Scientists searching for natural compounds to
control fungi in plants may have stumbled onto new antibiotics that control
Streptococcus and Staphylococcus bacteria.
Agricultural Research Service
scientists at Lane, Okla., and College Station, Texas, say they have discovered
a new family of antibiotic compounds--not related to penicillin--with potent
antimicrobial activity. They made their find while looking for microbial
compounds to control diseases like root rot of muskmelon and watermelon plants.
The discovery and use of antibiotics like penicillin against infectious
disease have added about 20 years to the average human life expectancy in
developed countries. However, today, up to 80 percent of all strains of
Staphylococcus are resistant to penicillin and its derivative forms.
Similar resistance to penicillin and other antibiotics has been observed in
other bacterial pathogens, like Streptococcus.
The scientists have isolated six compounds that they say exhibit some degree
of antibiotic activity against a broad spectrum of gram-negative and/or
gram-positive bacteria of concern to both agricultural and health
professionals. The compounds varied in their selectivity and ability to retard
growth or kill important bacterial pathogens.
The chemical makeup of the cell wall--one of the several techniques used to
classify bacteria--determines whether a bacteria is gram-positive or
gram-negative. Agrobacterium, Erwinia and Pseudomonas are
gram-negative bacteria. Bacillus, Micrococcus, Staphylococcus and
Streptococcus are gram-positive bacteria.
Three of the compounds exhibited excellent activity against the genera
Staphylococcus and Streptococcus that cause diseases in humans.
The scientists say one of the six compounds exhibited strong antibiotic
activity against all seven bacterial species tested. Just 10 micrograms per
milliliter totally repressed growth of or killed species of gram-positive
bacteria within the genera Micrococcus, Streptococcus, Staphylococcus
As pathogens develop resistance, new and different antibiotics must be found
to replace those currently available. The scientists say that some of their
compounds may be as good as or better than commercial antibiotics at resisting
bacterial infections and could be of considerable interest to the
pharmaceutical industry. ARS is the chief research arm of
Scientific contact: Benny Bruton, ARS
South Central Agricultural
Research Laboratory, Lane, Okla., phone (580) 889-7395, fax (580) 889-5783,