Isolation of Surfactant-Resistant Bacteria from the Surface Microlayer

Bioremediation efforts sometimes rely on surfactants to enhance hydrocarbon bioavailability. However, synthetic surfactants are toxic to some degrading microorganisms. In this study we screened a natural surfactant-rich compartment, the sea surface microlayer (SML), for surfactant-resistant bacteria, using enrichment cultures of sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB). A random set of isolates obtained from enrichment cultures was tested by PCR for the Pseudomonas genus marker gacA gene and the ndo gene, encoding for PAH-degrading enzyme naphthalene dioxygenase. Results indicate a high abundance of surfactant resistant bacteria in the SML. An exponential increase in the number of culturable bacteria (7– 8 logs) was observed during the course of the enrichment culture. gacAtargeted PCR revealed that 30% of the surfactant-resistant isolates corresponded to Pseudomonads. However, amplification of sequences corresponding to ndogene involved in PAH-degrading pathways was not yet successful.