Complete Genome Sequence of Actinomadura Parvosata Subsp. Kistnae, A Rich Source of Novel Natural Product (Bio-)Chemistry

Actinomycetes as Producers of Biologically Active Terpenoids: Current Trends and Patents

Terpenes and their derivatives (terpenoids and meroterpenoids, in particular) constitute the largest class of natural compounds, which have valuable biological activities and are promising therapeutic agents. The present review assesses the biosynthetic capabilities of actinomycetes to produce various terpene derivatives; reports the main methodological approaches to searching for new terpenes and their derivatives; identifies the most active terpene producers among actinomycetes; and describes the chemical diversity and biological properties of the obtained compounds. Among terpene derivatives isolated from actinomycetes, compounds with pronounced antifungal, antiviral, antitumor, anti-inflammatory, and other effects were determined. Actinomycete-produced terpenoids and meroterpenoids with high antimicrobial activity are of interest as a source of novel antibiotics effective against drug-resistant pathogenic bacteria. Most of the discovered terpene derivatives are produced by the genus Streptomyces; however, recent publications have reported terpene biosynthesis by members of the genera Actinomadura, Allokutzneria, Amycolatopsis, Kitasatosporia, Micromonospora, Nocardiopsis, Salinispora, Verrucosispora, etc. It should be noted that the use of genetically modified actinomycetes is an effective tool for studying and regulating terpenes, as well as increasing productivity of terpene biosynthesis in comparison with native producers. The review includes research articles on terpene biosynthesis by Actinomycetes between 2000 and 2022, and a patent analysis in this area shows current trends and actual research directions in this field.

Actinomadura decatromicini sp. nov., isolated from mountain soil in Thailand

A novel actinomycete strain CYP1-5T was isolated from the mountain soil sample collected from Chaiyaphum province, Thailand and its taxonomic position was clarified by using a polyphasic taxonomic approach. The chemotaxonomic properties of strain CYP1-5T were consistent within the genus Actinomadura. Cell-wall peptidoglycan of this strain contained meso-diaminopimelic acid. Galactose, madurose, and ribose were presented as the diagnostic sugars in whole-cell hydrolysates. The major menaquinone was MK-9(H6). Major cellular fatty acids were iso-C16:0 and C16:0. Phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, and phosphatidylinositol mannoside were observed as predominant phospholipids. Based on the results of phylogenetic analyses of 16S rRNA gene sequence, strain CYP1-5T was constituent with the genus Actinomadura and was closely related to Actinomadura syzygii GKU157T (99.5%) and Actinomadura chibensis IFM 10266T (= JCM 14158T) (98.2%). The draft genome size of strain CYP1-5T was 9.30 Mb with 72.2 mol% of G + C content. Strain CYP1-5T showed ANIb values of 94.9% with A. syzygii GKU157T and 93.2% with A. chibensis JCM 14158T. Phenotypic characteristics, phylogenetic analysis and genome data support that strain CYP1-5T could be discriminated from its closest relatives, representing a novel species of the genus Actinomadura, for which the name Actinomadura decatromicini sp. nov. is proposed. The type strain is CYP1-5T (= JCM 16996T = KCTC 19916T = TISTR 2901T).

CA, Martin H. C, Mejía LC, Dorrestein PC, Gutiérrez M. Genome Mining, Microbial Interactions, and Molecular Networking Reveals New Dibromoalterochromides from Strains of Pseudoalteromonas of Coiba National Park-Panama

The marine bacterial genus Pseudoalteromonas is known for their ability to produce antimicrobial compounds. The metabolite-producing capacity of Pseudoalteromonas has been associated with strain pigmentation; however, the genomic basis of their antimicrobial capacity remains to be explained. In this study, we sequenced the whole genome of six Pseudoalteromonas strains (three pigmented and three non-pigmented), with the purpose of identifying biosynthetic gene clusters (BGCs) associated to compounds we detected via microbial interactions along through MS-based molecular networking. The genomes were assembled and annotated using the SPAdes and RAST pipelines and mined for the identification of gene clusters involved in secondary metabolism using the antiSMASH database. Nineteen BGCs were detected for each non-pigmented strain, while more than thirty BGCs were found for two of the pigmented strains. Among these, the groups of genes of nonribosomal peptide synthetases (NRPS) that code for bromoalterochromides stand out the most. Our results show that all strains possess BGCs for the production of secondary metabolites, and a considerable number of distinct polyketide synthases (PKS) and NRPS clusters are present in pigmented strains. Furthermore, the molecular networking analyses revealed two new molecules produced during microbial interactions: the dibromoalterochromides D/D' (11-12).

