Aaron M. T. Barnes

E-mail: barnesa@umn.edu

Year Entered: 2005

Degrees Received:
B.A., B.S., Biochemistry and Molecular Microbiology, The Evergreen State College, 2001

Thesis Advisor: Gary Dunny, Ph.D., MICaB Graduate Program

Thesis Research: 

The bacterium Enterococcus faecalis is a commensal organism in the intestinal tracts of many vertebrates and an opportunistic human pathogen. Naturally resistant to many common antibiotics – and able to acquire more resistance factors from the environment – E. faecalis is a growing concern in the hospital setting. Persistent infections often involve the formation of morphologically-complex bacterial colonies – biofilms – which add further limits to antibiotic effectiveness. In order to understand the genetic factors which control biofilm formation in E. faecalis, we need to improve our ability to accurately image the biofilm matrix.

My recent work in the Dunny lab has focused on low voltage field-emission scanning electron microscope imaging of cationic-dye stabilized E. faecalis biofilms to provide improved resolution in the investigation of what molecular constituents provide the biofilms structural framework. Work by other investigators in several related bacterial species have focused on the role of autologous DNA, work which I hope to extend to a series of E. faecalis mutant strains with interesting biofilm defects. In addition to examining the effectiveness of immunogold labeling techniques in determining the role extracellular DNA (eDNA) plays in the matrix, I plan to continue my optical microscopy work on confocal and deconvolution techniques to image live-cell biofilms, eventually extending to the use of specific fluorescent in-situ hybridization DNA probes to establish the dynamics of integration between eDNA and the polysaccharide/oligosaccharide components of the matrix.

Publications:

Kristich CJ, Nguyen VT, Le T, Barnes AMT, Grindle A, Dunny GM. Development and use of an efficient system for random mariner transposon mutagenesis to identify novel genetic determinants of biofilm formation in the core Enterococcus faecalis genome.  Appl Environ Microbiol. 74:3377-86.

Batra A, Hedden R C, Schofield P, Barnes A, Cohen C, Duncan T. Conformational behavior of guest chains in uniaxially stretched poly(diethylsiloxane) elastomers: 2H NMR and SANS. Macromolecules 2003;36:9458-66.