Renee Saville, graduate student
Abstract
Microbial biofilms are ubiquitous and in addition to their presence in the natural environment, they profoundly impact all manner of human endeavors. Stages in the development of a biofilm include initial attachment of cells to a surface, growth of bacteria on that surface and secretion of extracellular polymeric substances, further maturation of biofilm architecture, and eventual sloughing of biomass from the biofilm once it reaches a critical size. Cell shedding into the aqueous environment occurs throughout this process, but it has been observed that widespread shedding of cells-termed detachment-can be induced under certain conditions. Detachment is the least understood stage in biofilm growth, but it is critical for many environmental processes.?
Shewanella oneidensis strain MR-1, a non-fermenting facultative microorganism that can use a variety of electron acceptors under anoxic conditions, readily forms biofilms in laboratory-built flow cells.? S. oneidensis is a dissimilatory metal reducing bacterium, and as such plays an important role in element cycling and potentially in the remediation of certain contaminants. This research elucidated the principle molecular components involved in S. oneidensis biofilm formation. Laboratory-grown biofilms of MR-1 rapidly disintegrate upon a loss of media flow through the chamber, and we determined that oxygen depletion is a major trigger for the detachment. A second major branch of this research was the physiological characterization of biofilm detachment including its energy requirement, gene expression-dependency and the role of a secondary messenger molecule, cyclic-di-GMP.?
An understanding of inducible detachment in biofilms found in a variety of settings-and the ability to therefore influence biofilm dynamics-is potentially very important. Results may have applications in the use of medical implants, corrosion and water treatment processes.
This seminar comprises the public portion of Ms. Saville's university Ph.D. thesis defense.