Characterizing changes in soil microbiome abundance and diversity due to different cover crop techniques

Soil-based microorganisms assume a direct and crucial role in the promotion of soil health, quality and fertility, all factors known to contribute heavily to the quality and yield of agricultural products. Cover cropping, used in both traditional and organic farming, is a particularly efficient and environmentally favorable tool for manipulating microbiome composition in agricultural soils and has had clear benefits for soil quality and crop output. Several long-term investigations have evaluated the influence of multi-mix (multiple species) cover crop treatments on soil health and microbial diversity. The present study investigated the short-term effects of a seven species multi-mix cover crop treatment on soil nutrient content and microbial diversity, compared to a single-mix cover crop treatment and control. Analysis of 16S sequencing data of isolated soil DNA revealed that the single-mix cover crop treatment decreased overall microbial abundance and diversity, whereas the control and multi-mix treatments altered the overall microbial composition in similar fluctuating trends. Furthermore, we observed significant changes in specific bacteria belonging to the phyla Acidobacteria, Actinobacteria, Planctomycetes, Proteobacteria and Verrucombicrobia for all treatments, but only the single-mix significantly decreased in abundance of the selected bacteria over time. Our findings indicate that the control and multi-mix treatments are better at maintaining overall microbial composition and diversity compared to the single-mix. Further study is required to elucidate the specific difference between the treatment effect of the multi-mix treatment and the control, given that their microbial composition changes over time were similar but they diverge into two populations of unique bacterial types by the end of this short-term study.

New Molecular Tools for Regulation and Improvement of A40926 Glycopeptide Antibiotic Production in Nonomuraea gerenzanensis ATCC 39727

Genome sequencing has revealed that Nonomuraea spp. represent a still largely unexplored source of specialized metabolites. Nonomuraea gerenzanensis ATCC 39727 is the most studied representative species since it produces the glycopeptide antibiotic (GPA) A40926 – the precursor of the clinically relevant antibiotic dalbavancin, approved by the FDA in 2014 for the treatment of acute skin infections caused by multi-drug resistant Gram-positive pathogens. The clinical relevance of dalbavancin has prompted increased attention on A40926 biosynthesis and its regulation. In this paper, we investigated how to enhance the genetic toolkit for members of the Nonomuraea genus, which have proved quite recalcitrant to genetic manipulation. By constructing promoter-probe vectors, we tested the activity of 11 promoters (heterologous and native) using the GusA reporter system in N. gerenzanensis and in Nonomuraea coxensis; this latter species is phylogenetically distant from N. gerenzanesis and also possesses the genetic potential to produce A40926 or a very similar GPA. Finally, the strongest constitutive promoter analyzed in this study, aac(3)IVp, was used to overexpress the cluster-situated regulatory genes controlling A40926 biosynthesis (dbv3 and dbv4 from N. gerenzanensis and nocRI from N. coxensis) in N. gerenzanensis, and the growth and productivity of the best performing strains were assessed at bioreactor scale using an industrial production medium. Overexpression of positive pathway-specific regulatory genes resulted in a significant increase in the level of A40926 production in N. gerenzanensis, providing a new knowledge-based approach to strain improvement for this valuable glycopeptide antibiotic.

Kistamicin biosynthesis reveals the biosynthetic requirements for production of highly crosslinked glycopeptide antibiotics

Kistamicin is a divergent member of the glycopeptide antibiotics, a structurally complex class of important, clinically relevant antibiotics often used as the last resort against resistant bacteria. The extensively crosslinked structure of these antibiotics that is essential for their activity makes their chemical synthesis highly challenging and limits their production to bacterial fermentation. Kistamicin contains three crosslinks, including an unusual 15-membered A-O-B ring, despite the presence of only two Cytochrome P450 Oxy enzymes thought to catalyse formation of such crosslinks within the biosynthetic gene cluster. In this study, we characterise the kistamicin cyclisation pathway, showing that the two Oxy enzymes are responsible for these crosslinks within kistamicin and that they function through interactions with the X-domain, unique to glycopeptide antibiotic biosynthesis. We also show that the kistamicin OxyC enzyme is a promiscuous biocatalyst, able to install multiple crosslinks into peptides containing phenolic amino acids.

Kistamicin is a structurally divergent glycopeptide antibiotic (GPA) that contains a unique 15-membered A-O-B ring. Here, the authors obtained a crystal structure of the kistamicin OxyA/X-domain complex and analysed the cyclisation cascade leading to the formation of the A-O-B ring.

Genomic-driven discovery of an amidinohydrolase involved in the biosynthesis of mediomycin A

Clethramycin (1) and mediomycin A (2) belong to the linear polyene polyketide (LPP) family of antibiotics that exhibit potent antifungal activity. Structural similarities exist between 1 and 2, except that 2 contains an amino moiety substituted for the guanidino moiety. Herein, the draft genome sequence of Streptomyces mediocidicus ATCC23936, a strain which produces both 1 and 2, was obtained through de novo sequencing. Bioinformatic analysis of the genome revealed a clethramycin (cle) gene cluster that contained 25 open reading frames (orfs). However, amidinohydrolase for 2 formation was not found in the cle gene cluster. Further genomic analysis revealed an amidinohydrolase MedX, which can hydrolyse the guanidino form (1) into the amino form (2) via heterologous co-expression of the cle cluster in Streptomyces lividans or by in vitro catalysis. These results also suggest the feasibility of engineering novel LPPs for drug discovery by manipulating the biosynthetic machinery of S. mediocidicus.