Submitted to: Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2011
Publication Date: 6/9/2011
Publication URL: http://handle.nal.usda.gov/10113/55042
Citation: Burch, A.Y., Browne, P.J., Dunlap, C.A., Price, N.P., Lindow, S.E. 2011. Comparison of biosurfactant detection methods reveals hydrophobic surfactants and contact-regulated production. Environmental Microbiology. 13:2681-2691. DOI: 10.1111/j.1462-2920.2011.02534.x. Interpretive Summary: In this research, we screened bacteria from different ecological niches for surfactant production using a new assay. Bacterial surfactants are a diverse group of compounds that have important biological and industrial properties. They play an important role in bioremediation, petroleum extraction, and are useful as biopesticides. The current research demonstrated the utility of the new assay to screen bacteria for novel surfactants and determined the distribution of surfactant-producing bacteria in different ecological niches. This research benefits commercial interests seeking novel surfactants and benefits scientists by helping them understand the role these surfactants play in the bacterial colonization of different ecological niches. The ultimate goal is to understand how these molecules are used by plant pathogens or plant-associated bacteria in colonizing agriculturally important plants.
Technical Abstract: Biosurfactants are diverse molecules with numerous biological functions and industrial applications. A variety of environments were examined for biosurfactant-producing bacteria using a versatile new screening method. The utility of an atomized oil assay was assessed for a large number of bacterial isolates and compared with a commonlyused drop collapse assay from broth and plate cultures. The atomized oil assay detected every strain that produced a biosurfactant detectable by the drop collapse test, and identified additional strains that were not detected with the drop collapse assay because they produced low levels of surfactant or hydrophobic surfactants such as pumilacidins. Not all strains that produced a biosurfactant detectable by the drop collapse when cultured on agar surfaces produced surfactants detectable by drop collapse when cultured in broth, and vice versa. Many bacterial strains exhibited preferential production of surfactants when grown on an agar surface, and such surface enhancement of production could similarly be stimulated by increasing the viscosity of liquid culture media. Surface induction of surfactant production in Pseudomonas syringae was regulated at the transcriptional level. Surfactant production was much more common in bacteria recovered from terrestrial leaf and soil habitats (ca. 13% of strains) than in aquatic environments (ca. 5%).