Enhanced haloarchaeal oil removal in hypersaline environments via organic nitrogen fertilization and illumination

Hypersaline soil and pond water samples were mixed with 3 % crude oil, some samples were autoclaved to serve as sterile controls; experimental samples were not sterilized. After 6-week incubation at 40 A degrees C under light/dark cycles, the soil microflora consumed 66 %, and after 4 weeks the pond water microflora consumed 63 % of the crude oil. Soil samples treated with 3 % casaminoacids lost 89 % of their oil after 6 weeks and water samples lost 86 % after 4 weeks. Samples treated with casaminoacids and antibiotics that selectively inhibited bacteria, lost even more oil, up to 94 %. Soil-water mixtures incubated under continuous illumination lost double as much more oil than samples incubated in the dark. The soil-water mixture at time zero contained 1.3 x 10(4) CFU g(-1) of hydrocarbon-utilizing microorganisms which were affiliated to Halomonas aquamarina, Exiguobacterium aurantiacum, Haloferax sp., Salinococcus sp., Marinococcus sp. and Halomonas sp. After 6-week incubation with oil, these numbers were 8.7 x 10(7) CFU g(-1) and the Haloferax sp. proportion in the total microflora increased from 20 to 93 %. Experiments using the individual cultures and three other haloarchaea isolated earlier from the same site confirmed that casaminoacids and light enhanced their oil consumption potential in batch cultures.