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July 7, 2019  |  

Comparative genomics of Beauveria bassiana: uncovering signatures of virulence against mosquitoes.

Entomopathogenic fungi such as Beauveria bassiana are promising biological agents for control of malaria mosquitoes. Indeed, infection with B. bassiana reduces the lifespan of mosquitoes in the laboratory and in the field. Natural isolates of B. bassiana show up to 10-fold differences in virulence between the most and the least virulent isolate. In this study, we sequenced the genomes of five isolates representing the extremes of low/high virulence and three RNA libraries, and applied a genome comparison approach to uncover genetic mechanisms underpinning virulence.A high-quality, near-complete genome assembly was achieved for the highly virulent isolate Bb8028, which was compared to the assemblies of the four other isolates. Whole genome analysis showed a high level of genetic diversity between the five isolates (2.85-16.8 SNPs/kb), which grouped into two distinct phylogenetic clusters. Mating type gene analysis revealed the presence of either the MAT1-1-1 or the MAT1-2-1 gene. Moreover, a putative new MAT gene (MAT1-2-8) was detected in the MAT1-2 locus. Comparative genome analysis revealed that Bb8028 contains 163 genes exclusive for this isolate. These unique genes have a tendency to cluster in the genome and to be often located near the telomeres. Among the genes unique to Bb8028 are a Non-Ribosomal Peptide Synthetase (NRPS) secondary metabolite gene cluster, a polyketide synthase (PKS) gene, and five genes with homology to bacterial toxins. A survey of candidate virulence genes for B. bassiana is presented.Our results indicate several genes and molecular processes that may underpin virulence towards mosquitoes. Thus, the genome sequences of five isolates of B. bassiana provide a better understanding of the natural variation in virulence and will offer a major resource for future research on this important biological control agent.


July 7, 2019  |  

Genomics-inspired discovery of three antibacterial active metabolites, aurantinins B, C, and D from compost-associated Bacillus subtilis fmb60.

Fmb60 is a wild-type Bacillus subtilis isolated from compost with significant broad-spectrum antimicrobial activities. Two novel PKS clusters were recognized in the genome sequence of fmb60, and then three polyene antibiotics, aurantinins B, C, and D, 1-3, were obtained by bioactivity-guided isolation from the fermentation of fmb60. The structures of aurantinins B-D were elucidated by LC-HRMS and NMR data analysis. Aurantinins C and D were identified as new antimicrobial compounds. The three aurantinins showed significant activity against multidrug-resistant Staphylococcus aureus and Clostridium sporogenes. However, aurantinins B-D did not exhibit any cytotoxicity (IC50 > 100 µg/mL) against LO2 and Caco2 cell lines by MTT assay. Furthermore, using S. aureus as a model bacterium to explore the antibacterial mechanism of aurantinins B-D, it was revealed that the bactericidal activity of aurantinins B-D was related to their ability to disrupt the cell membrane.


July 7, 2019  |  

Complete genome sequence of Streptomyces formicae KY5, the formicamycin producer.

Here we report the complete genome of the new species Streptomyces formicae KY5 isolated from Tetraponera fungus growing ants. S. formicae was sequenced using the PacBio and 454 platforms to generate a single linear chromosome with terminal inverted repeats. Illumina MiSeq sequencing was used to correct base changes resulting from the high error rate associated with PacBio. The genome is 9.6 Mbps, has a GC content of 71.38% and contains 8162 protein coding sequences. Predictive analysis shows this strain encodes at least 45 gene clusters for the biosynthesis of secondary metabolites, including a type 2 polyketide synthase encoding cluster for the antibacterial formicamycins. Streptomyces formicae KY5 is a new, taxonomically distinct Streptomyces species and this complete genome sequence provides an important marker in the genus of Streptomyces. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.


July 7, 2019  |  

Complete genome sequence of Flavobacterium kingsejongi WV39, a type species of the genus Flavobacterium and a microbial C40 carotenoid zeaxanthin producer.

A novel species, Flavobacterium kingsejongi WV39, isolated from feces of Antarctic penguins and a type species of the genus Flavobacterium, is yellow because it synthesizes a C40 carotenoid zeaxanthin. The complete genome of F. kingsejongi WV39 is made up of a single circular chromosome (4,224,053bp, 39.8% G+C content). Annotation analysis revealed 3,955 coding sequences, 72 RNAs (18 rRNA+54 tRNA), and five genes involved in zeaxanthin biosynthesis. The key gene encoding ß-carotenoid hydroxylase (CrtZ), which is the last enzyme in the zeaxanthin biosynthetic pathway, was cloned and subjected to complementary analysis in a heterologous E. coli strain. The CrtZ of F. kingsejongi WV39 showed a higher activity than other reported CrtZs. Copyright © 2017 Elsevier B.V. All rights reserved.


