D B Steele

Auburn University, AUO, Alabama, United States

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Publications (6)31.36 Total impact

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    D B Steele · M D Stowers
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    ABSTRACT: The screening of microorganisms for the production of useful products continues to be an important aspect of biotechnology. Although advances in instrumentation, genetics, and microbial physiology are having an impact, screening programs are still primarily based on so-called classical techniques of enrichment and mutagenesis. One area that needs strengthening is the advancement of knowledge in microbial physiology. Recent surveys indicate that industry leaders see trained microbial physiologists as being the limiting factor in development of biotechnology in the coming decade. The largest impediment to development of new screening techniques is the ironic lack of programs specifically directed at developing new techniques. Too much emphasis is placed on using available techniques and relying on sheer labor and screening of vast numbers of organisms to produce novel products. In this respect, the Japanese are the exception and have proven that the establishment of new programs is worth the cost and effort. They are undoubtedly the world leaders in development of screening techniques and consequently the discovery of novel products. The isolation of microbes from novel and extreme environments holds tremendous promise in two areas. First, as Omura (46) and others (9, 48, 65) state, novel organisms will yield novel products. Second, such organisms serve as models for the understanding of structure and function that will facilitate the genetic manipulation of organisms and advance our ability to engineer novel enzymes. Hopefully such advances will enable genetic and protein engineering to have a greater impact on screening programs and techniques in the future. The earth holds a vast amount of varied and unique environments, from natural extremes such as high-altitude deserts and thermal springs, to manmade environments such as industrial-waste-treatment facilities, from which, with the appropriate methods and techniques, we may isolate and evaluate new potential products.
    Preview · Article · Feb 1991 · Annual Review of Microbiology
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    J J Lauff · D B Steele · L A Coogan · J M Breitfeller
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    ABSTRACT: A pure culture of an Agrobacterium sp. (deposited as ATCC 55002) that mineralizes the ferric chelate of EDTA (ferric-EDTA) was isolated by selective enrichment from a treatment facility receiving industrial waste containing ferric-EDTA. The isolate grew on ferric-EDTA as the sole carbon source at concentrations exceeding 100 mM. As the degradation proceeded, carbon dioxide, ammonia, and an unidentified metabolite(s) were produced; the pH increased, and iron was precipitated from solution. The maximum rate of degradation observed with sodium ferric-EDTA as the substrate was 24 mM/day. At a substrate concentration of 35 mM, 90% of the substrate was degraded in 3 days and 70% of the associated chemical oxygen demand was removed from solution. Less than 15% of the carbon initially present was incorporated into the cell mass. Significant growth of this strain was not observed with uncomplexed EDTA as the sole carbon source at comparable concentrations; however, the ferric chelate of propylenediaminetetraacetic acid (ferric-PDTA) did support growth.
    Full-text · Article · Dec 1990 · Applied and Environmental Microbiology
  • D. Bernie Steele · K. Ramirez · M. D. Stowers
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    ABSTRACT: Optimum growth conditions and inoculation regimes were determined for severalFrankia strains isolated from both Alnus and Casuarina host plants. Growth conditions were estabilished that allowed a reduction in generation time to less than 15 hours for certain Alnus derivedFrankia. Differences in plant growth response were observed with differing inoculum levels and soil mixtures. Elite strains of Alnus derivedFrankia were isolated that elicited similar growth reponses in allAlnus species tested; however, differences were observed betweenFrankia strains and plant growth response of variousCasuarina species tested.
    No preview · Article · Aug 1989 · Plant and Soil
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    ABSTRACT: When growing on N(2), actinomycetes from the genus Frankia form multicellular structures that contain nitrogenase. The structures are referred to as vesicles and are indistinguishable from vesicles formed when Frankia sp. are in root-nodule symbioses. Vesicles isolated from N(2)-grown cells of Frankia sp. strain CpI1 had a significantly higher amount and different composition of fatty acids than did vegetative cells recovered from NH(4) (+)-containing medium. Lipids from vesicles, whole cells grown on N(2), and whole cells grown on NH(4) (+) were fractionated by silicic acid chromatography into neutral lipids, glycolipids, and polar lipids. The fatty acids were transesterified by methanolysis and analyzed by gas chromatography and mass spectrometry. Vesicles had considerably higher amounts of fatty acids in the neutral and glycolipid fractions but lower amounts of polar lipid fatty acids than did vegetative cells. Polar lipids from vesicles had a higher proportion of mono-unsaturated and cyclopropane fatty acids and a lower proportion of isobranched fatty acids than did polar lipids from NH(4) (+)-grown or N(2)-grown cells. The neutral lipid and glycolipid fractions contained several long-chain compounds with molecular ions at m/z 408 and 410. The proportions of these compounds were significantly higher in the lipids from vesicles than from vegetative cells. These results suggest that lipids in vesicles might be involved in the protection of nitrogenase from O(2) and suggest a parallel with the glycolipids involved in protecting nitrogenase from O(2) in the cyanobacterial heterocysts.
    Full-text · Article · Jun 1989 · Proceedings of the National Academy of Sciences
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    ABSTRACT: A clinical isolate and a soil isolate of Chromobacterium violaceum were compared to determine differences in virulence-related characteristics. Purified lipopolysaccharide (endotoxin) from the virulent, clinical strain was more reactive than that from the avirulent soil strain as determined by the Limulus amebocyte lysate assay. There were no differences in hemolysin or cyanide production between the two strains. The virulent strain was more resistant to phagocytosis and intracellular killing by human polymorphonucleocytes. The clinical strain showed a superoxide dismutase activity 30% higher and a catalase activity fivefold higher than the activities of the soil-isolated strain. The clinical strain also was capable of producing approximately twice as much hydrogen peroxide during growth as compared with the soil isolate. This study suggests that virulence of C. violaceum may be, at least in part, associated with endotoxin, and some protection of the virulent, clinical strain from phagocytic attack is afforded by elevated levels of superoxide dismutase and catalase.
    Preview · Article · Apr 1988 · Canadian Journal of Microbiology
  • M. D. Stowers · R. K. Kulkarni · D. B. Steele
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    ABSTRACT: Frankia isolate NPI 0136010 was able to use only propionate and acetate as sole carbon sources and was unable to use hexoses, pentoses, disaccharides, and trisaccharides. Cell free extracts were surveyed for key enzymes of intermediary carbon metabolism. Enzymes of the Embden-Meyerhof-Parnas (EMP) pathway, the tricarboxylic acid (TCA) cycle and glyoxylate shunt were detected while enzymes of the pentose phosphate (PP) and Entner-Doudoroff (ED) pathways were absent. Malic enzyme was present allowing for the conversion of malate to pyruvate and gluconeogenesis. Radiorespirometric analysis confirmed the operation of the TCA cycle and established the methylmalonyl pathway as the route of propionate metabolism. The uptake of propionate was active and mediated by sulfhydryl groups.
    No preview · Article · Dec 1985 · Archives of Microbiology

Publication Stats

157 Citations
31.36 Total Impact Points


  • 1988-1991
    • Auburn University
      • College of Sciences and Mathematics
      AUO, Alabama, United States
  • 1989
    • The University of Tennessee Medical Center at Knoxville
      Knoxville, Tennessee, United States