Complete conversion of lactate to methane and CO₂ by triculture with a sulfate reducer, strain F-1, a hydrogen-utilizing methanogen, strain HM-1, and an acetate-utilizing methanogen, strain AM-1, was studied with sulfate-free medium under N₂ and CO₂. Strain F-1 was motile, Gram-negative and vibrio-shaped cells which utilized H₂, lactate and ethanol as electron donors. Strain F-1 were hybridized with the oligodeoxynucleotide probe complementary to specific regions of mesophilic Gram-negative sulfate-reducing bacteria (SRB probe). The G+C content of the DNA was 63.2mol%. Strain F-1 was tentatively classified into Desulfovibrio vulgaris. Strain F-1 was unable to degrade lactate in the sulfate-free medium under N₂ and CO₂. However, it degraded lactate in the dual culture with strain HM-1 in sulfate-free medium. Lactate was completely converted to methane and carbon dioxide by triculture with strain F-1, strain HM-1 and strain AM-1 which was a filamentous acetateutilizing methanogen. The triculture formed flocs and grew well on the bottom of culture flasks. Acetate accumulated in the dual culture was used concurrently with its production in the triculture. Acetate conversion to methane by strain AM-1 was not inhibited by hydrogen. Lactate was converted to methane and CO₂ stoichiometrically by the triculture in a sulfate-free minimal medium. The 16S rRNA-targeted oligodeoxynucleotide fluorescent probe in situ hybridization method was used for identification and enumeration of strain F-1 in the microbial triculture ecosystem. A large number of strain F-1 cells hybridized with the SRB probe were observed while lactate was consumed at the early stage of incubation.

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Microbial biomass in the soils of burned and unburned Japanese red pine forests in the Setouchi District, Western Japan was determined by a slightly modified chloroform fumigation-incubation method. Averages±standard deviations of microbial biomass carbon (C) of 36 unit samples in the 0-5cm soil layers at burned sites located in Ato and Nenoura were 307±206 and 789±274mg kg^-1 dry soil, respectively, and that at an unburned site at Ato was 408±213 mg kg^-1 dry soil. Soil microbial biomass C at the burned sites were approximately the same or slightly higher than at the unburned site. In contrast with soil microbial biomass, the above-ground plant biomass at the burned sites was about one-fifth or one-sixth of that at the unburned site. Microbial biomass C in the FH layer at the unburned site at Ato was 13.38±6.13g kg^-1 dry soil. No significant fluctuations of microbial biomass were observed through 1 year in the 0-5cm soil layers at either the burned and unburned sites, nor in the FH layer at the unburned site. The ratios of microbial biomass C to total C in the soils at the burned sites were 3.2-3.3%, significantly higher than those at the unburned site (2.1%). Significant correlations were observed between microbial biomass C and some soil characteristics, such as contents of total C, total nitrogen (N) and water, in both burned and unburned soils.

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The characteristics of three oligotrophic bacteria (Aeromonas sp. Y26, Aeromonas sp. Z06, and Chromobacterium sp. Y95) isolated from soil were studied and compared with those of the eutrophic bacteria, Escherichia coli and Bacillus subtilis. The K_m values of the three oligotrophic bacteria for D-glucose and L-leucine were 0.3-1.8 and 1.5-7.8μM, respectively, while those of E. coli were 1.6μM for D-glucose and 0.6μM for L-leucine. There were no significant differences of uptake kinetics between the three oligotrophic bacteria and E. coli. The oligotrophic bacteria grew in 10⁴-fold dilution of nutrient broth (NB/10⁴) with doubling times of 1.5 to 3 days and reached final yields of 5.2 to 8.6×10⁶ colony-forming units (CFU) per ml. During exponential growth in NB/10⁴, the oligotrophic bacteria maintained a high level of adenylate energy charge. The viability of the oligotrophic bacteria when they were incubated in 10mM sodium phosphate buffer (pH 7.0) decreased exponentially from 5 to 15 days of culture. However, after 60 days of culture in ultra pure water, 8-26% of the oligotrophic cells were viable.

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この概説は Trygve Braarud (1903-1985) の業績を要約したものであり、第5回有毒海産植物プランクトンに関する国際会議は彼の栄誉に対して捧げられた。彼の鞭毛藻類とそのブルームに関する科学的業績、彼の種生態学ならびに生態学的植物プランクトン研究ならびに彼の科学者としての経歴での種々の先駆的業績に焦点が当てられている。

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