(319d) Investigating the Interfacial and Metabolic Properties of Bacteria at Hexadecane-Water Interfaces

Hydrocarbonoclastic bacteria interact with oil-water interfaces in a manner that continues to be unveiled. To degrade hydrocarbons, cells must overcome the challenges of the energies existing at the oil-water interface. The cells become trapped between the two fluid phases that exert interfacial tensions and shear stresses on the cells. We hypothesize that cells develop a protective interfacial layer owing to their ability to metabolize one of the phases. We anticipate that primary oil-eating microbes would exhibit improved intrinsic properties enabling them to withstand the interfacial stress compared to non-indigenous species. Here, we examine the interfacial behavior of Alcanivorax borkumensis, a primary oil-eating marine isolate. Using pendant drop elastometry, we characterize the mechanical properties of films of bacteria at the hexadecane-water interfaces (FBI) to understand how cells alter the physicochemical properties of the interfaces. Our results demonstrate that A. borkumensis develops a film with viscoelastic properties characterized by frequency dependent storage and loss moduli. We further characterize the interfacial dynamics of A. borkumensis under chemical stress to comprehend how cell activity affects the mechanical properties of FBI. Our results demonstrate that cells responding to chemical stress exhibit increased tendencies to alter the interface with time. Furthermore, we correlate data in the pendant drop mode to flat interfaces with particle tracking and microrheology techniques. This two-system approach elucidates the biological implications interfacial bacterial films in a manner relevant to bioremediation.