Legionella pneumophila is a facultative intracellular pathogen capable of entering and growing in a variety of phagocytic cells including free-living amoebae as well as alveolar macrophages and monocytes. A genetic analysis of L. pneumophila should facilitate the identification of bacterial factors that promote the intracellular lifestyle of this organism.
Microbial activity in the sea is affected by fronts (interfaces between water masses). Stratified water on one side has greater heterotrophic activity than does mixed water on the other. Greatly enhanced activity adjacent to tidal mixing fronts is evidently the indirect result of water movements associated with the fronts.
The predatory bdellovibrios acquire all their growth requirements by preying upon other Gram-negative bacteria. They reutilize biosynthetic monomers, remanufacture the prey's lipopolysaccharide, and relocalize specific outer membrane proteins from the prey to their own outer membranes. This lifestyle occurs without loss of the biosynthetic potential for axenic growth.
The discovery of teichoic acids in the cell walls of a number of actinomycetes suggests that these polymers are widespread in the order Actinomycetales. Structural variations in the teichoic acids are described and their possible physiological functions are discussed.
Agrobacterium tumefaciens is a soil inhabitant that infects many dicotyledonous plants, causing crown gall disease. The success of Agrobacterium radiobacter K84 to control this disease in agroecosystems throughout the world has been impressive. This review describes the attributes of K84, its mechanism of control, its failures, and other alternative biocontrol agents.
The production of toxic or recalcitrant waste effluents by the chemical industry is leading to major problems of their disposal. New biotechnological approaches are now being used which will enable biological treatment of these wastes and will, in future, replace existing methods of effluent treatment.
DNA probes are useful for both identification and enumeration of specific bacteria and functional groups of bacteria in environmental samples. Because probes can detect genes, chromosomes, and plasmids, they also promise to be major sources of information about the relatedness of bacteria and groups of bacteria in the environment.
The virulent phenotype of Shigella is genetically controlled in the diverse form. Both chromosomal and extrachromosomal genetic loci that are required for the expression of the virulent phenotype have been identified. Advances in the genetics and the molecular biology of Shigella virulence are discussed.
The importance of microbial adaptation in the removal of environmental pollutants and in maintaining active microbial communities in impacted ecosystems is discussed using the biodegradation of p-nitrophenol and the volatilization of mercuric mercury as examples. A molecular mechanism of adaptation is suggested by enrichment of mercury resistance (mer) genes in some communities upon exposure to mercury.
This discussion examines various potential targets of immune attack on human immunodeficiency virus (HIV) as recognized by antibodies obtained experimentally as well as under natural conditions of infection. Various issues related to vaccine strategies are discussed in this light as are limited experimental trials of candidate vaccines carried out to date.
Streptomyces spp. are soil microorganisms that are important in decomposition of organic matter in soil. Genetic exchange among Streptomyces species is known to occur readily both on agar and in soil in the laboratory and evidence indicates that transfer of genes from released recombinant Streptomyces to native soil streptomycetes also occurs. Minimal data are available on the environmental effects of such gene transfer.
