During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism’s pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.

Bacillus thuringiensis and Its Pesticidal Crystal Proteins

Over three decades of molecular-phylogenetic studies, researchers have compiled an increasingly robust map of evolutionary diversification showing that the main diversity of life is microbial, distributed among three primary relatedness groups or domains: Archaea, Bacteria, and Eucarya. The general properties of representatives of the three domains indicate that the earliest life was based on inorganic nutrition and that photosynthesis and use of organic compounds for carbon and energy metabolism came comparatively later. The application of molecular-phylogenetic methods to study natural microbial ecosystems without the traditional requirement for cultivation has resulted in the discovery of many unexpected evolutionary lineages; members of some of these lineages are only distantly related to known organisms but are sufficiently abundant that they are likely to have impact on the chemistry of the biosphere.

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A Molecular View of Microbial Diversity and the Biosphere

A new hierarchic classification structure for the taxa between the taxonomic levels of genus and class is Proposed for the actinomycete line of descent as defined by analysis of small subunit (16S) rRNA and genes coding for this molecule (rDNA). While the traditional circumscription of a genus of the actinomycete subphylum is by and large in accord with the 16S rRNA/rDNA-based phylogenetic clustering of these organisms. most of the higher taxa proposed in the past do not take into account the phylogenetic clustering of genera. The rich chemical, morphological and physiological diversity of phylogenetically closely related genera makes the description of families and higher taxa so broad that they become meaningless for the description of the enclosed taxa. Here we present a classification system in which phylogenetically neighboring taxa at the genus level are clustered into families, suborders, orders, subclasses, and a class irrespective of those phenotypec characteristics on which the delineation of taxa has been based in the past. Rather than being based on a listing of a wide array of chemotaxonomic, morphological, and physiological properties, the delineation is based solely on 16S rDNA/rRNA sequence-based phylogenetic clustering and the presence of taxon-specific 16S rDNA RNA signature nucleotides.

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Proposal for a New Hierarchic Classification System, Actinobacteria classis nov.

Distribution of isoprenoid quinone structural types in bacteria and their taxonomic implication.

The moderately halophilic heterotrophic aerobic bacteria form a diverse group of microorganisms. The property of halophilism is widespread within the bacterial domain. Bacterial halophiles are abundant in environments such as salt lakes, saline soils, and salted food products. Most species keep their intracellular ionic concentrations at low levels while synthesizing or accumulating organic solutes to provide osmotic equilibrium of the cytoplasm with the surrounding medium. Complex mechanisms of adjustment of the intracellular environments and the properties of the cytoplasmic membrane enable rapid adaptation to changes in the salt concentration of the environment. Approaches to the study of genetic processes have recently been developed for several moderate halophiles, opening the way toward an understanding of haloadaptation at the molecular level. The new information obtained is also expected to contribute to the development of novel biotechnological uses for these organisms.

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Biology of moderately halophilic aerobic bacteria

The archaea - their history and significance, C.R. Woese list of contributors central metabolism of the archaea, M.J. Danson bioenergetics of extreme halophites, V.P. Skulachev biochemistry of methanogenesis, L. Daniels and B. Mukhopadhyay bioenergetics and transport in methanogens and related thermophilic archaea, P. Schonheit signal transduction in halobacteria, D. Oesterhelt and W. Marwan ion transport rhodopsins (bacteriorhodopsin and halorhodopsin) - structure and function, J.K. Lanyi proteins of extreme thermophiles, R. Hensel cell envelopes of archaea - structure and chemistry, O. Kandler and H. Konig membrane lipids of archaea, M. Kates the membrane-bound enzymes of the archaea, L.I. Hochstein chromosome structure, DNA topoisomerases, and DNA polymerases in archaebacteria (archaea), P. Forterre and C. Elie transcription in archaea, W. Zillig et al translation in archaea, R. Amilis et al the structure, function and evolution of archaeal ribosomes, C. Ramirez et al halobacterial genes and genomes, L.C. Schalkwyk structure and function of methanogen genes, J.R. Palmer and J.N. Reeve archaeal hyperthermophile genes, J.Z. Dalgaard and R.A. Garrett epilogue, W.F. Doolittle.

