C O Obuekwe1, Z K Al-Jadi, E S Al-Saleh. 1. Microbiology Division, Department of Biological Sciences, Faculty of Science, Kuwait University, Safat, Kuwait City, Kuwait. okey@kuc01.kuniv.edu.kw
Abstract
AIMS: To investigate hydrocarbon degradation by hydrophobic, hydrophilic and parental strains of Pseudomonas aeruginosa. METHODS AND RESULTS: Partitioning of hydrocarbon-degrading P. aeruginosa strain in a solvent/aqueous system yielded hydrophobic and hydrophilic fractions. Exhaustive partitioning of aqueous-phase cells yielded the hydrophilic variants (L), while sequential fractionation of the hydrophobic phase cells yielded successive fractions exhibiting increasing cell-surface hydrophobicity (CSH). In hydrocarbon adherence assays (bacterial attachment to hydrocarbon), L had a value of 20%, which increased from 61.7% in first hydrophobic fraction (H(1)) to 72.2% in the third (H(3)). Crude oil degradation by L was 70%, but increased from 82% in H(1) to 93% in H(3). L variant produced most exopolysaccharides and reduced surface tension from about 73 to 49 mN m(-1). Rhamnolipid production was highest in L, but was not detected in all crude oil cultures. CONCLUSIONS: Hydrophobic subpopulations of hydrocarbon-degrading P. aeruginosa exhibited greater hydrocarbon-utilizing ability than hydrophilic ones, or the parental strain. SIGNIFICANCE AND IMPACT OF THE STUDY: Results demonstrate that a population of P. aeruginosa consists of cells with different CSH which affect hydrocarbon utilization. This potentially provides the population with the capacity to utilize different hydrophobic substrates found in petroleum. Judicious selection of such hydrophobic subpopulations can enhance hydrocarbon pollution bioremediation.
AIMS: To investigate hydrocarbon degradation by hydrophobic, hydrophilic and parental strains of Pseudomonas aeruginosa. METHODS AND RESULTS: Partitioning of hydrocarbon-degrading P. aeruginosa strain in a solvent/aqueous system yielded hydrophobic and hydrophilic fractions. Exhaustive partitioning of aqueous-phase cells yielded the hydrophilic variants (L), while sequential fractionation of the hydrophobic phase cells yielded successive fractions exhibiting increasing cell-surface hydrophobicity (CSH). In hydrocarbon adherence assays (bacterial attachment to hydrocarbon), L had a value of 20%, which increased from 61.7% in first hydrophobic fraction (H(1)) to 72.2% in the third (H(3)). Crude oil degradation by L was 70%, but increased from 82% in H(1) to 93% in H(3). L variant produced most exopolysaccharides and reduced surface tension from about 73 to 49 mN m(-1). Rhamnolipid production was highest in L, but was not detected in all crude oil cultures. CONCLUSIONS: Hydrophobic subpopulations of hydrocarbon-degrading P. aeruginosa exhibited greater hydrocarbon-utilizing ability than hydrophilic ones, or the parental strain. SIGNIFICANCE AND IMPACT OF THE STUDY: Results demonstrate that a population of P. aeruginosa consists of cells with different CSH which affect hydrocarbon utilization. This potentially provides the population with the capacity to utilize different hydrophobic substrates found in petroleum. Judicious selection of such hydrophobic subpopulations can enhance hydrocarbon pollution bioremediation.