April 21, 2020  |  

FadR1, a pathway-specific activator of fidaxomicin biosynthesis in Actinoplanes deccanensis Yp-1.

Fidaxomicin, an 18-membered macrolide antibiotic, is highly active against Clostridium difficile, the most common cause of diarrhea in hospitalized patients. Though the biosynthetic mechanism of fidaxomicin has been well studied, little is known about its regulatory mechanism. Here, we reported that FadR1, a LAL family transcriptional regulator in the fidaxomicin cluster of Actinoplanes deccanensis Yp-1, acts as an activator for fidaxomicin biosynthesis. The disruption of fadR1 abolished the ability to synthesize fidaxomicin, and production could be restored by reintegrating a single copy of fadR1. Overexpression of fadR1 resulted in an approximately 400 % improvement in fidaxomicin production. Electrophoretic mobility shift assays indicated that fidaxomicin biosynthesis is under the control of FadR1 through its binding to the promoter regions of fadM, fadA1-fadP2, fadS2-fadC, and fadE-fadF, respectively. And the conserved binding sites of FadR1 within the four promoter regions were determined by footprinting experiment. All results indicated that fadR1 encodes a pathway-specific positive regulator of fidaxomicin biosynthesis and upregulates the transcription levels of most of genes by binding to the four above intergenic regions. In summary, we not only clearly elucidate the regulatory mechanism of FadR1 but also provide strategies for the construction of industrial high-yield strain of fidaxomicin.

September 22, 2019  |  

Identification of the biosynthetic pathway for the antibiotic bicyclomycin.

Diketopiperazines (DKPs) make up a large group of natural products with diverse structures and biological activities. Bicyclomycin is a broad-spectrum DKP antibiotic with unique structure and function: it contains a highly oxidized bicyclic [4.2.2] ring and is the only known selective inhibitor of the bacterial transcription termination factor, Rho. Here, we identify the biosynthetic gene cluster for bicyclomycin containing six iron-dependent oxidases. We demonstrate that the DKP core is made by a tRNA-dependent cyclodipeptide synthase, and hydroxylations on two unactivated sp(3) carbons are performed by two mononuclear iron, a-ketoglutarate-dependent hydroxylases. Using bioinformatics, we also identify a homologous gene cluster prevalent in a human pathogen Pseudomonas aeruginosa. We detect bicyclomycin by overexpressing this gene cluster and establish P. aeruginosa as a new producer of bicyclomycin. Our work uncovers the biosynthetic pathway for bicyclomycin and sheds light on the intriguing oxidation chemistry that converts a simple DKP into a powerful antibiotic.

September 22, 2019  |  

Heterologous expression guides identification of the biosynthetic gene cluster of chuangxinmycin, an indole alkaloid antibiotic.

The indole alkaloid antibiotic chuangxinmycin, from Actinobacteria Actinoplanes tsinanensis, containing a unique thiopyrano[4,3,2- cd]indole scaffold, is a potent and selective inhibitor of bacterial tryptophanyl-tRNA synthetase. The chuangxinmycin biosynthetic gene cluster was identified by in silico analysis of the genome sequence, then verified by heterologous expression. Systemic gene inactivation and intermediate identification determined the minimum set of genes for unique thiopyrano[4,3,2- cd]indole formation and the concerted action of a radical S-adenosylmethionine protein plus an unknown protein for addition of the 3-methyl group. These findings set a solid foundation for comprehensively investigating the biosynthesis, optimizing yield, and generating new analogues of chuangxinmycin.

July 7, 2019  |  

Paenibacillus ihbetae sp. nov., a cold-adapted antimicrobial producing bacterium isolated from high altitude Suraj Tal Lake in the Indian trans-Himalayas.

The assessment of bacterial diversity and bioprospection of the high-altitude lake Suraj Tal microorganisms for potent antimicrobial activities revealed the presence of two Gram-stain-variable, endospore-forming, rod-shaped, aerobic bacteria, namely IHBB 9852(T) and IHBB 9951. Phylogenetic analysis based on 16S rRNA gene sequence showed the affiliation of strains IHBB 9852(T) and IHBB 9951 within the genus Paenibacillus, exhibiting the highest sequence similarity to Paenibacillus lactis DSM 15596(T) (97.8% and 97.7%) and less than 95.9% similarity to other species of the genus Paenibacillus. DNA-DNA relatedness among strains IHBB 9852(T) and IHBB 9951 was 90.2%, and with P. lactis DSM 15596(T), was 52.7% and 52.4%, respectively. The novel strains contain anteiso-C15:0, iso-C15:0, C16:0 and iso-C16:0 as major fatty acids, and phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol were predominant polar lipids. The DNA G+C content for IHBB 9852T and IHBB 9951 was 52.1 and 52.2mol%. Based on the results of phenotypic and genomic characterisations, we concluded that strains IHBB 9852(T) and IHBB 9951 belong to a novel Paenibacillus species, for which the name Paenibacillus ihbetae sp. nov. is proposed. The type strain is IHBB 9852(T) (=MTCC 12459(T)=MCC 2795(T)=JCM 31131(T)=KACC 19072(T); DPD TaxonNumber TA00046) and IHBB 9951 (=MTCC 12458=MCC 2794=JCM 31132=KACC 19073) is a reference strain. Copyright © 2017. Published by Elsevier GmbH.

July 7, 2019  |  

Complete genome sequence of soil actinobacteria Streptomyces cavourensis TJ430.

A new actinobacteria Streptomyces cavourensis TJ430 was isolated from the mountain soil collected from the southwest of China. In previous study, TJ430 showed striking bactericidal activities and strong ability of antibiotic production. Here, we report complete genome of this bacterium, consisting of 7.6?Mb linear chromosome and 0.2?Mb plasmids. It was predicted 6450 genes in chromosome and 225 genes in plasmids, as well as 12 gene islands in chromosome. Abundant genes have predicted functions in antibiotic metabolism and stress resistance. A whole-genome comparison of S. cavourensis TJ430, S. coelicolor A3(2), and S. lividans 66 indicates that TJ430 has a relatively high degree of strain specificity. The 16S rRNA phylogenetic tree shows the high identities (99.79%) of TJ430 with S. cavourensis DSM40300. TJ430 is a new and rare Streptomyces species, and analysis of its genome helps us to better understand primary metabolism mechanism of this isolate, as well as the evolutionary biology.© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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