123-456-7890
Biofilm Research
Biofilms are a main source of infection throughout the body. Biofilm infections are especially dangerous because of their increased levels of antibiotic tolerance, as compared to planktonic bacterial populations. This semester, our team is looking deeper at one of the mechanisms biofilms utilize to increase their tolerance for antibiotics: outer membrane vesicles. Outer membrane vesicles, or OMVs, are small, membranous sacs that effectively bleb off of the bacterial membrane. They are used to transfer macromolecules and other products from one bacteria to another. Also, since their membranes are identical to the bacterial membranes, they act as decoys to the antibiotics, saving the biofilm.
In order to test just how important theses OMVs truly are in antibiotic tolerance, we studied three strains this semester: Pseudomonas aeruginosa 14 as our wild type control, and its mutants pqsA and pqsH. The two mutants have deletions in two separate areas of a specific signaling operon in which the end product is the pseudomonas quinolone signal (PQS). This signaling molecule has been found to directly affect levels of OMV production. By lowering levels of PQS production, we hoped to lower levels of OMV production as well, therefore lowering antibiotic tolerance. This theory was tested on late-stage biofilms grown for 5 days in a biofilm tube reactor on 1:20 LB. The antibiotics we used to test tolerance were colistin, ciprofloxacin, and tobramycin, each chosen for their separate antimicrobial abilities. Colistin interacts directly with the outer membrane of the bacterial cells. Ciprofloxacin inhibits type II DNA topoisomerase, leading to a lack of mRNA synthesis. Tobramycin affects bacterial ribosome activity.
After running nine trials of biofilm tube reactors, it was found that there was no statistical difference between the log reductions of PA14 wt and mutants. This suggests that OMVs are not contributors to antibiotics tolerance, which is contradictory to previous literature. ANOVA statistical analysis also showed that there was a significant difference between log reduction between Ciproloxacin and Tobramycin, and Ciprofloxacin and Colistin. However there was no statistical difference between Colistin and Tobramycin which was supportive of the MICs This research can be used to further knowledge on OMVs, with hopes that in the future, OMVs can be used to our benefit. By finding a way around the decoy, we can learn to better destroy biofilms to preserve our health.
