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Genomic analysis of the clavulanic acid (CA)-high-producing Streptomyces clavuligerus strains, OL13 and OR, developed through random mutagenesis revealed a frameshift mutation in the cas1 gene-encoding clavaminate synthase 1. Overexpression of the intact cas1 in S. clavuligerus OR enhanced the CA titer by approximately 25%, producing ~ 4.95 g/L of CA, over the OR strain in the flask culture. Moreover, overexpression of the pathway-specific positive regulatory genes, ccaR and claR, in the OR strain improved CA yield by approximately 43% (~ 5.66 g/L) in the flask. However, co-expression of the intact cas1 with ccaR-claR did not further improve CA production. In the 7 L fermenter culture, maximum CA production by the OR strain expressing the wild-type cas1 and ccaR-claR reached approximately 5.52 g/L and 6.01 g/L, respectively, demonstrating that reverse engineering or simple rational metabolic engineering is an efficient method for further improvement of industrial strains.

Anthracyclines, such as doxorubicin, are effective anticancer drugs composed of a tetracyclic polyketide aglycone and one or more deoxysugar moieties, which play a critical role in their biological activity. A facile one-pot combinatorial biosynthetic system was developed for the generation of a range of glycosylated derivatives of anthracyclines. Cocultivation of Streptomyces venezuelae mutants producing two anthracycline aglycones with eight different nucleotide deoxysugar-producing S. venezuelae mutants that coexpress a substrate-flexible glycosyltransferase led to the generation of 16 aklavinone or ε-rhodomycinone glycosides containing diverse deoxysugar moieties, seven of which are new. This demonstrates the potential of the one-pot combinatorial biosynthetic system based on cocultivation as a facile biological tool capable of combining diverse aglycones and deoxysugars to generate structurally diverse polyketides carrying engineered sugars for drug discovery and development.

Geosmin and 2-methylisoborneol (2-MIB) are organic compounds known to cause earthy and musty odors in drinking water. In Korea, during the summer of 2012, a geosmin outbreak in the drinking water supply prompted further research to identify the source of the odorous materials, since these occurrences were not well understood or monitored. The purpose of this study was to investigate how important a role actinomycetes play in the production of geosmin and 2-MIB in Paldang Lake by measurement of microbial density (the number of colony-forming units), pyrosequencing of 16S rRNA genes, and determination of the prevalence of the geosmin synthase gene. Three sampling sites (P1, P2, and P3) were selected. The increase in geosmin concentration was paralleled by an increase in actinomycetes (Streptomyces spp.) and cyanobacteria (Anabaena spp.) populations. The bacterial communities in Paldang Lake were characterized by 454 pyrosequencing based on 16S rRNA gene sequences. P1 (North Han River) showed the hig...

The performance of multi-level DPSK modulation formats is investigated. The results include the relationship between the nonlinear impairments and number of signal levels, and the performance degradation due to linear cross-talk between the WDM channels.