Characterizing Biofilm Dispersion in the Gut Bacterium Enterococcus Faecalis

Authors: Raheema MohammedAbraham, Nermin Mohamed

Field of Study: Science, Technology, Engineering, and/or Math

Program Affiliation: McNair Scholars Program, NSF REU

Faculty Mentors: Peter McKenney

Easel: 32

Timeslot: Afternoon

Abstract: Biofilm dispersion is a survival mechanism where bacteria transition to a planktonic lifestyle. Dispersion is not characterized in Enterococcus faecalis (E. faecalis), a gut bacterium. In semi-batch cultures, E. faecalis formed steady state biofilms after 48 hours grown at 37°C in 10% Tryptic Soy Broth. Next, biofilm culture challenges with a 10-fold step increase in nutrients following 4 days of growth—prior to self-induced dispersion—resulted in statistically significant dispersion responses. To evaluate bile acids’ effect, dispersed cells were exposed to the primary and secondary bile acids cholic and lithocholic acid. Lithocholic acid retained biofilm growth during dispersion and thus may spur intestinal tract biofilm formation and preservation. Dose-finding assays were conducted with the oxazolidinone linezolid and glycopeptide vancomycin: E. faecalis displayed antibiotic tolerance to 50 µg/ml linezolid treatment, yielding a 0.5 log reduction. This study has revealed novel findings on the growth and dispersion response of E. faecalis biofilms.