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The analysis of an arsenic resistance (ars) gene cluster from a large linear plasmid, pHZ227, in Streptomyces sp. strain FR-008 is reported and the determinant is compared with the putative ars gene clusters from Streptomyces coelicolor A3(2) (1) and Streptomyces sp. strain F2. The pHZ227 ArsB protein has showed homology to the yeast arsenite transporter Acr3p and the pHZ227 ArsC is a bacterial thioredoxin-dpendent ArsC-type arsenate reductase with four conserved cysteine thioreduction-requiring motifs.

The mapping of the chromosomal DNA of Streptomyces hygroscopicus 10-22 reveals a linear organization with terminal proteins and large terminal inverted repeats as shown by overlapping chromosomal deletion technique and pulsed-field gel electrophoresis.

Research has been conducted on the gene clusters containing type I polyketide synthase genes. The isolation of these clusters from 'Streptomyces nanchangensis' which produces meilingmycin and nanchangmycin has been carried out and the results indicate that one of the clusters is involved in the nanchangmycin production.

A new strategy of acyltransferase-ketoreductase didomain PCR amplification was applied to localize the undefined PKS genes encoding the loading and the first two elongation steps for meilingmycin biosynthesis. The study provides a more specific strategy for the cloning of modular type PKS gene clusters.

A study related to the gene fscTE, encoding a putative type II thioesterase (TEII) associated with the FR-008/candicidin gene cluster, is reported. The substrate specificity of fscTE gene is confirmed by its overexpression of fscTE under the strong constitutive ermE*p promoter in the wild-type strain, which did not suppress FR-008/candicidin formation.

A cluster of five genes called dndA in Streptomyces lividans was found to encode a DNA modification system, leading to formation of mutant forms of the sulfur bacterium. The crystallization and spectroscopic analysis outline the role of DndA and DndC in site-specific DNA modification.

A gene cluster responsible for the biosynthesis of validamycin (Val), an aminocyclitol antibiotic widely used as a control agent for sheath blight disease of rice plants, was identified from Streptomyces hygroscopicus subsp. jinggangensis 5008. The direct involvement of valA, in validamycin biosynthesis was confirmed in vivo by gene inactivation as well as in vitro by biochemical characterization of the reaction catalyzed by the ValA protein heterologously overexpressed in Escherichia coli.

A detailed analysis of Streptomyces lividans ZX1, which turns out to be a pleiotropic mutant with a large chromosomal delection of ca. 90 kb, whose delection junctions in the wild-type strain 66 and the deletion and fused sequence in strain ZX1 are localized and characterized. Comparison of s. lividans ZX1 and its progenitor 66 reveals that the ca. 90-kb deletion in strain ZX1 may have originated from an insertion from an unknown source.

Research has been conducted on Micromonospora sp. strain 40027 which produces antibiotic fortimicin A. The authors discuss the development of the vector system used for the site-specific or autonomous integrative gene cloning for this strain.