Marine plant uses chemical wafare to fight microbes

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Seaweed Surprise: Marine Plant Uses Chemical Warfare To Fight Microbes

 

Scientists have discovered that seaweeds defend themselves from specific

pathogens with naturally occurring antibiotics. The finding helps explain

why some seaweeds, sponges and corals appear to avoid most infections by

fungi and bacteria, according to a study published May 19 in the Proceedings

of the National Academy of Sciences. ³Seaweeds live in constant contact with

potentially dangerous microbes, and they have apparently evolved a chemical

defense to help resist disease,² said lead author Julia Kubanek, an

assistant professor of biology and chemistry at the Georgia Institute of

Technology in Atlanta. ³These plants have a really effective way of

defending themselves.²

 

Few studies have addressed disease resistance in seaweeds, and seaweed

diseases are little understood, except for species that are commercially

important ­ for example, the seaweed used for sushi. This study¹s report of

isolating a potent antifungal compound contained in the common seaweed

species Lobophora variegata reveals an unusual chemical structure not seen

before in plants.

 

And the study lends insight into the ecological interactions between this

seaweed species and other marine organisms, Kubanek said. Also, it presents

the possibility of biomedical applications for the newly discovered

antifungal compound, she added.

 

The research ­ funded in part by the National Science Foundation ­ was

conducted in collaboration with colleagues Paul Jensen and William Fenical

at the Scripps Institution of Oceanography in San Diego, Calif., Paul Keifer

of Varian Inc. in Palo Alto, Calif., and researchers M. Cameron Sullards and

Dwight Collins of Georgia Tech.

 

³Based on the antimicrobial activities we detected in a large survey of many

different algal species, it is possible that antimicrobial chemical defenses

are more common than previously believed and that L. variegata may be one of

many species that use natural antibiotics to defend against infection,²

Jensen said.

 

Jensen devised a bioassay to measure the antimicrobial potential of a common

seaweed species, Lobophora variegata. He combined biological extracts from

seaweed harvested in the Bahamas with a fungus or bacterium and monitored

the sample to see if the microbes grew. Of the 51 samples tested, 46

exhibited extraordinarily potent antifungal activity that could be traced to

exceedingly low concentrations of an antifungal compound in the seaweed.

Suppressed growth of microbes in the samples suggests that a natural

antimicrobial compound is at work, Kubanek explained.

 

³We have discovered a new antibiotic with a complex chemical structure that

structurally resembles two groups of macrolide antibiotics (i.e., those that

kill fungi) -- one found in marine sponges and the other in blue-green

algae,² Kubanek said. Because of the tiny available quantities of this new

compound, researchers have not applied for a patent yet.

 

The pharmaceutical company Bristol-Myers Squibb and a San Diego

biotechnology company, Nereus Pharmaceuticals Inc., are partners with

Scripps and are collaborating on related ongoing research. Scientists still

need to determine whether the seaweed is actually the original source of the

antibiotic, Kubanek added. The antimicrobial compound could be the byproduct

of symbiosis between the seaweed and an as-yet unidentified microbe. If this

is the case, it would be one of the rare examples of such a chemical defense

for plants and animals, researchers reported.

 

They believe that further investigations of chemically mediated interactions

between marine microbes and larger organisms are likely to reveal new

molecules and mechanisms that enable marine plants and animals to persist

despite intense microbial challenges, researchers wrote.

 

http://gtresearchnews.gatech.edu/newsrelease/seaweed.htm