title: Indigenous soil bacteria with the combined potential for hydrocarbon consumption and heavy metal resistance.
abstract: BACKGROUND
  Transconjugant bacteria with combined potential for hydrocarbon utilization and heavy metal resistance were suggested by earlier investigators for bioremediation of soils co-contaminated with hydrocarbons and heavy metals. The purpose of this study was to offer evidence that such microorganisms are already part of the indigenous soil microflora.
  
  
  METHODS
  Microorganisms in pristine and oily soils were counted on nutrient agar and a mineral medium with oil as a sole carbon source, in the absence and presence of either sodium arsenate (As V), sodium arsenite (As III) or cadmium sulfate, and characterized via 16S rRNA gene sequencing. The hydrocarbon-consumption potential of individual strains in the presence and absence of heavy metal salts was measured.
  
  
  RESULTS
  Pristine and oil-contaminated soil samples harbored indigenous bacteria with the combined potential for hydrocarbon utilization and As and Cd resistance in numbers up to 4 × 10⁵ CFU g⁻¹. Unicellular bacteria were affiliated to the following species arranged in decreasing order of predominance: Bacillus subtilis, Corynebacterium pseudotuberculosis, Brevibacterium linens, Alcaligenes faecalis, Enterobacter aerogenes, and Chromobacterium orangum. Filamentous forms were affiliated to Nocardia corallina, Streptomyces flavovirens, Micromonospora chalcea, and Nocardia paraffinea. All these isolates could grow on a wide range of pure aliphatic and aromatic hydrocarbons, as sole sources of carbon and energy, and could consume oil and pure hydrocarbons in batch cultures. Low As concentrations, and to a lesser extent Cd concentrations, enhanced the hydrocarbon-consumption potential by the individual isolates.
  
  
  CONCLUSIONS
  There is no need for molecularly designing microorganisms with the combined potential for hydrocarbon utilization and heavy metal resistance, because they are already a part of the indigenous soil microflora.
authors.affiliation: Department of Biological Sciences, Faculty of Science, Kuwait University, PO Box 5969, Safat 13060, Kuwait.
authors.forename: Nida
authors.initials: N
authors.lastname: Ali
authors.forename: Narjes
authors.initials: N
authors.lastname: Dashti
authors.forename: Dina
authors.initials: D
authors.lastname: Al-Mailem
authors.forename: Mohamed
authors.initials: M
authors.lastname: Eliyas
authors.forename: Samir
authors.initials: S
authors.lastname: Radwan
mesh_terms: D000473:Alkanes / Q000378:metabolism; D001149:Arsenates / Q000494:pharmacology; D018053:Arsenites / Q000494:pharmacology; D001673:Biodegradation, Environmental; D019187:Cadmium Compounds / Q000494:pharmacology; D015169:Colony Count, Microbial; D004351:Drug Resistance; D006090:Gram-Negative Bacteria / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism; D006838:Hydrocarbons / Q000378:metabolism*; D007730:Kuwait; D019216:Metals, Heavy / Q000494:pharmacology*; D009994:Osmolar Concentration; D010578:Petroleum / Q000032:analysis / Q000378:metabolism; D059392:Petroleum Pollution; D010616:Phenanthrenes / Q000378:metabolism; D017670:Sodium Compounds / Q000494:pharmacology; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000494:pharmacology; D013431:Sulfates / Q000494:pharmacology
chemical_list: D000473:Alkanes; D001149:Arsenates; D018053:Arsenites; D019187:Cadmium Compounds; D006838:Hydrocarbons; D019216:Metals, Heavy; D010578:Petroleum; D010616:Phenanthrenes; D017670:Sodium Compounds; D012987:Soil; D012989:Soil Pollutants; D013431:Sulfates; C031181:phenanthrene; C017947:sodium arsenite; C009277:sodium arsenate; C037123:cadmium sulfate; C022883:octadecane