A desert soil sample was saturated with crude oil (17.3%, w/w) and aliquots were diluted to different extents with either pristine desert or garden soils. Heaps of all samples were exposed to outdoor conditions through six months, and were repeatedly irrigated with water and mixed thoroughly. Quantitative determination of the residual oil in the samples revealed that oil-bioremediation in the undiluted heaps was nearly as equally effective as in the diluted ones. One month after starting the experiment. 53 to 63% of oil was removed. During the subsequent five months, 14 to 24% of the oil continued to be consumed. The dynamics of the hydrocarbonoclastic bacterial communities in the heaps was monitored. The highest numbers of those organisms coordinated chronologically with the maximum oil-removal. Out of the identified bacterial species, those affiliated with the genera Nocardioides (especially N. deserti), Dietzia (especially D. papillomatosis), Microbacterium, Micrococcus, Arthrobacter, Pseudomonas, Cellulomonas, Gordonia and others were main contributors to the oilconsumption. Some species, e.g. D. papillomatosis were minor community constituents at time zero but they prevailed at later phases. Most isolates tolerated up to 20% oil, and D. papillomatosis showed the maximum tolerance compared with all the other studied isolates. It was concluded that even in oilsaturated soil, self-cleaning proceeds at a normal rate. When pristine soil receives spilled oil, indigenous microorganisms suitable for dealing with the prevailing oil-concentrations become enriched and involved in oil-biodegradation.

Two extreme halophilic Haloferax strains and one strain each of Halobacterium and Halococcus were isolated from a hypersaline coastal area of the Arabian Gulf on a mineral salt medium with crude oil vapor as a sole source of carbon and energy. These archaea needed at least 1 M NaCl for growth in culture, and grew best in the presence of 4 M NaCl or more. Optimum growth temperatures lied between 40 and 45 degrees C. The four archaea were resistant to the antibiotics chloramphenicol, cycloheximide, nalidixic acid, penicillin, streptomycin and tetracycline. The strains could grow on a wide scope of aliphatic and aromatic (both mono-and polynuclear) hydrocarbons, as sole sources of carbon and energy. Quantitative measurements revealed that these extreme halophilic prokaryotes could biodegrade crude oil (13-47%, depending on the strain and medium salinity), n-octadecane (28-67%) and phenanthrene (13-30%) in culture after 3 weeks of incubation. The rates of biodegradation by all strains were enhanced with increasing NaCl concentration in the medium. Optimal concentration was 3 M NaCl, but even with 4 M NaCl the hydrocarbon-biodegradation rates were higher than with 1 and 2 M NaCl. It was concluded that these archaea could contribute to self-cleaning and bioremediation of oil-polluted hypersaline environments.

Culture-dependent methods for bacterial community analysis are currently considered obsolete; therefore, molecular techniques are usually used instead. The results of the current study on hydrocarbonoclastic bacteria in various oily habitats in Kuwait showed however, that the bacterial identities varied dramatically according to the analytical approach used. For six desert and six seawater samples used in this study, the culture-independent and culture-dependent techniques each led to a unique bacterial composition. Problems related to the culture-dependent technique are well known. The results of the current study highlighted bias problems other than those already recorded in the literature for the molecular approaches. Thus, for example, in contrast to the culture-dependent technique, the primers used in the molecular approach preferentially amplified the 16S rDNAs of hydrocarbonoclastic bacteria in total genomic DNAs of all the studied environmental samples, and in addition, failed to reveal in any environmental sample members of the Actinobacteria. The primers used in the molecular approach also amplified certain “pure” 16S rDNAs, but failed to do so when these DNAs were in mixture. In view of these results, it is recommended that the two analytical approaches should be used simultaneously because their combined results would reflect the bacterial community composition more precisely than either of them can do alone.

Green animate materials from the intertidal zone of the Arabian Gulf coast accommodated more alkaliphilic and halophilic bacteria than inanimate materials. The alkaliphilic oil-utilizing bacteria, as identified by their 16S ribonucleic acid sequences, belonged to the following genera arranged in decreasing frequences: Marinobacter, Micrococcus, Dietzia, Bacillus, Oceanobacillus, and Citricoccus. The halophilic oil-utilizing bacteria belonged to the genera: Marinobacter, Georgenia, Microbacterium, Stappia, Bacillus, Isoptericola, and Cellulomonas. Most isolates could grow on a wide range of pure n-alkanes and aromatic compounds, as sole sources of carbon and energy. Quantitative gas liquid chromatographic analysis showed that individual isolates attenuated crude oil and representative pure hydrocarbons in culture. The optimum pH for most of the alkaliphilic genera was pH 10, and the optimum salinity for the halophiles ranged between 2.5 and 5% NaCl (w/v). It was concluded that as far as their microbial makeup is concerned, oily alkaline and saline intertidal areas of the Kuwaiti coasts have a self-cleaning potential.

Kuwaiti habitats with two-decade history of oil pollution were surveyed for their inhabitant oil-utilizing bacterioflora. Seawater samples from six sites along the Kuwaiti coasts of the Arabian Gulf and desert soil samples collected from seven sites all over the country harbored oil-utilizing bacteria whose numbers made up 0.0001-0.01% of the total, direct, microscopic counts. The indigenous bacterioflora in various sites were affiliated to many species. This was true when counting was made on nitrogen-containing and nitrogen-free media. Seawater samples harbored species belonging predominantly to the Gammaproteobacteria and desert soil samples contained predominantly Actinobacteria. Bacterial species that grew on the nitrogen-free medium and that represented a considerable proportion of the total in all individual bacterial consortia were diazotrophic. They gave positive acetylene-reduction test and possessed the nifH genes in their genomes. Individual representative species could utilize a wide range of aliphatic and aromatic hydrocarbons, as sole sources of carbon and energy. Quantitative determination showed that the individual species consumed crude oil, n-octadecane and phenanthrene, in batch cultures. It was concluded that the indigenous microflora could be involved in bioremediation programs without bioaugmentation or nitrogen fertilization. Irrigation would be the most important practice in bioremediation of the polluted soil desert areas.

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