Derek Moormeir from University of Nebraska Medical Center
Presented Friday August 9, 2013
Staphylococcus aureus is an important bacterial pathogen that can cause a range of human infections, both in hospital and community settings. These persistent infections are exacerbated by biofilms, which are often recalcitrant to antibiotic therapy. The S. aureus cidABC and lrgAB operons have previously been shown to play specific roles in controlled cell death and release of extracellular DNA (eDNA) during biofilm maturation. Although the exact mechanisms controlling the cid and lrg operons have yet to be completely elucidated, it is known that the expression of the operons is dependent on altered metabolic cues as a result of overflow metabolism. In this study, we hypothesized that the differential expression of the cid and lrg operons within a biofilm is a function of the metabolic heterogeneity found within different biofilm microenvironments. To test this hypothesis, we constructed fluorescent cid and lrg promoter fusion strains to examine expression within a developing biofilm using the BioFlux 1000 microfluidic system. In support of the hypothesis, time-lapse epifluorescent images indicate that expression of these operons is specific to distinct regions of a growing biofilm. In addition, these results reveal the existence of different tower types, possibly reflecting their different functional roles in development. Together, the presence of distinct tower phenotypes suggests that there are both spatial and temporal differences between the tower structures and the remainder of the growing biofilm. Further insight into the potential metabolic differences between these tower structures and their effects on cid and lrg expression may lead to a unique perspective on biofilm development as well as the functional complexity of these multicellular structures.