Abstract
The discovery of antibiotics, even some of it being accidental has led to a dramatic change in the course of medicine and clinical treatments. Since their discovery antibiotics have been used to treat bacterial infections which would otherwise claim the lives of many. For many decades the use of these compounds made the jobs of physicians much easier when it came to treatment of bacterial pathogens, some even termed it the "Antibiotics golden age". Because of the sometimes-careless prescribing of antibiotics by physicians or the patients not following the correct regiment, many of the pathogenic bacteria have become resistant to antibiotic treatment. The incomplete eradication of some pathogens has allowed the surviving ones to develop resistance to conventional antibiotic treatment, thus calling for more potent antibiotics. The increasing resistance has thus far proven to occur at a faster rate than the development of more potent and effective antibiotics which is creating an issue in the medical world and in clinical settings. Because of this the "Golden Age of Antibiotics" appears to be ending. Because of this arising issue there have been many novel approaches by scientists which have looked at how to effectively target pathogenic bacteria without the occurrence of resistance. An approach to this issue has been quorum sensing and its inhibition in pathogenic bacteria. Quorum sensing is a mechanism that is used by many Gram-negative bacteria to communicate and regulate expression of certain genes and was first discovered in bobtail squid where Vibrio fischeri, a Gram-negative bacterium would turn on gene expression to induce bioluminescence causing glowing. Quorum sensing becomes problematic when the expression of genes that it induces are pathogenic, as is the case in Pseudomonas aeruginosa. It has been hypothesized that some bacteria produce compounds that regulate quorum sensing in their environment which regulates population densities. During experiments it was shown that Cellulophaga spp. a marine isolate was able to inhibit quorum sensing in a reporter system. Its secreted molecules were used to test its efficacy on inhibiting quorum sensing. The secreted molecules produced by Cellulophaga spp. or termed E6 were studied and isolated via centrifuging and microfiltration. Their efficacy was shown against a reporter assay and it was shown that there are three molecules present, of which two of them are seen active, from previous assays. A scale up of E6 growth was completed so that enough molecules can be gathered for structural analysis. Structural analysis was done via column chromatography which allowed for polarity separation of the compounds. In addition, the molecules were ran via NMR to identify structure. Biofilm and LasB assays show that the active compounds from E6 inhibits quorum sensing from occurring. A mutant screening was done to try and figure out which genes in E6 are responsible for quorum sensing inhibition. This research will add to the overall library of quorum sensing inhibitory compounds and will help with the research toward developing novel antibacterial compounds.