abstract
Bioremediation efforts often rely on the application of surfactants to enhance hydrocarbon bioavailability. However, synthetic surfactants can sometimes be toxic to degrading microorganisms, thus reducing the clearance rate of the pollutant. Therefore, surfactant-resistant bacteria can be an important tool for bioremediafion efforts of hydrophobic pollutants, circumventing the toxicity of synthetic surfactants that often delay microbial bioremediation of these contaminants. In this study, we screened a natural surfactant-rich compartment, the estuarine surface microlayer (SML), for cultivable surfactant-resistant bacteria using selective cultures of sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB). Resistance to surfactants was evaluated by colony counts in solid media amended with critical micelle concentrations (CMC) of either surfactants, in comparison with non-amended controls. Selective cultures for surfactant-resistant bacteria were prepared in mineral medium also containing CMC concentrations of either CTAB or SDS. The surfactant-resistant isolates obtained were tested by PCR for the Pseudomonas genus marker gacA gene and for the naphthalene-dioxygenase-encoding gene ndo. Isolates were also screened for biosurfactant production by the atomized oil assay. A high proportion of culturable bacterioneuston was tolerant to CMC concentrations of SDS or CTAB. The gacA-targeted PCR revealed that 64% of the isolates were Pseudomonads. Biosurfactant production in solid medium was detected in 9.4% of tested isolates, all affiliated with genus Pseudomonas. This study shows that the SML is a potential source of surfactant-resistant and biosurfactant-producing bacteria in which Pseudomonads emerge as a relevant group.
keywords
POLYCYCLIC AROMATIC-HYDROCARBONS; SODIUM DODECYL-SULFATE; BIOSURFACTANT PRODUCTION; BACTERIAL COMMUNITIES; CATIONIC SURFACTANT; DEGRADING BACTERIA; CONTAMINATED SOIL; CARBON SOURCE; CRUDE-OIL; AERUGINOSA
subject category
Biotechnology & Applied Microbiology; Microbiology
authors
Louvado, A; Coelho, FJRC; Domingues, P; Santos, AL; Gomes, NCM; Almeida, A; Cunha, A
our authors
Patrícia Maia Domingues
PhD StudentGroups
acknowledgements
The authors are grateful to Fernando Fernandes for the airbrush used in the atomized oil assays and to two anonymous reviewers whose suggestions contributed to the improvement of the manuscript. This work was partially funded by the Centre for Marine and Environmental Studies (CESAM).