Aaron M.T. Barnes

     E-mail: barnesa@umn.edu

    Year Entered: 2005

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

     University of Minnesota
     Microbiology, Immunology and Cancer Biology
     Ph.D., 2012

     Honors and Awards:

     -Presidential Scholar Award, 2012 Microscopy and Microanalysis
     meeting (August 2012)

     Thesis Advisor: Gary Dunny, Ph.D.

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 (pubmed):

Frank KL, Barnes AM, Grindle SM, Manias DA, Schlievert PM, Dunny GM. Use of recombinase-based in vivo expression technology to characterize Enterococcus faecalis gene expression during infection identifies in vivo-expressed antisense RNAs and implicates the protease Eep in pathogenesis. Infect Immun. 2012 Feb;80(2):539-49.

Wells CL, Henry-Stanley MJ, Barnes AM, Dunny GM, Hess DJ. Relation between antibiotic susceptibility and ultrastructure of Staphylococcus aureus biofilms on surgical suture. Surg Infect (Larchmt). 2011 Aug;12(4):297-305.

Henry-Stanley MJ, Hess DJ, Barnes AM, Dunny GM, Wells CL. Bacterial contamination of surgical suture resembles a biofilm. Surg Infect (Larchmt). 2010 Oct;11(5):433-9.

Kristich CJ, Nguyen VT, Le T, Barnes AM, Grindle S, 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. 2008 Jun;74(11):3377-86.

Publications Prior to Entering MD/PhD Program:

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.