The quinone profiles of microbial biomass samples from wastewater and natural aquatic environments were studied. A soil sample was also analyzed for comparison. Attempts were made to perform numerical analyses on these profiles by using three parameters, the microbial divergence index (MD_q), the bioenergetic divergence index (BD_q), and the dissimilarity index (D), and the algorithm of the neighbor-joining method was used to make clustering trees based on D value matrix data. For these purposes, a new personal computer program named “BioCLUST” was developed. The neighbor-joining dendrograms were useful for the grouping of different microbial communities based on D value matrix data. Also, the communities could be classified effectively by plotting MD_q data against BD_q values. The numerical analysis indicated that sewage activated sludges formed a tight cluster independent of the location of plants and scale of reactors. This was also the case for influent raw sewage. Sewage microbial mats and river water were located in a group with the raw sewage cluster as the sister group. The soil and lake showed their respective independent lines. The use of our new program should facilitate microbial community analyses based on quinone patterns.

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Flow cytometry with a fluorescent antibody technique was applied to detect Escherichia coli O157: H7. Samples from the Neya River in Osaka Prefecture, Japan, were analyzed by flow cytometry to determine the number of E. coli O157: H7 in river water. The numbers of E. coli O157: H7 cells in the river water samples ranged from 5×10³ cells/ml to 6×10⁴ cells/ml. These antibody-positive cells grew during cultivation in modified EC medium. These results indicate that viable E. coli O157: H7 occurs in river water.

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It has been observed that the ciliate Euplotes grows significantly in mass cultures of the rotifer Brachionus plicatilis when the cultures deteriorate. To reveal the growth factors of Euplotes sp., we carried out culture experiments with individually inoculated Euplotes sp. by using five different microbes preferred by the rotifer for food, and observed the intracellular contents of the ciliate by microscopy. Euplotes sp. showed high growth rates (μ_max; 1.0∼2.0) on the food microbes including the inactive microalgae, Nannochloropsis oculata. However, active cells of N. oculata did not promote the growth of Euplotes sp., but significantly suppressed it compared with the control experiment of seawater alone. Furthermore, the active alga was never observed within the cells of Euplotes sp. These findings suggest that Euplotes sp. competes for dietal microbes preferred by B. plicatilis except for active N. oculata, and that active N. oculata is an effective food for preventing the proliferation of contaminated Euplotes sp. in a stable culture of the rotifer.

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It is expected that biotechnology plays a central role in making and keeping the environment clean. Most biological agents used for this purpose are microorganisms. A variety of cellular functions of microorganisms are potentially applicable to pollution prevention. These include dissimilatory oxidation and reduction of inorganic compounds, photosynthesis, co-metabolism of xenobiotics, biopolymer formation, and enzymatic transformation of heavy metals. The potential for using biological agents will be far greater if their abilities are enhanced by increasing the dosage of key genes and modifying their genetic regulation. The present review describes current efforts directed towards the genetic improvement of bacterial abilities to remove phosphorus and nitrogen compounds that are priority targets for controlling the eutrophication in natural bodies of water.

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Recently many species of algicidal microorganisms including viruses, bacteria, amoeba etc. have been detected in and after the peak of the harmful algal blooms such as dinoflagellates, raphidophytes and diatoms. These microorganisms are divided into two major types: gliding bacteria and amoeba which directly attack host algal cells after cell-to-cell attachment, and eubacteria which kill or lyse these algae through toxic substances excreted by these bacteria. The former are Cytophaga, Saprospira as gliding bacteria and Labyrinthula, while the latter are Flavobacterium, Alteromonas, Vibrio and others. Some algicidal substances have been isolated and purified, but are not yet identified. To investigate the behavior of algicidal bacteria during algal bloom, the RFLP analysis of 16S rDNA was conducted, and 4 of 17 RFLP types usually comprised the major flora in the disintegration of Heterosigma akashiwo red tide. Use of RFLP patterns and DNA probes of 16S rDNA and monoclonal antibodies as an ecological tool for ecological research and prevention of harmful algal blooms is being studied.

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To develop a practical countermeasure for eliminating harmful algal blooms (HABs), microbiological algicidity has recently been highlighted. In 1996, a virus (HaV) specifically infectious to a representative harmful bloom causing microalga, Heterosigma akashiwo, was isolated from the natural seawater. The virus has at least 4 characteristics required for biological agents to prevent H. akashiwo blooms in the natural environment: (1) HaV was isolated from “natural seawater” and experienced no artificial operation for its DNA, (2) HaV attacks H. akashiwo quite specifically, (3) HaV reproduces itself only by infecting to the host, H. akashiwo, (4) production of a small amount of HaV at a moderate price has been succeeded.

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Three ways of the transformation and degradation of dimethyl sulfide (DMS) by marine microorganisms or by their products are reviewed. DMS is transformed to methyl mercaptan and formaldehyde under oxic conditions by some strains of sulfur oxidizing bacteria and methylotrophs. DMS is transformed to dimethyl sulfoxide (DMSO) under oxic conditions by the bacterium which utilizes DMS as a sulfur source, ammonia oxidizers, methanotrophs, and photosensitizers produced by marine algae. DMS is transformed or degraded under anoxic conditions by some strains of methanogens and phototrophic bacteria.

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