The dual production of NA4 and NA6, together with its alkaline nature, distinguishes MARAS458A from previously reported Microbulbifer β -agarases, suggesting structural variations affecting substrate processing and product specificity.
Background: Soil streptomycetes, particularly those isolated from extreme environments, are valuable sources of bioactive compounds. Their genomes encode a large number of biosynthetic gene clusters (BGCs), many of which can be simultaneously expressed. Methods: Molecular genetic methods were employed to identify Streptomyces anulatus 89 (Illumina NovaSeq 2 × 150 bp). Whole-genome phylogeny based on orthologous genes was employed using the Bacterial and Viral Bioinformatics Resource Centre services. Liquid chromatography–mass spectrometry analysis of biomass extract was carried out to identify antibiotics. Bioassays on cell lines were employed to evaluate the cytotoxicity and antitumor activity of the crude extract of the S. anulatus 89 strain. Results: Genome analysis identified 36 BGCs associated with secondary metabolites. The strain synthesized nactins, pladienolide, phenazinomycin, and 21-hydroxyoligomycin. The biomass extract demonstrated cytotoxicity against cancer cells and induced apoptosis. The A549 and A431 cell lines were the most sensitive. Changes in tumor cell morphology included rounding, shrinkage, increased granularity, and vacuolization. Conclusions: The ability of S. anulatus 89 to simultaneously synthesize different classes of anticancer antibiotics was reported. The investigated crude extract exhibited pronounced antitumor activity, making it a promising candidate for further studies. The underlying hypothesis suggested that strains with broad adaptive potential may serve as promising producers of natural products with antitumor properties.
Andrii Sylchuk, M. Loboda, Ivan Roman et al.· Applied Sciences· 0 citations
Idiomarina sp. D18 is a deep-sea marine bacterium isolated from seawater at a depth of 5069 m in the western Pacific Ocean. The complete genome of strain D18 consists of a circular chromosome of 2,765,208 bp and three plasmids, with a G + C content of 47.28%. Genome annotation identified 2587 predicted protein-coding genes, 57 tRNA genes, and 14 rRNA genes. Functional analysis revealed genes involved in diverse metabolic processes, including amino acid metabolism, signal transduction, and energy production. In addition, multiple carbohydrate-active enzymes were identified, suggesting the ability to utilize complex substrates in marine environments. Genome mining identified two biosynthetic gene clusters, including a RiPP-like cluster and a β-lactone cluster. These clusters are predicted to encode bioactive compounds, which may contribute to microbial competition and interaction through antimicrobial activity and enzyme inhibition. These findings suggest that strain D18 possesses adaptive strategies for survival in deep-sea environments and highlight its potential as a source of novel secondary metabolites.
Weifeng Liu, Conghui Huang, Aifang Deng et al.· Marine Genomics· 0 citations
While Paenibacillus polymyxa is widely recognized for its biocontrol capabilities, most characterized strains originate from soil or rhizosphere environments, leaving animal-associated populations largely unexplored. In this study, we report the isolation of P. polymyxa strain CACC1094 from the bovine rumen and its genome-guided characterization to investigate its biosynthetic potential and antifungal activity. Whole-genome sequencing yielded a complete circular chromosome of 5.55 Mb with a GC content of 45.36%, comprising 5,099 coding sequences, 39 rRNA genes, and 111 tRNA genes. Comparative phylogenomic analysis placed CACC1094 within the P. polymyxa species complex, clustering most closely with the rumen-associated strain ND24 (ANI: 98.31%) and strain 188 (ANI: 96.92%), while forming a distinct branch within the species. Genome mining identified 13 biosynthetic gene clusters, including those associated with fusaricidin and tridecaptin biosynthesis, a paenicidin-like lanthipeptide cluster, and a hybrid NRPS–PKS cluster. In dual-culture assays, CACC1094 showed broad in vitro antifungal activity against multiple plant-pathogenic fungi and oomycetes, as well as selected fungal and yeast pathogens of clinical and veterinary relevance. LC-QTOF/MS analysis of culture supernatants confirmed the production of fusaricidin A and fusaricidin B, providing direct experimental validation of genome-derived predictions. Additionally, genome annotation revealed a complete CRISPR-Cas adaptive immune system, suggesting an integrated ecological strategy that combines antimicrobial biosynthesis with defense against mobile genetic elements. Together, these findings identify CACC1094 as a rumen-associated P. polymyxa strain with broad-spectrum antifungal activity and experimentally validated fusaricidin production, highlighting its potential as a source of antifungal metabolites for agricultural and veterinary applications.
