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

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 bacteriumPseudomonassp. DES1 designatedPseudomonassp. 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.Pseudomonassp. DES1 exhibited diauxie in these surfactant-based culture media in contrast toPseudomonassp. DES2, which exhibited single-phase growth.Pseudomonassp. 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,Pseudomonassp. 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 inPseudomonassp. DES2 in contrast to that inPseudomonassp. DES1, and that, contrary to a previous hypothesis, biodegradable surfactants do not necessarily stimulate the attachment of biodegradation-competent bacteria during their biodegradation.