(524c) Bacterial Response to Interfacial Stress in a Model of Hydrocarbon Bioremediation

Authors: 
Niepa, T. H. R., University of Pennsylvania
Vaccari, L., University of Pennsylvania
Leheny, R. L., Johns Hopkins University
Goulian, M., University of Pennsylvania
Lee, D., University of Pennsylvania
Stebe, K. J., University of Pennsylvania

Bacteria contribute in alleviating the persistent ecological impacts of oil spills by degrading hydrocarbons. When exposed to the oil-water interface the cells become trapped due to the high interfacial energies. We hypothesize that the interfacial stress induces changes in genetic pathways, leading to the formation of appropriate protective films or to the alteration of the metabolic performance of bacteria. Thus, this study contrasts the responses of Pseudomonas aeruginosa PAO1 and PA14 to hexadecane-water confinement to elucidate the effects of interfacial energy on the activity of the cells. Our results showed that P. aeruginosa PAO1 cells rapidly decreased the interfacial energy by self-assembling into thin Films of Bacteria at Interfaces (FBI), which have elastic and bending properties. In contrast, PA14 cells maintained a super-diffusive behavior at the oil-water interfaces, instead of forming FBI. While FBI formation by PAO1 was independent of cellular features involved in biofilm formation such as pili, flagellum, exopolysaccharides and biosurfactants, the deletion of some PA14 motility functions allowed the recovery of FBI. Changes in the transcriptional profile of the cells are further investigated using RNA sequencing to establish the pathways in P. aeruginosa that are affected by the interfacial confinements. The understanding of such differences in the response to interfacial stress is relevant to optimize the performance of the bacteria in the oil field, and thereby ameliorate ecosystem recovery.