Unlike eukaryotes, which evolve principally through the modification of existing genetic information, bacteria have obtained a significant proportion of their genetic diversity through the acquisition of sequences from distantly related organisms. Horizontal gene transfer produces extremely dynamic genomes in which substantial amounts of DNA are introduced into and deleted from the chromosome. These lateral transfers have effectively changed the ecological and pathogenic character of bacterial species.

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Lateral gene transfer and the nature of bacterial innovation

Antibiotics in the aquatic environment - A review - Part II

Denitrification is a distinct means of energy conservation, making use of N oxides as terminal electron acceptors for cellular bioenergetics under anaerobic, microaerophilic, and occasionally aerobic conditions. The process is an essential branch of the global N cycle, reversing dinitrogen fixation, and is associated with chemolithotrophic, phototrophic, diazotrophic, or organotrophic metabolism but generally not with obligately anaerobic life. Discovered more than a century ago and believed to be exclusively a bacterial trait, denitrification has now been found in halophilic and hyperthermophilic archaea and in the mitochondria of fungi, raising evolutionarily intriguing vistas. Important advances in the biochemical characterization of denitrification and the underlying genetics have been achieved with Pseudomonas stutzeri, Pseudomonas aeruginosa, Paracoccus denitrificans, Ralstonia eutropha, and Rhodobacter sphaeroides. Pseudomonads represent one of the largest assemblies of the denitrifying bacteria within a single genus, favoring their use as model organisms. Around 50 genes are required within a single bacterium to encode the core structures of the denitrification apparatus. Much of the denitrification process of gram-negative bacteria has been found confined to the periplasm, whereas the topology and enzymology of the gram-positive bacteria are less well established. The activation and enzymatic transformation of N oxides is based on the redox chemistry of Fe, Cu, and Mo. Biochemical breakthroughs have included the X-ray structures of the two types of respiratory nitrite reductases and the isolation of the novel enzymes nitric oxide reductase and nitrous oxide reductase, as well as their structural characterization by indirect spectroscopic means. This revealed unexpected relationships among denitrification enzymes and respiratory oxygen reductases. Denitrification is intimately related to fundamental cellular processes that include primary and secondary transport, protein translocation, cytochrome c biogenesis, anaerobic gene regulation, metalloprotein assembly, and the biosynthesis of the cofactors molybdopterin and heme D1. An important class of regulators for the anaerobic expression of the denitrification apparatus are transcription factors of the greater FNR family. Nitrate and nitric oxide, in addition to being respiratory substrates, have been identified as signaling molecules for the induction of distinct N oxide-metabolizing enzymes.

/pdf/cell-biology-and-molecular-basis-of-denitrification-red4l5iffz.pdf

Cell biology and molecular basis of denitrification.

Phosphate solubilizing bacteria and their role in plant growth promotion

The ways in which plant growth promoting rhizobacteria facilitate the growth of plants are considered and discussed. Both indirect and direct mechanisms of plant growth promotion are dealt with. Th...

The enhancement of plant growth by free-living bacteria

Green roofs; building energy savings and the potential for retrofit

Genetic exchange between bacteria in the environment.

Performance and costs of power plants with capture and storage of CO2

Bacteria associated with the plant rhizosphere may have beneficial effects on plant growth by providing nutrients and growth factors, or by producing antibiotics and siderophores, which antagonize phytopathogenic fungi and bacteria. There is considerable experimental support for the idea that plant growth promoting bacteria may be used as bio–fertilizers or biological disease control agents to increase agricultural yields. Recent advances in our understanding of the molecular biology of the systems responsible for plant growth stimulation are opening the way to strain improvement by genetic engineering.

John Davison

Papers

Green roofs; building energy savings and the potential for retrofit

Genetic exchange between bacteria in the environment.

Performance and costs of power plants with capture and storage of CO2

Plant Beneficial Bacteria

Vectors with restriction site banks V. pJRD215, a wide-host-range cosmid vector with multiple cloning sites