July 7, 2019  |  

The draft genome of the lichen-forming fungus Lasallia hispanica (Frey) Sancho & A. Crespo

Lasallia hispanica (Frey) Sancho & A. Crespo is one of three Lasallia species occurring in central-western Europe. It is an orophytic, photophilous Mediterranean endemic which is sympatric with the closely related, widely distributed, highly clonal sister taxon L. pustulata in the supra- and oro-Mediterranean belts. We sequenced the genome of L. hispanica from a multispore isolate. The total genome length is 41·2 Mb, including 8488 gene models. We present the annotation of a variety of genes that are involved in protein secretion, mating processes and secondary metabolism, and we report transposable elements. Additionally, we compared the genome of L. hispanica to the closely related, yet ecologically distant, L. pustulata and found high synteny in gene content and order. The newly assembled and annotated L. hispanica genome represents a useful resource for future investigations into niche differentiation, speciation and microevolution in L. hispanica and other members of the genus.

July 7, 2019  |  

Auroramycin, a potent antibiotic from Streptomyces roseosporus by CRISPR-Cas9 activation.

Silent biosynthetic gene clusters represent a potentially rich source for new bioactive compounds. We report the discovery, characterization and biosynthesis of a novel doubly glycosylated 24-membered polyene macrolactam from a silent biosynthetic gene cluster in Streptomyces roseosporus using the CRISPR-Cas9 gene cluster activation strategy. Structural characterization of this polyketide, named auroramycin, revealed a rare isobutyrylmalonyl extender unit and a unique pair of aminosugars. Relative and absolute stereochemistry were determined using a combination of spectroscopic analyses, chemical derivatization, and computational analysis. The activated gene cluster for auroramycin production was also verified by transcriptional analyses and gene deletions. Finally, auroramycin exhibited potent anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activity towards clinical drug-resistant isolates.© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

July 7, 2019  |  

Complete genome of Micromonospora sp. strain B006 reveals biosynthetic potential of a Lake Michigan Actinomycete.

Actinomycete bacteria isolated from freshwater environments are an unexplored source of natural products. Here we report the complete genome of the Great Lakes-derived Micromonospora sp. strain B006, revealing its potential for natural product biosynthesis. The 7-megabase pair chromosome of strain B006 was sequenced using Illumina and Oxford Nanopore technologies followed by Sanger sequencing to close remaining gaps. All identified biosynthetic gene clusters (BGCs) were manually curated. Five known BGCs were identified encoding desferrioxamine, alkyl- O-dihydrogeranylmethoxyhydroquinone, a spore pigment, sioxanthin, and diazepinomicin, which is currently in phase II clinical trials to treat Phelan-McDermid syndrome and co-morbid epilepsy. We report here that strain B006 is indeed a producer of diazepinomicin and at yields higher than previously reported. Moreover, 11 of the 16 identified BGCs are orphan, eight of which were transcriptionally active under the culture condition tested. Orphan BGCs include an enediyne polyketide synthase and an uncharacteristically large, 36-module polyketide synthase-nonribosomal peptide synthetase BGC. We developed a genetics system for Micromonospora sp. B006 that will contribute to deorphaning BGCs in the future. This study is one of the few attempts to report the biosynthetic capacity of a freshwater-derived actinomycete and highlights this resource as a potential reservoir for new natural products.

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.

July 7, 2019  |  

Genome analysis of Vallitalea guaymasensis strain L81 isolated from a deep-sea hydrothermal vent system.

Abyssivirga alkaniphila strain L81T, recently isolated from a black smoker biofilm at the Loki’s Castle hydrothermal vent field, was previously described as a mesophilic, obligately anaerobic heterotroph able to ferment carbohydrates, peptides, and aliphatic hydrocarbons. The strain was classified as a new genus within the family Lachnospiraceae. Herein, its genome is analyzed and A. alkaniphila is reassigned to the genus Vallitalea as a new strain of V. guaymasensis, designated V. guaymasensis strain L81. The 6.4 Mbp genome contained 5651 protein encoding genes, whereof 4043 were given a functional prediction. Pathways for fermentation of mono-saccharides, di-saccharides, peptides, and amino acids were identified whereas a complete pathway for the fermentation of n-alkanes was not found. Growth on carbohydrates and proteinous compounds supported methane production in co-cultures with Methanoplanus limicola. Multiple confurcating hydrogen-producing hydrogenases, a putative bifurcating electron-transferring flavoprotein—butyryl-CoA dehydrogenase complex, and a Rnf-complex form a basis for the observed hydrogen-production and a putative reverse electron-transport in V. guaymasensis strain L81. Combined with the observation that n-alkanes did not support growth in co-cultures with M. limicola, it seemed more plausible that the previously observed degradation patterns of crude-oil in strain L81 are explained by unspecific activation and may represent a detoxification mechanism, representing an interesting ecological function. Genes encoding a capacity for polyketide synthesis, prophages, and resistance to antibiotics shows interactions with the co-occurring microorganisms. This study enlightens the function of the fermentative microorganisms from hydrothermal vents systems and adds valuable information on the bioprospecting potential emerging in deep-sea hydrothermal systems.

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