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Volume 5, Number 1
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Medicine from Microbes

By Erica Goldman

Barrel sponge - photo by Ruseell Hill

From the exotic waters of Indonesia, come microbe-rich sponges like this one (Xestospongia testudiniaria). UMBI microbiologist Russell Hill scours these sponges for bacteria that can produce compounds promising for medicine. Photo by Ruseell Hill.

Symbiotic relationships between bacteria and other marine creatures may prove a treasure trove for drugs from the sea. Bacteria associated with sponges and sea slugs may harbor new treatments for malaria and cancer.

Russell Hill, a marine microbiologist at the University of Maryland Biotechnology Institute's Center of Marine Biotechnology, has discovered two novel bacterial symbionts. One lives inside an Indonesian sponge and produces a compound with anti-malarial properties; the other lives inside a small sea slug (called a sacoglossan) and produces a peptide with promising anti-cancer activity, currently in Phase II clinical trials in Europe.

The key is to divorce the drug-producing microbe from its sometimes-scarce host. This may make all the difference for drug development, says Hill. Growing the bacteria in the lab is cheap relative to finding and harvesting it from the animal itself, and lab culture offers the opportunity to make genetic modifications once the gene that encodes for the compound of interest is isolated.

"The problem is supply," he explains. Many companies receive licenses for compounds from the sea but stall when they realize that they can't get enough from harvesting whole macro-organisms, like sea slugs or sponges. Especially for a disease like malaria, the drug company can't afford to spend that much money making the compound because they need to keep the cost of the drug low. They need a more economical source.

"There are lots of exciting compounds out there, but few have made it to market," Hill continues. In fact, only a single drug of oceanic origin has been approved by the Food and Drug Administration — a small peptide from a cone shell mollusk that can be used to treat severe pain.

Hill's success in isolating these two drug-producing microbes from their host, one of the first times this has been accomplished, may open a new chapter in development of drugs from the deep. Working in constant collaboration with Mark Hamann, a marine natural products chemist from the University of Mississippi, he continues to look towards bacteria as the pharmaceutical jackpot of the undersea world. He's focusing closely on sponges now, which are filled with bacterial cells — in some cases 50 percent of their weight comes from their microbial inhabitants. Many sponges have over 200-300 different compounds associated with them, mainly to prevent algae from growing or fish from feeding on them.

Most of the symbionts in sponges are novel and have not yet been grown in culture. For the most part, no one yet knows which symbionts are producing which compounds or even which compounds might have important pharmaceutical powers. But Hill is on the case.

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