Need a new antibiotic? Set the bacteria against each other!
Scientists at the Massachusetts Institute of Technology and the University of Florida have proposed a new method for creating antibiotics, which consists in "inciting" one type of bacteria against another.
The problem of antibiotic-resistant bacterial strains is becoming increasingly urgent for medical institutions around the world, whose patients are increasingly suffering from intractable hospital infections. Scientists around the world are busy developing new antibiotics. One of the directions of the search is to combine existing drugs in order to obtain more effective compounds. At the same time, attempts to create drugs that selectively act on specific mechanisms are more popular. The results of recent work on sequencing bacterial genomes indicate that the bacteria themselves are an inexhaustible source of new antibiotics unknown to specialists, the synthesis of which does not occur in normal laboratory conditions, where bacteria do not have to compete for food resources.
When sequencing the genome of the soil bacteria Rhodococcus fascians, the authors unexpectedly found in the genome of these bacteria a number of genes involved in the metabolism of antibiotic-like compounds.
These results indicated the ability of R.fascians to synthesize antibiotics, but this was not observed in laboratory conditions until they were placed in culture together with Streptomyces padanus – producers of the antibiotic neomycin, which is part of many antibacterial creams (the genus streptomyces is one of the most famous manufacturers of antibiotics in the microcosm).
In a competitive environment, one of the studied strains of R.fascians began to synthesize compounds exhibiting antibiotic activity to a wide range of gram-positive and gram-negative bacteria.
These substances, called rhodostreptomycins, belong to the same class of aminoglycosides as neomycin and streptomycin used to treat tuberculosis.
It is not yet known whether the new compounds are suitable for clinical use, but experiments have shown that they effectively destroy the "Nobel" bacteria associated with gastritis and gastric ulcer Helicobacter pylori and do not break down under conditions of high acidity (for example, in the presence of gastric juice). In addition, the rhodostreptomycin molecule contains a previously unknown structural component that may be useful in the development of new drugs.
The authors found a large DNA fragment belonging to S.padanus in the genome of the R.fascians strain synthesizing rhodostreptomycin. The exchange of DNA fragments is considered a common technique in the bacterial world, which underlies the ability of microorganisms to quickly acquire resistance to antibiotics. In this case, scientists were able to see the immediate result of this mechanism. However, to date, scientists have sequenced only half of the "alien" DNA in the genome of R.fascians and cannot say with certainty whether it contains genes responsible for the synthesis of rhodostreptomycin, or triggers its own mechanisms of synthesis that are in a suppressed state.
The results of the work aroused great interest among specialists engaged in the search for new antibiotics, since the approach proposed by the authors can be used to identify the latent abilities of various bacteria to produce antibacterial drugs.
Article by Kazuhiko Kurosawa et al. Rhodostreptomycins, Antibiotics Biosynthesized Following Horizontal Gene Transfer from Streptomyces padanus to Rhodococcus fascians is published in the January issue of J.Am.Chem.Soc.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of TechnologyReview
20.03.2008