Variability in Pseudomonas aeruginosa Lipopolysaccharide Expression during Crude Oil Degradation

Abstract

Bacterial utilization of crude oil components, such as the n-alkanes, requires complex cell surface adaptation to allow adherence to oil. To better understand microbial cell surface adaptation to growth on crude oil, the cell surface characteristics of two Pseudomonas aeruginosa strains, U1 and U3, both isolated from the same crude oil-degrading microbial community enriched on Bonny Light crude oil (BLC), were compared. Analysis of growth rates demonstrated an increased lag time for U1 cells compared to U3 cells. Amendment with EDTA inhibited U1 and U3 growth and degradation of the n-alkane component of BLC, suggesting a link between cell surface structure and crude oil degradation. U1 cells demonstrated a smooth-to-rough colony morphology transition when grown on BLC, while U3 cells exhibited rough colony morphology at the outset. Combining high-resolution atomic force microscopy of the cell surface and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extracted lipopolysaccharides (LPS), we demonstrate that isolates grown on BLC have reduced O-antigen expression compared with that of glucose-grown cells. The loss of O-antigen resulted in shorter LPS molecules, increased cell surface hydrophobicity, and increased n-alkane degradation.Among the hydrocarbon-utilizing bacteria, Pseudomonas aeruginosa is one of the most frequently isolated from hydrocarbon-impacted environments (4, 31). Due to the low aqueous solubility of n-alkanes, the ability of P. aeruginosa to oxidize this fraction of crude oil depends on direct cell-substrate contact (12, 31). Bacterial utilization of hydrophobic compounds requires cell surface adaptation to overcome forces interfering with direct cell-substrate contact. In gram-negative bacteria, the outer membrane is the initial cell component to contact substrates and is directly impacted by cell culture conditions, such as temperature, pH, and nutrient availability (7). Understanding bacterial adaptation of the outer membrane may provide insight into attachment to and utilization of hydrophobic compounds.In P. aeruginosa, variation in the lipopolysaccharide (LPS) molecules of the outer membrane influences cell surface hydrophobicity (2, 22). The amphipathic nature of LPS molecules results from three covalently linked components, a hydrophobic lipid A region, a core oligosaccharide, and a repeating O-polysaccharide (or O-antigen) portion (37). The O-antigen region contacts the surrounding environment and directly impacts nonspecific cell surface properties, such as hydrophobicity (22, 27). P. aeruginosa coexpresses two distinct LPS types, A-band and B-band LPS (20, 28). The shorter A-band LPS is composed of 23 D-rhamnose trisaccharide repeating units, while the longer B-band LPS contains numerous monosaccharides arranged as di-to pentasaccharide units. While the Bband LPS often masks the underlying A-band molecules, variations in growth conditions can alter LPS expression, resulting in changes in cell surface properties. P. aeruginosa growth on n-hexadecane results in an overall...

Effect of Pyocyanin on a Crude-Oil-Degrading Microbial Community

“…To generate the oil used in this study, n-alkane-containing oil (Bonny Light Crude [BLC]; 56% saturates, 31% aromatics, 11% polars, 2% asphaltenes, 35.3°API gravity) was predegraded for 30 days with a coculture of P. aeruginosa (20,31). The remaining oil was extracted three times with dichloromethane, dried over sodium sulfate, and analyzed by gas chromatography (GC) with flame ionization detection (FID).…”

Biodegradation of Low Density Polythene (LDPE) by Pseudomonas Species

“…However, the effect of natural environment was shown to be more pronounced than in vitro conditions due to the presence of bacterial and fungal consortium in the former [2]. Norman et al [7] and Tadros et al [12] have previously reported on the biodegradability potential of Pseudomonas aeruginosa, Pseudomonas fluorescens and fungi Penicillium simplicissimum on synthetic plastics. Concurrently, it has also been postulated that the biodegradation of any synthetic material initiates with the colonization of microorganism on the surface of the material [8].…”

Degradation of long-chain n-alkanes (C36 and C40) by Pseudomonas aeruginosa strain WatG

“…Ko and Lebeault (1999) demonstrated that P. aeruginosa K1 and Rhodococcus equi P1 were able to degrade alkanes of chain lengths from C 7 to C 28 . Although crude oil degradation by P. aeruginosa was reported (Abalos et al, 2004;Norman et al, 2002), the fate of the very long chain n-alkane components was not described. Wongsa et al (2004) isolated a petroleumdegrading strain of P. aeruginosa that had the ability to degrade a broad range of hydrocarbons.…”