Considering the Specific Impact of Harsh Conditions and Oil Weathering on Diversity, Adaptation, and Activity of Hydrocarbon-Degrading Bacteria in Strategies of Bioremediation of Harsh Oily-Polluted Soils

Abstract

Weathering processes change properties and composition of spilled oil, representing the main reason of failure of bioaugmentation strategies. Our purpose was to investigate the metabolic adaptation of hydrocarbon-degrading bacteria at harsh conditions to be considered to overcome the limitations of bioaugmentation strategies at harsh conditions. Polluted soils, exposed for prolonged periods to weathered oil in harsh soils and weather conditions, were used. Two types of enrichment cultures were employed using 5% and 10% oil or diesel as sole carbon sources with varying the mineral nitrogen sources and C/N ratios. The most effective isolates were obtained based on growth, tolerance to toxicity, and removal efficiency of diesel hydrocarbons. Activities of the newly isolated bacteria, in relation to the microenvironment from where they were isoalted and their interaction with the weathered oil, showed individual specific ability to adapt when exposed to such factors, to acquire metabolic potentialities. Among 39 isolates, ten identified ones by 16S rDNA genes similarities, including special two Pseudomonas isolates and one Citrobacter isolate, showed particularity of shifting hydrocarbon-degrading ability from short chain n-alkanes (n-C12–n-C16) to longer chain n-alkanes (n-C21–n-C25) and vice versa by alternating nitrogen source compositions and C/N ratios. This is shown for the first time.

Isolation, differentiation and biodiversity of ureolytic bacteria of Qatari soil and their potential in microbially induced calcite precipitation (MICP) for soil stabilization

“…There is a possibility that species with lower specic production needs more time to hydrolyse urea as compared to species with higher specic production due to a change in their conditions. 2 The hydrolysis of urea and the process of calcium carbonate precipitation are directly linked. 23 Calcium carbonate precipitation is present in the cultures in its regular (calcite) and irregular (amorphous) precipitate types.…”

Evidencing the diversity and needs of adjustment of the nutritional requirements for hydrocarbon-degrading activity of Pseudomonas aeruginosa adapted to harsh conditions using 2nfull factorial design

“…Their identication was performed using molecular techniques by sequencing the 16S rDNA as previously reported. 13 The selected strains were initially recovered from the established Qatari Hydrocarbon Degrading Strains Bank preserved in 30% glycerol in Luria-Bertani (LB) medium at À80 C, by streaking on solid LB medium. These strains were routinely streaked ahead for each experiment to obtain viable, fresh, and pure cells.…”

“…C/N ratios in each culture medium were calculated considering diesel as sole carbon source, and NH 4 NO 3 or NH 4 Cl as sole nitrogen source. Inoculation of the cultures was performed as previously reported by AlDisi et al 13 The initial biomass concentration at inoculation time was almost the same for all bacteria (2 Â 10 3 CFU ml À1 ). The produced biomass was calculated as the nal biomass from which the corresponding initial biomass was subtracted.…”

“…Isolation of three strains of P. aeruginosa was performed according to an isolation strategy of hydrocarbondegrading bacteria from weathered soils as previously showed. 13,14 A factorial experimental design was applied to investigate the correlation between growth parameters and hydrocarbon-degradation activity. The chosen model was Linear additive model for a Completely Randomized Design (CRD).…”

Biodegradation Kinetics of Benzene and Naphthalene in the Vadose and Saturated Zones of a (Semi)-arid Saline Coastal Soil Environment

“…Studies on biodegradation of PHCs in Qatari soils are very limited. The existing few studies include the work of Al Disi et al [29] who studied the effects of oil weathering due to long exposure to harsh weather conditions on the diversity, adaptation, and activity of hydrocarbon-degrading bacteria using contaminated soils from autoworkshops and industry waste management sites. In their study, with a purpose to help bioaugmentation strategies, the bacteria were isolated by growing them in the laboratory on the collected soils and using culture media with specific composition.…”