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Sea may be source of future medicines

Townsville, Queensland, Australia - A group of bacteria known as actinomycetes found living in coral reef sponges and marine sediments could be a rich source of future medical drugs, said Russell T. Hill, research professor, of the University of Maryland Biotechnology Institute (UMBI) here today.

"Soil-based actinomycetes produce over 70 percent of naturally occurring antibiotics. It is a group that are generally considered to be terrestrial but we have found a great diversity of new ones in marine environments," Hill reported at the International Marine Biotechnology Conference.

Hill and colleages at UMBI's Center of Marine Biotechnology in Baltimore, Md. and Nicole S. Webster of the Australian Institute of Marine Science (AIMS) used molecular techniques to identify bacteria from sponges of the Great Barrier Reef. Surprisingly, approximately 25 percent of the bacterial gene pieces found were from newly discovered actinomycetes. "This is an unexpectedly high proportion and indicates that marine sponges may be a good source of novel actinomycetes," concluded Hill.

In the past, many species of actinomycetes with bioactive compounds could be screened for antibiotics because they could be cultured in the laboratory, said Hill. "Fifty to sixty percent of a sponge's wet weight is bacteria," he said. "So we had to determining whether the positive results were from the sponge or it's bacteria."

The challenge now, he said, is to grow additional actinomycetes from sponges. Another approach is to clone genes from them. "Most of these antibiotic synthesis pathways are multiple gene pathways. So if you manage to move around the genes for antibiotic production, from say a very slow growing actinomycetes to a very rapidly growing fermentation strain to produce a new antibiotic in industry, it may be possible to produce the compound you are interested in," said Hill. "Isolating the compound-producing microbe or its genes is obviously a much better approach than trying to harvest and grow sponges, which is extremely difficult."

The researchers have also found diverse actinomycetes in tropical marine sediments from the Bahamas and Florida Keys, said Hill.

University of Maryland Biotechnology Institute. October 2000.