Bacterial battle for survival leads to new antibiotic

February 29th, 2008 - 12:35 am ICT by admin  


Washington, Feb 28 (IANS) A bacteria under threat from another produced a new type of antibiotic, which can help in the treatment of stomach ulcers. Helicobacter pylori, the bacteria that causes stomach ulcers, may be more amenable to treatment after MIT biologists provoked soil-dwelling bacteria into producing the new type of antibiotic.

A combination of luck, patience and deft detective work contributed to the discovery of the new antibiotic, according to Philip Lessard, research scientist in Anthony Sinskey’s laboratory at the Massachusetts Institute of Technology.

Sinskey’s lab has been studying Rhodococcus, a type of soil-dwelling bacteria. While sequencing the genome of one Rhodococcus species, researchers noticed that a large number of genes seemed to code for secondary metabolic products, which are compounds such as antibiotics, toxins and pigments.

However, Rhodococcus does not normally produce antibiotics. Many bacteria have genes for antibiotics that are only activated when the bacteria are threatened in some way, so the researchers suspected that might be true of Rhodococcus.

Kazuhiko Kurosawa, a postdoctoral associate in the MIT, decided to try to provoke the bacteria into synthesizing antibiotics by placing them in stressful environments. He forced them to grow in the presence of a competing bacteria, a strain of streptomyces.

Streptomyces produces an antibiotic that normally kills other bacteria, but in one of the experimental test tubes, Rhodococcus started producing its own antibiotic, which wiped out the streptomyces.

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.

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 study has been published in the February issue of the Journal of the American Chemical Society.

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