Comparison of the Degradation Activity of Biofilm-associated Versus Planktonic Cells
Masaaki Morikawa and Kenji Washio
from: Biofilms in Bioremediation: Current Research and Emerging Technologies (Edited by: Gavin Lear). Caister Academic Press, U.K. (2016) Pages: 219-232.
Biofilm formation is a common microbial strategy to construct and maintain a favorable niche in stressful natural environments. Consequently, the application of biofilms in bioproduction and bioremediation processes should be a natural and rational choice (Morikawa, 2006). In this chapter, we describe two examples that demonstrate the usefulness of biofilm-associated cells in bioremediation, and provide basic mechanisms that should advance environmental biotechnologies. First, Pseudoalteromonas strains were shown to be dominant biofilm forming bacteria in fish-farming fields and some produced extracellular proteases in a biofilm-dependent manner. The results suggest that Pseudoalteromonas bacteria living in the biofilm community, contribute in part to remove excess proteinaceous material from the sediment sludge and maintain good water quality in fish farms. Second, biofilm-associated cells of Pseudoalteromonas stutzeri T102 did not degrade naphthalene during initial hours of incubation but later they degraded it even faster than planktonic cells. This delayed but elevated degradation activity of the biofilm-associated cells could be attributed to 'super-activated cells' as they detach from biofilms. T102 biofilm-associated cells were capable of surviving for 10 weeks in natural petroleum-contaminated soils; by then T102 planktonic cells were mostly extinct. Naphthalene degradation activity in the soils that had been inoculated with T102 biofilms was indeed higher than that observed in soils inoculated with T102 planktonic cells. It would appear that biofilms may provide a constant stream of super-active contaminant degrading bacteria which could may be used in bioremediation applications read more ...