Search

Microorganisms are sensitive to heavy metal pollution as are other components of the biota. However, most studies on the interactions between microbes and heavy metals have been conducted in synthetic media or in altered (e.g., sterilized) environmental samples and usually have used only single species. Few studies have evaluated the effects of heavy metals on the activities of natural heterogeneous microbial populations, both autotrophic and heterotrophic, in terrestrial and aquatic environments. These latter studies have shown that heavy metals inhibit primary productivity, nitrogen fixation, the mineralization of carbon, nitrogen, sulfur, and phosphorus, litter decomposition, and enzyme synthesis and activity in soils, sediments, and surface waters. The potential adverse effects of heavy metals on such microbe-mediated ecologic processes need to be incorporated into the methodologies used by regulatory agencies, such as the U.S. Environmental Protection Agency, to prepare environmental risk assessments which, in turn, are used to formulate environmental criteria, such as the Water Quality Criteria, and to evaluate the safety to the environment of exposure to "new chemical substances," as mandated by the U.S. Toxic Substances Control Act of 1976. To provide appropriate data that can be assimilated into regulatory policy, it is essential that microbial ecotoxicity tests be standardized, are neither costly nor difficult to train personnel to conduct, and produce data that can be quantitated.

Studies were performed to determine the effects of bisulfite (HSO3−) and sulfite (SO32−), the anionic solubility products of sulfur dioxide (SO2), on the growth of bacteria and fungi and on the survival of a coliphage. Although differential sensitivities to these anions were noted among the test microorganisms, HSO3 was always more inhibitory than SO32−. The inhibitory effects of HSO3− and SO32− were pH dependent: The lower the pH, the greater their toxicity. Consequently, when evaluating the overall effects of pollution by SO2 and the resultant acid rain on the biosphere, attention must be focused on the anionic solubility products of SO2 and on the impact of the pH of the receiver environment on their toxicity to microbes.

The safety of the food additive butylated hydroxytoluene (BHT) for human consumption is being reevaluated by the U.S. Food and Drug Administration and by the Joint Expert Committee on Food Additives of the Food and Agriculture Organization and the World Health Organization of the United Nations. There are few studies on the effects of BHT to humans, with most of these studies just identifying the metabolic products of BHT. Studies with laboratory animals indicate that BHT may exert both detrimental and beneficial effects. For example, BHT ameliorates the toxicity and carcinogenicity of several chemical and physical agents, yet potentiates the toxicity and carcinogenicity of others. Furthermore, while BHT may exert a positive effect on life span, it exerts a negative effect on the lungs, kidneys, myocardial cells, liver metabolism of lipids, and clotting factors, and is a potential behavioral and developmental teratogen.

The current increased emissions of sulfur dioxide have necessitated the determination of the background levels of atmospheric sulfur-containing compounds, both inorganic and organic, to understand better the natural cycling of S through the biosphere and the impact of added S pollution. Although much is known about the sources, both anthropogenic and natural, about the sinks, both abiotic and biotic, and about the various atmospheric reactions of inorganic S-containing gases and atmospheric particulates, comparatively little is known about the atmospheric organic S-containing volatiles. The organic S-containing compounds as well as the inorganic S-containing gases volatilized from soil, fresh water, and marine environments are primarily of microbial origin. Microbes are biotic sources and potential sinks for many of the atmospheric S-containing gases and volatiles, and also the growth and activity of microbes in natural habitats are influenced by these gases and volatiles. The purpose of this review is to focus on (1) the possible contributions of volatized organic S-containing compounds to the cycling of S, (2) the involvement of microorganisms in both the production and removal of these volatile organics from the atmosphere, and (3) the effects of these volatile organics on microbial activities in natural environments. For comparison, some attention will be directed to the more prevalent inorganic S-containing constituents in the atmosphere.

A broad spectrum of microorganisms, including eubacteria (nonmarine and marine), actinomycetes, yeasts, and filamentous fungi, were evaluated for their sensitivities to nickel. Wide extremes in sensitivity to Ni were noted among the filamentous fungi, whereas the range of tolerance to Ni of the yeasts, eubacteria, and actinomycetes was narrower. With all microorganisms, the toxicity of Ni was potentiated as the pH was decreased to acidic levels. The mechanism(s) of how pH affects the toxicity of Ni has not been defined, although the formation of hydroxylated Ni species with differing toxicities was not involved. The enhanced toxicity of Ni at acidic levels may have implications for the toxicity of Ni in environments stressed by acid precipitation.