Bacillus velezensis strains BP5 and BP103, isolated from pepper rhizosphere soil in the Mekong Delta, Vietnam, displayed potent antagonistic activity against Xanthomonas euvesicatoria, which causes pepper bacterial spot. In dual-culture assays, BP5 formed the largest inhibition zone (36.7 mm), outperforming BP103 (32.1 mm) and oxolinic acid (31.3 mm). Both Gram-positive, rod-shaped strains produced extracellular protease, lipase, amylase, cellulase, and siderophores. Whole-genome sequencing revealed compact and genetically stable genomes: BP5 (4.08 Mb, 46.04% GC, 4,047 protein-coding genes, 5 prophages) and BP103 (3.91 Mb, 46.46% GC, 3,793 genes, 2 prophages). Phylogenetic reconstruction and average nucleotide identity (ANI of more than 98%) confirmed their assignment to B. velezensis, with closest relatedness to strain 160. Orthologous gene analysis across 28 B. velezensis genomes and B. subtilis DSM10 identified 2,593 single-copy genes. Compared to BP103, BP5 harbors greater numbers of multi-copy orthologs, other orthologs, and unique paralogs (388, 910, and 5 in BP5 with 336, 763, and 1 in BP103, respectively). Pangenome analysis showed that the core genome size decreased progressively with the addition of new genomes; BP5 showed more pronounced genetic divergence driven by expanded unique paralogs and shell gene families (with 456 in BP5 compared with 203 in BP103). Both strains encode 13 secondary metabolite biosynthetic gene clusters, including surfactin, fengycin, bacillaene, macrolactin, difficidin, bacilysin, bacillibactin, mersacidin, and locillomycin, plus four previously undescribed terpene/PKS. The CAZyme repertoire was richest in BP5 (133 genes), exceeding BP103 and the commercial strain FZB42 (both 129 genes), thereby enhancing adhesion and adhesion and rhizosphere colonization. These findings establish BP5 and BP103 as highly promising biocontrol agents, combining high genetic stability with diverse secondary metabolite profiles, suitable for development into sustainable microbial bio-bactericides.
Lê Uyển Thanh, Vu Nhat Tan, T. Huyen et al.· Frontiers in Microbiology· 0 citations
A polyphasic taxonomic approach was used to characterize strain B38T, isolated from the phyllosphere of Salicornia hispanica. The strain is an aerobic, Gram-negative, halotolerant coccus–rod-shaped bacterium exhibiting optimal growth at 28 °C, pH 6–9, and up to 12% (w/v) NaCl. The genome of strain B38T is 3.2 Mbp with a DNA G+C content of 43.81 mol%. Phylogenetic analysis based on the 16S rRNA gene sequences placed B38T within the genus Psychrobacter. Although 16S rRNA gene sequencing showed high similarity to P. alimentarius (99.73%), genomic indices (ANI, AAI, and dDDH) remained below species delimitation thresholds. Chemotaxonomic features included C18:1 ω9c as the major fatty acid, Q-8 as the main quinone, and diphosphatidylglycerol as the major polar lipid. Consequently, strain B38T (=CECT 31210; =LMG 33901) is proposed as Psychrobacter halotolerans sp. nov. Additionally, the plant growth-promoting (PGP) potential of the halotolerant strain B38T was evaluated in lettuce under salt stress, alongside the salt-tolerance mechanisms induced by inoculation. Strain B38ᵀ significantly enhanced lettuce biomass, leaf area, and PSII quantum efficiency compared to non-inoculated controls. These benefits were linked to increased soluble sugars and phenolic compounds, modulation polyamine homeostasis, and reduced oxidative damage. Our results demonstrate that P. halotolerans B38ᵀ effectively mitigates salt stress in plants, representing a promising biotechnological tool for enhancing salinity tolerance in agricultural systems.
Patricia Sánchez, F. Martínez-Checa, Francisco Palma et al.· Frontiers in Microbiology· 0 citations
Actinobacteria of the genus Streptomyces are widely recognised as a major reservoir of antibiotics. These bacteria occur abundantly in diverse environments, including soil, freshwater, and marine ecosystems. In this study, we employed isolation, characterisation, and analytical approaches encompassing morphological, genomic, and metabolomic techniques to investigate the potential of isolate HPM-9-01/B9-A, obtained from a pine forest in Mentaos, South Kalimantan, as a candidate for antibiotic production. Morphological characterisation combined with 16S rRNA sequencing identified the strain as Streptomyces albulus. Antibacterial assays demonstrated inhibitory activity against five pathogenic bacteria, with a strong inhibition zone of 16.75 ± 2.50 mm observed for Salmonella typhimurium. LC-MS analysis, supported by secondary metabolite identification using MassLynx and ChemSpider, revealed three major compounds: C10H16N7O2, C12H18NO3, and C17H21N4O5. These metabolites are predicted to possess antibacterial and neuroactive properties. Collectively, these findings highlight the promising potential of Streptomyces sp. isolate HPM-9-01/B9-A as a source of novel antibiotic compounds.
Dwi Ariyanti, Maya Fitriana, A. B. Kusuma et al.· International Conference on...· 0 citations