title: Effects of rhamnolipids on cell surface hydrophobicity of PAH degrading bacteria and the biodegradation of phenanthrene.
abstract: The effects of rhamnolipids produced by Pseudomonas aeruginosa ATCC9027 on the cell surface hydrophobicity (CSH) and the biodegradation of phenanthrene by two thermophilic bacteria, Bacillus subtilis BUM and P. aeruginosa P-CG3, and mixed inoculation of these two strains were investigated. Rhamnolipids significantly reduced the CSH of the hydrophobic BUM and resulted in a noticeable lag period in the biodegradation. However, they significantly increased the CSH and enhanced the biodegradation for the hydrophilic P-CG3. In the absence of rhamnolipids, a mixed inoculation of BUM and P-CG3 removed 82.2% of phenanthrene within 30 days and the major contributor of the biodegradation was BUM (rapid degrader) while the growth of P-CG3 (slow degrader) was suppressed. Addition of rhamnolipids promoted the surfactant-mediated-uptake of phenanthrene by P-CG3 but inhibited the uptake through direct contact by BUM. This resulted in the domination of P-CG3 during the initial stage of biodegradation and enhanced the biodegradation to 92.7%.
authors.affiliation: Sino-Forest Applied Research Centre for Pearl River Delta Environment and Department of Biology, Hong Kong Baptist University, Hong Kong SAR, PR China.
authors.forename: Zhenyong
authors.initials: Z
authors.lastname: Zhao
authors.forename: Ammaiyappan
authors.initials: A
authors.lastname: Selvam
authors.forename: Jonathan Woon-Chung
authors.initials: JW
authors.lastname: Wong
mesh_terms: D000704:Analysis of Variance; D001412:Bacillus subtilis / Q000378:metabolism*; D001673:Biodegradation, Environmental / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D006017:Glycolipids / Q000378:metabolism / Q000494:pharmacology*; D057927:Hydrophobic and Hydrophilic Interactions / Q000187:drug effects*; D010616:Phenanthrenes / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D013501:Surface-Active Agents / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D006017:Glycolipids; D010616:Phenanthrenes; D013501:Surface-Active Agents; C418382:rhamnolipid; C031181:phenanthrene