The Biochemistry of archaea (archaebacteria)

An actinomycete, isolated as a contaminant of a culture medium containing 25% NaCl, has been classified as Actinopolyspora halophila gen. et sp. nov. in the family Nocardiaceae. The morphology and biochemical characteristics of this organism distinguish it from other members of the family Nocardiaceae and other genera possessing a type IV cell wall. It requires high NaCl concentrations for growth and can grow in saturated NaCl. The lowest concentration permitting growth in liquid medium is 12%, and on solid medium, 10%. Colonies developing at lower salt concentrations contain holes resembling viral plaques. No growth occurred in a medium containing 30% KCl instead of NaCl. This organism can grow in simple media with NH4+ salts as nitrogen source and different sugars and other compounds as carbon source. Though it has a salt requirement almost as great as the extremely halophilic rods and cocci, it differs from these in containing diaminopimelic acid and in sensitivity to lysozyme; both properties suggest that it has a mucopeptide cell wall. It also contains some phospholipids common to other actinomycetes, but does not contain any phytanyl ether linked lipids characteristic of other extremely halophilic bacteria.

Isolation and characterization of Actinopolyspora halophila, gen. et sp. nov., an extremely halophilic actinomycete.

Quantitative measurements were carried out on pigmented and colorless isoprenoid compounds in several species of extremely and moderately halophilic bacteria. Phytoene was found in most extreme halophiles; it was present in high concentrations in a moderately halophilic coccus (H5) and absent from a moderately halophilic rod (A31C). Only the pigmented extreme halophiles contained β-carotene. Halobacterium cutirubrum contained substantial amounts of lycopene; this compound was present only in small amounts or missing from the other bacteria. Though lycopene is a precursor of β-carotene in plants, there was no correlation between the amounts of lycopene and β-carotene in the different bacterial species. C50 pigments (bacterioruberins) were found only in pigmented extreme halophiles. There was no consistent correlation between the amounts of C40 and C50 compounds in these bacteria. This suggests that the latter may have a biosynthetic pathway independent of the former.Squalene, dihydrosqualene, and tetrahydr...

Pigments and isoprenoid compounds in extremely and moderately halophilic bacteria

The distribution of methane in an ombrotrophic bog was examined by extracting the gas from different depths, using evacuated bottles and sampling tubes. Methane was extracted during 75 min, from 60 cm, 90 cm and 120 cm depths at 25 stations in a 24 meter-square area. The amount of methane extracted varied widely between samples, and this variation was greater within each depth than between the different depths. Approximately two and a half times as much methane was found at 90 cm and 120 cm depths as at 60 cm. The amount of methane from sites more than 60 cm below the surface can be correlated with the methane microbially produced from peat from the same site during laboratory incubations. Much less methane could be extracted from near-surface peat than from deeper levels, but laboratory incubations of peat from this level produced 10-fold more methane. Our results show that there is a considerable amount of methane trapped below 50 cm depth within an ombrotrophic bog, which we calculate in the bog studied to be 1.7 Gg. We suggest this entrapped methane reduces the hydraulic conductivity in the lower layers of the peat by blocking the soil pore spaces and preventing fluid movement; this in turn generates an elevated water table allowing the formation of a raised bog. We further suggest that if this peat is disturbed by mining or farming, the entrapped methane could be released into the atmosphere and add to the atmospheric pollution by greenhouse gases.

An ombrotrophic bog as a methane reservoir

Acinetobacter O16, a psychrophilic species, produced extracelullar lipase (measured by hydrolysis of olive oil, tributyrin, or β-naphthyl laurate) when grown on a complex medium (peptone plus yeast...

Donn J. Kushner

Papers

The Biochemistry of archaea (archaebacteria)

Isolation and characterization of Actinopolyspora halophila, gen. et sp. nov., an extremely halophilic actinomycete.

Pigments and isoprenoid compounds in extremely and moderately halophilic bacteria

An ombrotrophic bog as a methane reservoir

Lipase and esterase formation by psychrophilic and mesophilic Acinetobacter species.