Sea Bacterium Compound May Help Fight Cancer

The team published a paper on its findings in the May 25 issue of “Chemistry and Biology.”
The bacterium — Leptolyngbya crossbyana — forms enormous colonies in the ocean that are visible with the naked eye. 

The team is excited about the discovery of a new class of organic molecules the researchers have named “honaucins.” They are distinguished by the presence of a chlorine atom in a primary position — at the end of a carbon chain. Having a halogen atom at the end of a chain makes these compounds extremely reactive, and extremely unusual.

Researchers in Gerwick’s laboratory conducted a variety of tests used to determine the function of biological molecules.

They determined that honaucins were lethal to many bacteria and could prevent inflammation–a biological process in humans that has been linked to a variety of immune diseases and cancer.

Honaucins are especially unique because they prevent other bacteria from reaching a certain population density, rather than poisoning each bacterium individually.

“They’re called anti-quorum sensing compounds,” Gerwick said. “They represent a completely new mechanism for bacteria control. It’s believed that it won’t give rise to resistance as quickly.”

Gerwick said that the finding was important because the effective lifetimes of current antibiotics are getting shorter and shorter.

“It used to be 10 or 15 years, and now it’s just a few,” he said. “Bacteria nowadays have built up so many resistance mechanisms that they can become resistant at an increased rate.”

According to William Gerwick, a professor both at Scripps and at Skaggs School of Pharmacy and a coauthor of the recently published paper, the Scripps team had a dual purpose in examining the bacteria.

“We certainly wanted to determine how the bacteria were killing the coral reefs,” he said. “But we also wanted to see if we could isolate any potentially useful compounds from the bacteria.”

The scientists believe the bacteria bleach coral reefs by secreting an as-yet unidentified poison.

“We don’t know all the mechanistic details,” Gerwick said. “But we noticed bleaching occurred even where bacteria were absent. That gave us a clue that it might be a toxin that was doing it.”

Leptolyngbya is too new to have a common name, but it is closely related to “Angel’s hair alga” or Cladophora albida. It was first discovered just two years ago, causing irreversible damage to coral off the Kona coast in Hawaii. 

The bacterium is believed to be native to Hawaii and is usually inconspicuous. But in 2009, an enormous bloom, or rapid increase in algal population, caused hundred of miles of coral reef to “bleach” or turn white. Bleaching indicates that the organisms making up a coral reef have died.

“There’s a kind of irony to all this that amazes me,” Gerwick said. “Here’s this organism that’s killing coral, that has within it the capacity to treat a variety of human disease. What is it that they say? One man’s trash is another man’s treasure.” 

The researchers have isolated other compounds from the bacteria, but Gerwick says they have yet to make determinations about their structure and biological activity.

“Some things look really promising. But it’s too early to say anything for certain yet,” he said.

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