Assimilation of Hydrocarbons by Pseudomonas Strains Isolated from Human Clinical Specimens

Twenty strains of Pseudomonas isolated from human clinical specimens on routine laboratory media, without hydrocarbon enrichment and unselected for their growth on hydrocarbons, were tested for their ability to utilize a series of eight n-alkanes and two 1-alkenes as a sole carbon and energy source for growth. Hydrocarbon assimilation does occur with such isolates relative to the chain length and the degree of saturation of the hydrocarbon. The data presented show that all 16 stains of Pseudomonas aeruginosa studied grew readily on dodecane through hexadecane and on 1-hexadecene. In addition, most strains of this species grew on undecane and 1-dodecene after prolonged incubation. There was a long lag period, usually a minimum of 4 days, before onset of growth on any hydrocarbon. In no case did hexane or decane support growth. Two strains each of P. maltophilia and P. stutzeri were unable to grow on any of the hydrocarbons tested. Hexane in concentrations above 1% (vol/vol) is bactericidal toward the Pseudomonas inoculum. It is toxic even to cells utilizing different hydrocarbon for growth. The addition of 1% hexane to 1% (vol/vol) hexadecane markedly prolonged the lag phase of P. aeruginosa utilizing the hexadecane for growth.