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Type I polyketide synthases (PKSs) are multifunctional enzymes that are organized into modules, each of which minimally contains a [beta]-ketoacyl synthase, an acyltransferase (AT), and an acyl carrier protein. Here we report that the leinamycin (LNM) biosynthetic gene cluster from Streptomyces atroolivaceus S-140 consists of two PKS genes, InmI and InmJ, that encode six PKS modules, none of which contain the cognate AT domain. The only AT activity identified within the Inm gene cluster is a discrete AT protein encoded by InmG. Inactivation of InmG, InmI, or InmJ in vivo abolished LNM biosynthesis. Biochemical characterization of LnmG in vitro showed that it efficiently and specifically loaded malonyl CoA to all six PKS modules. These findings unveiled a previously unknown PKS architecture that is characterized by a discrete, iteratively acting AT protein that loads the extender units in trans to 'AT-less' multifunctional type I PKS proteins for polyketide biosynthesis. This PKS structure provides opportunities for PKS engineering as exemplified by overexpressing InmG to improve LNM production.

Research has been conducted on produced by Streptomyces atroolivaceus S-140 leinamycin. The study of leinamycin biosynthesis has been performed, and the generation of new leinamycin analogues produced via the use of combinatorial biosynthesis is described.

Results reveal that TOXF gene has a role in the HC-toxin production and pathogenicity of Cochliobolus carbonum. The amino acid sequence data show homology to branched-chain-amino-acid transaminases from other species.

Research was conducted to examine the targeted mutants of Cochliobolus carbonum lacking the two major extracellular polygalacturonases (exoPG). The purification of the exoPG activity of C carbonum and the cloning of its gene, PGX1, was also performed. Double pgn1/pgx1 mutant strain was developed by crossing. The continued growth of the pgn1/pgx1 mutant strain on pectin could be attributed to one or more of PG residual activities.