July 7, 2019  |  

The ‘gifted’ actinomycete Streptomyces leeuwenhoekii.

Streptomyces leeuwenhoekii strains C34T, C38, C58 and C79 were isolated from a soil sample collected from the Chaxa Lagoon, located in the Salar de Atacama in northern Chile. These streptomycetes produce a variety of new specialised metabolites with antibiotic, anti-cancer and anti-inflammatory activities. Moreover, genome mining performed on two of these strains has revealed the presence of biosynthetic gene clusters with the potential to produce new specialised metabolites. This review focusses on this new clade of Streptomyces strains, summarises the literature and presents new information on strain C34T.


July 7, 2019  |  

Complete genome sequence of the marine Rhodococcus sp. H-CA8f isolated from Comau fjord in Northern Patagonia, Chile

Rhodococcus sp. H-CA8f was isolated from marine sediments obtained from the Comau fjord, located in Northern Chilean Patagonia. Whole-genome sequencing was achieved using PacBio RS II platform, comprising one closed, complete chromosome of 6,19?Mbp with a 62.45% G?+?C content. The chromosome harbours several metabolic pathways providing a wide catabolic potential, where the upper biphenyl route is described. Also, Rhodococcus sp. H-CA8f bears one linear mega-plasmid of 301?Kbp and 62.34% of G?+?C content, where genomic analyses demonstrated that it is constituted mostly by putative ORFs with unknown functions, representing a novel genetic feature. These genetic characteristics provide relevant insights regarding Chilean marine actinobacterial strains.


July 7, 2019  |  

Synthetic biology, genome mining, and combinatorial biosynthesis of NRPS-derived antibiotics: a perspective.

Combinatorial biosynthesis of novel secondary metabolites derived from nonribosomal peptide synthetases (NRPSs) has been in slow development for about a quarter of a century. Progress has been hampered by the complexity of the giant multimodular multienzymes. More recently, advances have been made on understanding the chemical and structural biology of these complex megaenzymes, and on learning the design rules for engineering functional hybrid enzymes. In this perspective, I address what has been learned about successful engineering of complex lipopeptides related to daptomycin, and discuss how synthetic biology and microbial genome mining can converge to broaden the scope and enhance the speed and robustness of combinatorial biosynthesis of NRPS-derived natural products for drug discovery.


July 7, 2019  |  

To B or not to B: a tale of unorthodox chromosomes.

Highlights • B chromosomes are dispensable parts of the karyotype of many eukaryotes. • Deemed genome parasites in plants and animals, provide advantage to pathogenic fungi. • Often enriched in repeats and in fast evolving pathogenicity-related genes. • B chromosomes are not a uniform class, share certain features with core chromosomes.


July 7, 2019  |  

Complete genome sequence of Microcystis aeruginosa NIES-2481 and common genomic features of group G M. aeruginosa.

Microcystis aeruginosa is a freshwater bloom-forming cyanobacterium that is distributed worldwide. M. aeruginosa can be divided into at least 8 phylogenetic groups (A-G and X) at the intraspecific level. Here, we report the complete genome sequence of M. aeruginosa NIES-2481, which was isolated from Lake Kasumigaura, Japan, and is assigned to group G. The complete genome sequence of M. aeruginosa NIES-2481 comprises a 4.29-Mbp circular chromosome and a 147,539-bp plasmid; the circular chromosome and the plasmid contain 4,332 and 167 protein-coding genes, respectively. Comparative analysis with the complete genome of M. aeruginosa NIES-2549, which belongs to the same group with NIES-2481, showed that the genome size is the smallest level in previously sequenced M. aeruginosa strains, and the genomes do not contain a microcystin biosynthetic gene cluster in common. Synteny analysis revealed only small-scale rearrangements between the two genomes.


July 7, 2019  |  

Draft genome sequence of Paucibacter aquatile CR182T, a strain with antimicrobial activity isolated from freshwater of Nakdong River in South Korea.

This report details a draft genome sequence of Paucibacter aquatile CR182T, isolated from river water, which contains 5,523,543?bp, has a G+C content of 66.3%, and harbors 4,544 protein-coding genes in 4 contigs. These genome data provide insights into the genetic basis of this strain’s antibacterial activity and adaptive mechanisms. Copyright © 2018 Chung et al.


July 7, 2019  |  

Draft genome sequence of Bacillus velezensis Lzh-a42, a plant growth- promoting rhizobacterium isolated from tomato rhizosphere.

The plant growth-promoting rhizobacterium Bacillus velezensis strain Lzh-a42, which has antimicrobial activity, was isolated from tomato rhizosphere. Here, we report its genome sequence, which includes several predicted functional genes related to secondary metabolite biosynthesis, antimicrobial activity, and biofilm synthesis. Copyright © 2018 Li et al.


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