Reporter gene method for identifying the target of a novel antibiotic. The agar plate has been covered with B. subtilis bacteria bearing a reporter gene that generates a blue colour when the cells sense a particular kind of antibiotic stress. The small round plugs are actinomycete samples. Ones that produce antibiotics generate a zone of killing of the B. subtilis, and at the edge of the killing zone surviving bacteria generate a blue “halo”.
Industrial significance
Amongst bacteria, members of the phylum Actinobacteria, notably the genus Streptomyces, are a unique source of new natural products, especially clinical useful antibiotics, antimetabolites and anticancer agents.
Indeed, actinomycetes account for nearly half of all known microbial natural products with about 80% of these compounds (ca. 3000) being produced by streptomycetes. Despite this remarkable metabolic diversity, it has been estimated that only about 10% of the total number of natural products that can be synthesized by these organisms have been discovered.
Actinoplanes, Amycolatopsis and Micromonospora strains are also a source of clinically significant antibiotics whereas members of less well known genera, such as Dermacoccus and Verrucosispora, are a potentially rich source of novel natural products. It seems likely that such organisms will be a continuing source of new natural products as whole-genome sequences of members of these genera are known to have many biosynthetic gene clusters for the production of known or predicted bioactive compounds, notably antibiotics.
