Effects of bkdAB interruption on avermectin biosynthesis / 生物工程学报

In this study, Streptomyces avermitilis Bjbm0006 which produces four avermectin B components was used as an original test strain. A replacement plasmid containing a gene cluster bkdAB (branched-chain alpha-keto acid dehydrogenase gene) involved in the biosynthesis of avermectin B in S. avermitilis Bjbm0006 was constructed by means of PCR technique and then named as pHJ5821 (pHZ1358::bkdAB&erm). A recombinant strain Bjbm5821 was obtained after the gene cluster was interrupted by double crossover. This strain was tested in laboratory conditions and analysed by PCR using the total DNA as template. The HPLC analysis showed that the strain Bjbm5821 synthesized the same 'a' components Bla and B2a as the original strain did. However, It lost the ability for the production of 'b'components for example B1b and B2b. A novel compound was detected in fermentation products. The results of present study suggests that the production of gene cluster bkdAB may play a main role similar to alpha-ketoisovaleric acid dehydrogenase in the pathway of avermectin synthesis.

Research Advance on Marinomonas / 微生物学通报

In this mini review,some research advance on Marinomonas from domestic and overseas was briefly summarized,mainly including of its classification、ecological distribution、functional genes and bioactive molecules.Furthermore,some suggestion and perspectives for further studies on Marinomonas were also proposed.

Identification of a Marine Bacterium Strain and Characterization of a Novel Functional Gene Cluster Involved in Melanin Biosynthesis / 微生物学通报

A marine bacterium MWYL1,originally isolated from the roots of Spartina anglica growing in a salt marsh near seaside,was identified as a member of the genus of Marinomonas via morphology characterization、physiological test and 16S rDNA sequencing and Blast analysis.The strain was short,rod,gram-negative,grew aerobically and optimally at 28℃.The analysis of 16S rDNA sequence suggests that the sequence similarity values are 97% and 95% with Marinomonas pontica and Marinomonas dokdonensis,respectively.One fosmid clone producing melanin was directly isolated by plating from the genomic library of Marinomonas MWYL1.The novel functional gene cluster involved in melanin biosynthesis was screened after subcloning and sequencing of the 14kb insert in pUC18,further more,the putative functional genes was preminary analyzed using bioinformatics.