Enrichment of rhizospheres of crop plants raised in oily sand with hydrocarbon-utilizing bacteria capable of hydrocarbon consumption in nitrogen free media

The rhizospheres of the three legume crops peas beans and peanuts and the three nonlegume crops sunflower tomato and mallow raised in pristine sand were associated with between 1 and 1 4 x 10(6) hydrocarbon-utilizing bacteria per gram root These values were much higher when the plants were raised in oily sand Thus numbers of the hydrocarbon-utilizing rhizobacteria of the legume crops ranged between 21 2 and 501 x 10(6) cells g(-1) roots and of the nonlegumes sunflower and tomato only between 65 and 87 x 10(6) cells g(-1) roots According to their 16S rRNA gene sequences the predominant oil-utilizing bacteria in rhizospheres of the legumes pea and beans were affiliated with Microbacterium oxydans Pseudomonas plecoglossicida and Acidovorax delafieldu Other minor oil-utilizing bacteria were also identified and recorded Pure cultures of all these bacteria could consume crude oil n-octadecane (an aliphatic hydrocarbon) and phenanthrene (an aromatic hydrocarbon) in nitrogen containing but also in nitrogen free media The latter finding suggests that these organisms may be self sufficient regarding their nitrogen nun [non It was therefore concluded that the use of legume crops for phytoremediation of oily desert soils through rhizosphere technology saves the use of nitrogen fertilizers making the phytoremediation process more economical and environmentally friendly (C) 2010 Elsevier Ltd All rights reserved