ABSTRACT

Interactions between epibiotic marine bacteria and their host organisms are known to play a significant role in many marine ecosystems but historically this association has received little attention. In this study, algal samples were collected subtidally by shallow water scuba techniques, and 51 bacterial epiphytes were isolated using novel culturing techniques New approaches to developing culture media were devised based upon using seaweed extracts from the marine algae, Fucus vesticulosus Isolated strains were evaluated for their potential to produce antimicrobial compounds specifically towards drug resistant pathogenic bacteria, especially methicillin resistant Staphylococcus aureus (MRSA) Preliminary results show that thirteen isolates produce inhibitory compounds towards methicillin susceptible Staphylococcus aureus of which one isolate (MH22) from Fucus vesiculosus showed good inhibition towards MRSA. The use of algae extract in the culturing of marine bacteria has proven successful as many of these bacteria are unable to grow on traditional marine media (Difco 2216E Marine Agar)

INTRODUCTION

There is high expectation that organisms from the marine environment will yield a vast array of new pharmaceutical compounds with novel activities that will provide new drugs in the fight against a number of microbial pathogens currently developing resistance to conventional antibiotic therapies.

In the past, many of our important antimicrobial compounds have been derived from terrestrial plants and micro-organisms For example, by the end of the 1980s 75% of the 20 most used hospital drugs and 20% of the top 100 drugs were derived from natural sources. However with the increase in the rate of emerging resistance among pathogenic bacterial populations, the earth's oceans will have the potential to provide a novel source of structurally unique bioactive agents because : (a) the oceans represent a much greater diversity of organisms and are estimated to contain up to 200,000 invertebrate and algal species and (b) research has shown that marine derived plants, animals and micro-organisms can produce a vast array of natural products with great diversity in chemical structure (1,2 & 3)

The extreme diversity of chemcal compounds found in the marine environment is thought to be due to competition between organisms for space, light and nutrients. As ecological niches are limited in the marine environment, primary colonizers have evolved the ability to produce noxious compounds to ward off potential competitors Marine invertebrates such as sponges have evolved complex relationships with microorganisms to produce compounds that enhance their rudimentary immune systems These compounds are known as secondary metabolites or " natural products " and provide an evolutionary advantage through prevention of predation and fouling as well as providing a means for organisms to gain a foothold for space light and nutrients. (2,3, & 4)

The production of antibiotics is of increasing importance because increasing numbers of bacteria are developing resistance to many conventional antibiotics. Many of these micro-organisms are able to undergo rapid mutations and so develop resistance to antibiotics, especially in closed environments such as hospitals where there is greater use of antibiotics than other environments

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