BENEFICIAL MICROBES: PROBIOTICS DERIVED FROM THE SKIN OF ELEUTHERODACTYLUS JOHNSTONEI

Skin, whether animal or amphibian, is a barrier organ whose outermost surface is constantly in contact with the environment and faces ceaseless bombardment by potentially pathogenic microorganisms. Studies have demonstrated that healthy human skin (and arguably amphibian skin) possesses microflora colonies which are present in rather stable numbers and composition ranging between 102 and 107 microorganisms/cm2 depending on localization. Such microorganisms might represent probiotic microflora protecting the host from a number of different invasive bacteria. We were able to isolate 49 bacterial strains from the skin of several Eleutherodactylus johnstonei, a species of frog native to Grenada and widely distributed throughout the Caribbean. All of the isolated bacterial strains were subsequently examined for antimicrobial activity. In total, 5 out of the 49 isolates possessed antimicrobial properties and underwent a modified plug-test to quantitatively assess their inhibitory activity which was found to be statistically significant in comparison to our controls. The 5 isolates exhibited strong inhibitory action against both Gram-positive and Gram-negative pathogenic target organisms. The five bacterial strains in question have been identified as belonging to the genera Erwinia, Pseudomonas, Acinetobacter, Chryseomonas and Enterobacter. Given that the natural habitats of frogs are rife with bacteria, fungi and other potentially invasive microorganisms, it should not be surprising to find microflora on the surface of a frog’s skin. If resistant to the host’s antimicrobial defenses, and not causing any overt disease, these isolates may be involved in a symbiotic (and possibly mutualistic) relationship with their host

ANTIMICROBIAL PEPTIDES: A PARADIGM FOR NOVEL CHEMOTHERAPEUTIC AGENTS

Almost 80 years have passed since Dr. Alexander Fleming discovered penicillin, the first isolated antibiotic. However, due to improper usage, our once impressive array of antimicrobial agents is rapidly becoming ineffective. Infections that were once thought to have been conquered through the application of antibiotics have returned in the form of highly resistant strains. Indeed, hospitals worldwide have become inundated with, and a veritable breeding ground for, some of the most deadly bacteria. To combat this rapidly expanding problem, new and innovative antimicrobials must be found. The peptide defense systems of various species of amphibians have attracted considerable interest. The presence of numerous antimicrobial peptides in frog skin, acting separately or synergistically, may enhance survival in habitats laden with opportunistic and pathogenic microorganisms. This impressive peptide armament differs among frogs belonging to different families, genera, species and even subspecies. Results showed that no two species that have the same array of peptides have yet been found. Our study also demonstrated that Eleutherodactylus johnstonei, a species of frog native to Grenada and widely distributed throughout the Caribbean, does indeed produce antimicrobial peptides (preliminarily named Johnerin-1 and Johnerin-2) and that these peptides exhibit a broad spectrum of activity against target bacterial isolates. This project has the potential to open new avenues towards the development of novel chemotherapeutic agents and, at the very least, increase our understanding of the amphibian innate immune system

THE MICROBIAL DIVERSITY PRESENT IN A TROPICAL, CIRCUMNEUTRAL IRON SPRING IN GRENADA

Microbial evolution has allowed for microbial adaptation to many diverse and harsh environments. As a result, microbial diversity varies spatially, depending on the environmental pressures that are limiting. This research focused on uncovering the microbial diversity present in a Tropical Iron Spring in the Caribbean island, Grenada. Any microorganism from this island is expected to be genetically unique due to its spatial isolation and unique chemical composition of the water and gas in the Spring. The diversity was discovered using both culture dependent and culture independent techniques. Microorganisms were visualized and quantified using Florescence In Situ Hybridization (FISH) in conjunction with both florescent and light microscopy. Culture based analysis was used to isolate iron oxidizing autotrophic microbes. Temporal Gradient Gel Electrophoresis (TGGE) and Cloning were used to screen and isolate individual microbial species. Results indicated the possibility of microbes involved in carbon cycling, nitrogen cycling and iron cycling. In addition, the results point to the likelihood of a microbial community that is self-sustained or requires very few external resources. Such microbial ingenuity may help to provide greater knowledge on the aspects of energy conservation and mineral recyclin