REEVALUATION OF THE HYPOTHESIS THAT BIODEGRADABLE SURFACTANTS STIMULATE SURFACE ATTACHMENT OF COMPETENT BACTERIA

The hypothesis that biodegradable surfactants stimulate the attachment of biodegradation-competent bacteria to surfaces has been re-evaluate d 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 al cohol dehydrogenase and alkylsulfatase complements (enzymes involved i n surfactant biodegradation), but differed markedly in its growth char acteristics 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, Pseudomo nas sp, DES2 did not attach to river sediment in a microcosm system wh en challenged with a dose of either surfactant, although it did biodeg rade 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 biod egradation of both substrates, is deregulated in Pseudomonas sp. DES2 in contrast to that in Pseudomonas sp, DES1, and that, contrary to a p revious hypothesis, biodegradable surfactants do not necessarily stimu late the attachment of biodegradation-competent bacteria during their biodegradation.