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Re-evaluation of the hypothesis that biodegradable surfactants stimulate surface attachment of competent bacteria

Sarah A. Owen^1,

Nicholas J. Russell^1,

¹School of Molecular and Medical Biosciences, Biochemistry Unit, University of Wales Cardiff, PO Box 911, Cardiff CF1 3US, UK
²Institute of Freshwater Ecology, River Laboratory, East Stoke, Wareham, Dorset BH20 6BB, UK

³Author for correspondence: Graham F. White. Tel: +44 1222 874188. Fax: +44 1222 874116. e-mail: smbgfwl@cardiff.ac.uk

ABSTRACT

The hypothesis that biodegradable surfactants stimulate the attachment of biodegradation-competent bacteria to surfaces has been re-evaluated using a variant of the surfactant-degrading bacterium Pseudomonas sp. DES1 designated Pseudomonas sp. DES2. This variant was identical to the parental strain in terms of its carbon-utilization patterns and alcohol dehydrogenase and alkylsulfatase complements (enzymes involved in surfactant biodegradation), but differed markedly in its growth characteristics when using sodium dodecyl triethoxysulfate or triethylene glycol dodecyl ether as secondary carbon sources. Pseudomonas sp. DES1 exhibited diauxie in these surfactant-based culture media in contrast to Pseudomonas sp. DES2, which exhibited single-phase growth. Pseudomonas sp. DES2 did not attach to river sediment in a microcosm system when challenged with a dose of either surfactant, although it did biodegrade the substrate. In contrast, Pseudomonas sp. DES1 attached to the river sediment whilst biodegrading the test substrate. It is concluded that the ether-scission system, which is responsible for primary biodegradation of both substrates, is deregulated in Pseudomonas sp. DES2 in contrast to that in Pseudomonas sp. DES1, and that, contrary to a previous hypothesis, biodegradable surfactants do not necessarily stimulate the attachment of biodegradation-competent bacteria during their biodegradation.

Present address: Microbiology Laboratories, Department of Biological Sciences, Wye College, University of London, Wye, Ashford, Kent TN25 5AH, UK.

Present address: Research School of Biosciences, The University, Canterbury, Kent CT2 7NJ, UK.