n-Alkane uptake and utilisation by Streptomyces strains

Streptomyces strains isolated from the Kuwait Burgan oil field were defined as S. griseoflavus, S. parvus, and S. plicatus utilised n-hexadecane, n-oc tadecane (purified fractions of mineral oil), kerosene, and crude oil as so le carbon and energy sources. The strains were incubated with n-alkanes and increase of the fatty acid content with chain length equivalent to the emp loyed n-alkanes was observed. Signal transducing GTP-binding proteins (GBPs ) play an important role in n-alkane uptake in streptomycetes. Specific act ivators of GBPs increased the uptake of hydrocarbons. Using the hydrophobic fluorescent dye diphenylhexatrien (DPH) as a probe, it was found that the microviscosity of the hydrophobic inner region of the cellular membrane is significantly lower in hydrocarbon utilisers than in non-utilisers. This di fference probably reflects differences in the fatty acid composition of the strains. When cultures were grown in n-alkane containing media, electron m icroscopy revealed that the hydrocarbon utilisers showed less-electron dens e areas as inclusions in the cytoplasm. Soil samples inoculated with Strept omyces strains eliminated hydrocarbons much faster than those not containin g these strains, serving as control. When inorganic medium was supplied wit h n-hexadecane-1-C-14 as sole carbon and energy source, radioactive CO2 was detected. Since streptomycetes have not been used until now for oil elimin ation, though they are known as abundant soil bacteria tolerating extreme c onditions, their possible use for bioremediation of hydrocarbon contaminate d soils is discussed.