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The Function of Delta Proteobacteria

The phylum Proteobacteria is the largest phylum among bacteria with more than 2,000 distinct species. While the most diverse group, these complex microbes all share a gram-negative cell wall and represent the majority of gram-negative bacteria significant to medicine, industry and agriculture. The phylum is divided into five classes based upon their ribosomal RNA sequence, with each delineated by a Greek letter. Delta Proteobacteria are arranged into two orders, both of which are chemotrophic, meaning they obtain their energy from the oxidation of environmental elements as opposed to phototrophs, whose energy source is the sun. Both orders have distinct yet opposing implications for industry and biotechnology.

  1. Desulfovibrionales

    • The first order of Delta Proteobacteria are primarily strict anaerobes that prefer elemental sulfur or sulfur-containing compounds during anaerobic respiration. However, species have been found that are able to tolerate the presence of oxygen due to their oxygen-scavenging systems. They possess a flagellum for movement and cycle between a nongrowing predatory phase where feeding is its primary concern and an intracellular reproductive one. Desulvobivrionales are able to survive environments at extreme pH, until conditions become hospitable. They can be found in mud, polluted lake sediments and methane digesters, which are environmentally friendly anaerobic treatment lagoons that are able to generate biogas from agricultural waste through the utilization of anaerobic bacteria.

    Myxococcales

    • These second order Delta Proteobacteria are also gram-negative. They are aerobic and move by gliding. They are bacgteriolysins that scavenge upon other bacteria and yeast through the section of digestive enzymes that lyse the organisms cell wall. Myxococcales subsequently utilize the free peptides and amino acids as carbon and nitrogen sources for their own energy consumption. Their lifestyle is similar to slime molds and they can be found in neutral soils, decaying plant material and animal waste. They thrive in warm areas; however, have been found in such frigid environments as the Arctic tundra.

    Industrial Impact

    • Desulfovibrionales are a known menace to industry due to their chemotrophic preference for sulfur and sulfur-containing compounds. This leads to corrosion of any sulfur containing materials including iron in pipelines. Aerobic strains can generate sulfide gases that range from simple unpleasant odors to noxious gases that present dangers to humans under poorly ventilated conditions. Certain industries, particularly paper, are susceptible to these aerobic organisms, which can cause the degradation of paper products.

    Biotechnology Impact

    • Unlike Desulfovibrionales, Myxobacterial strains have been found to produce bio-active metabolites that possess antibacterial and antifungal properties, which can be isolated for use in medicine. One of particular interest is a natural antibiotic that can used to fight tuberculosis, which prevents that pathogen from synthesizing DNA and reproducing.

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