The researchers isolated the antibiotic, dubbed it rhodostreptomycin, and started testing it to see what else it would kill. It proved effective against many other strains of bacteria, most notably Helicobacter pylori. Rhodostreptomycin is a promising candidate to treat H. pylori because it can survive in very acidic environments such as the stomach.
The antibiotic turned out to be a type of molecule called an aminoglycoside, composed of peculiar sugars, one of which has a ring structure that has not been seen before. The ring structure could offer chemists a new target for modification, allowing them to synthesize antibiotics that are more effective and/or stable.
Even if (rhodostreptomycin) is not the best antibiotic, it provides new structures to make chemical derivatives of, said Lessard. This may be a starting point for new antibiotics.
One mystery still to be solved is why Rhodococcus started producing this antibiotic. One theory is that the presence of the competing strain of bacteria caused Rhodococcus to raise the alarm and turn on new genes.
The version of Rhodococcus that produces the antibiotic has a megaplasmid, or large segment of extra DNA, that it received from Streptomyces. A logical conclusion is that the plasmid carries the gene for rhodostreptomycin, but the researchers have sequenced more than half of the plasmid and found no genes that correlate to the antibiotic.
Another theory is that the plasmid itself served as the insult that provoked Rhodococcus into producing the antibiotic. Alternatively, it is possible that some kind of interaction of the two bacterial genomes produced the new antibiotic.
Somehow the genes in the megaplasmid combined with the genes in Rhodococcus and together they produced something that neither parent could make alone, said Lessard.
If scientists could figure out how that happens, they could start to manipulate bacterial genomes in
|Contact: Elizabeth Thomson|
Massachusetts Institute of Technology