spherical diameter between 0.5 and 0.8μm occupied 75-78% of the total populations in sediments. Mean cell volume of bacteria in sediments (0.159μm³) was about twice as large as that in seawater (0.088μm³). There was no remarkable variation in bacterial mean volumes in sediments with season, depth and locality. Bacteria in sediments ranged from 6.2 to 29.2×10⁸ cells·cm^-3 in number and from 8.0 to 40.5μgC·cm^-3 in biomass. Abundance of bacteria over the top 20cm sediments varied between 2.22 and 3.76gC·m^-2. Viable bacteria enumerated by MPN method ranged from 0.2×10⁷cm^-3 in deeper sediments to 12.9×10⁷cm^-3 in surface in July. For viable bacteria, plate counts were comparable with MPN counts in sediments. Number and biomass of bacteria in seawater were 0.66-2.72×10⁶ml^-1 and 4.81-21.05μgC·l^-1, respectively. The amounts of bacteria were three orders of magnitude larger in sediments than seawater; which suggests the quantitative importance of bacteria in intertidal sediments for microbial production and remineralization of loaded organic matter.

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Four strains of non-sulfur purple photosynthetic bacteria isolated in the Bangkok area, Thailand, grew at 40 and 45°C under photosynthetic and strict anaerobic conditions. At higher temperature of 45°C, the bacteria did not grow under sealing with liquid paraffin. On the other hand, the organisms grew at 45°C, when they were allowed to grow as mixed culture with a strict aerobic bacterium, designated as 22 TW-S, under sealing with liquid paraffin. The respiratory activities of TR-22R-B, one of the isolated photosynthetic bacteria, and 22 TW-S were examined at 40 and 45°C. The oxygen uptake activities of 22 TW-S at 40 and 45°C were about 18 and 4 times higher than those of TR-22R-B, respectively, when DL-malate was used as a substrate. The redox-potential of the culture medium which permitted the initiation of growth of TR-22R-B was found to be much lower at 45°C than at 40°C. It was assumed that 22 TW-S acted as an oxygen scavenger under sealing with liquid paraffin, and thus established favorable conditions for growth of TR-22R-B.

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Seasonal changes of the number of blue-green algae-lysing microbes have been studied in relation to that of bloom-forming blue-green algae at two stations in Southern Lake Biwa in 1985. The numbers of the lyric microbes in surface water were in a range from 10² to 10⁶PFUs/ml at Yabase station and from 10² to 10⁴PFUs/ml at Shimosakamoto station. The numbers of those in the surface layer of sediment at Yabase and Shimosakamoto stations were in a range from 10³ to 10⁶PFUs/g wet wt and from 10³ to 10⁵PFUs/g wet wt, respectively. At both stations, especially at Yabase station, the number of the lytic microbes correlated with chlorophyll a. concentration and with the cell number of Anabaena solitaria.
Because bacteria always occupied the majority in the algae-lysing microbes, 8 strains of lytic bacteria were isolated. These 8 strains and the strain of LB-1 isolated from the water at Shimosakamoto station in 1984 were identified as gliding bacteria. All of them indicated strong lytic activities against 5 strains belonging to family Nostocaceae including A. solitaria and one strain of Phormidium tenue belonging to family Oscillatoriaceae, but they were hardly or not able to lyse other blue-green algae, green algae, and bacteria tested.
These results suggest that the bloom of A. solitaria in Lake Biwa should be affected by lyric bacteria.

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The annual changes in bacterial community were studied as related to those of phytoplankton in Maizuru Bay, Japan from May 1985 to April 1986. Five phytoplankton blooms were observed through the year Dominant algal species for three blooms were diatoms, Cerataulina pelagica, Asterionella japonica and Leptocylindrus danicus, and for the other two, dinoflagellate Prorocentrum micans and Raphidophycean Chattonella marina, respectively. The analysis of the bacterial community revealed that in these blooming periods the diversity of bacterial flora decreased. In particular the bacteria of genus Vibrio were not found in the bloom of phytoplankton A positive correlation was found between abundance of free-living bacteria and chlorophyll a concentrations. The results suggest that phytoplankton in the blooming period influences the bacterial flora and the bacterial concentration is closely related to the abundance of phytoplankton.

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