Thousands of unique plant and animal species inhabit the Hawaiian Archipelago, but novel microorganisms in the region have only been reported occasionally during the last thirty years. Novel cultivated microorganisms are widely considered to be potential sources of new secondary metabolites, some of which may inhibit the growth of other microorganisms. In this respect, although relatively few marine fungi and yeasts have been described globally, several have proven to be sources of unique bioactives. To explore the secondary metabolite potential of the Hawaiian mycoflora in this respect, we have cultivated fungi and yeasts from diverse Hawaiian marine habitats, and commenced screening for antibiotic and cytotoxic metabolites. We have combined a traditional approach of preliminary screening of strains grown in pure culture, with one of challenging cultures with dead pathogens in order to encourage the production of secondary metabolites. Culture media from over 100 pure and challenged Hawaiian marine fungi and yeast strains have been screened for antibacterial and cytotoxic activities. Cultures of fungi and yeast, either pure or in the presence of heat-killed vancomycin-resistant enterococci (VRE), or methicillin-resistant Staphylococcus aureus (MRSA), are dried, extracted with methanol and further concentrated. Crude extracts are applied to live cultures of the same pathogens in a 96-well plate assay. Growth of the pathogens in the presence of extracts is measured by changes in turbidity, and compared to that of each pathogen in the presence of known concentrations of antibiotics. Up to one-third of all extracts tested to date have demonstrated greater inhibition of VRE and MRSA than positive controls, i.e., those with a lethal concentration of a commercial antibiotic. Testing against brine shrimps has shown some extracts to be potent cytotoxins. Initial screens against VRE and MRSA have been encouraging, and we are preparing to determine the structures of some of the most active ‘extracts’.
Presenter:
Stuart P. Donachie, Ph.D.
Assistant Professor
Department of Microbiology
University of Hawaii at Manoa
Friday May 6, 2005
POST 723
11:00 a.m.
Refreshments will be served after the seminar in POST 121
The Pacific Research Center for Marine Biomedicine (PRCMB) is a newly established center at the University of Hawaii dedicated to trans-disciplinary research designed to gain new knowledge about the profound impacts of the ocean on human health. The Center is funded by the National Science Foundation (OCE04-32479) and the National Institute of Environmental Health Sciences (P50ES012740).
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