Search Results (1,295)

Background/Objectives: Actinobacteria are one of the largest bacterial phyla. These microbes produce bioactive compounds, such as antifungals, antibiotics, immunological modulators, and anti-tumor agents. Studies on actinobacteria isolated from the Brazilian Savannah biome (Cerrado) are scarce and mostly address metagenomics or the search for hydrolytic enzyme-producing microbes. Solanum lycocarpum (lobeira) is a tree widely employed in regional gastronomy and pharmacopeia in Central Brazil. Methods: In this work, 60 actinobacteria isolates were purified from the rhizosphere of S. lycocarpum. Eight Streptomyces spp. isolates were selected for in vitro antifungal activity against Cryptococcus neoformans H99, the C. neoformans 89-610 fluconazole-tolerant strain, C. gattii NIH198, Candida albicans, C. glabrata, and C. parapsilosis. The ability of the aqueous extracts of the isolates to induce the in vitro secretion of tumor necrosis factor (TNF-α), nitric oxide (NO), interleukin-6 (IL-6), and IL-10 by murine macrophages was also evaluated. Results: All extracts showed antifungal activity against at least two yeast species. Streptomyces spp. LAP11, LDB2, and LDB17 inhibited C. neoformans growth by 40–93%. Most extracts (except LAP2) also inhibited C. gattii. None inhibited C. albicans, but all inhibited C. glabrata (40–90%). Streptomyces sp. LAP8 extract increased nitric oxide production by approximately 347-fold in murine macrophages, while LDB11 extract suppressed LPS-induced TNF-α production by 70% and simultaneously increased IL-10 secretion, suggesting immunosuppressive potential. Conclusions: The results revealed that Cerrado actinobacteria-derived aqueous extracts are potential sources of antifungal and immunomodulatory biocompounds. Full article

The present research features an experimental comparative design and the objective of this work was to determine the susceptibility to microbiological contamination in fatty acid methyl esters (FAMEs) and the FAME–water interface of residual and refined lard, large volume simulating storage conditions as fuel supply chain, and to identify the microorganisms developed. The plates were seeded according to ASTM E-1259 and the instructions provided by the manufacturer of the Bushnell Haas agar. Microbiological growth was observed at the FAME–water interface of FAME obtained from residual lard. Using the MALDI-TOF mass spectrometry technique, Pseudomonas aeruginosa and Streptomyces violaceoruber bacteria were identified in the residual lard FAMEs, with the latter being previously reported in FAMEs. The implications of microorganism development on the physicochemical quality of FAMEs are significant, as it leads to an increase in the acid index, which may negatively impact metals by inducing corrosion. The refined lard FAMEs did not show any development of microorganisms. The present research concluded that residual lard tends to be more prone to microbiological attack if the conditions of water and temperature affect microbial growth. The findings will contribute to the knowledge base for a safer introduction of FAMEs into the biofuel matrix. Full article

Given the environmental significance of the textile industry, especially the accumulation of nondegradable materials, there is extensive development of greener approaches to fabric waste management. Here, we investigated the biodegradation potential of three Streptomyces strains in model compost on polyamide (PA) and polyamide-elastane (PA-EA) as synthetic, and on cotton (CO) as natural textile materials. Weight change of the materials was followed, while Fourier-Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were used to analyze surface changes of the materials upon biodegradation. The bioluminescence-based toxicity test employing Aliivibrio fischeri confirmed the ecological safety of the tested textiles. After 12 months, the increase of 10 and 16% weight loss, of PA-EA and PA, respectively, was observed in compost augmented with Streptomyces sp. BPS43. Additionally, a 14% increase in cotton degradation was recorded after 2 months in compost augmented with Streptomyces sp. NP10. Genome exploration of the strains was carried out for potential plastic-degrading enzymes. It highlighted BPS43 as the most versatile strain with specific amidases that show sequence identity to UMG-SP-1, UMG-SP-2, and UMG-SP-3 (polyurethane degrading enzymes identified from compost metagenome). Our results showcase the behavior of Streptomyces sp. BPS43 in the degradation of PA and PA-EA textiles in composting conditions, with enzymatic potential that could be further characterized and optimized for increased synthetic textile degradation. Full article

Streptomyces sp. AWH31-250, isolated from a tidal mudflat in the Nakdong River estuary in Busan, Republic of Korea, was found to produce two novel p-aminoacetophenone derivatives, mohangic acid H (1) and mohangiol (2). Their planar structures were established by comprehensive 1D and 2D NMR spectroscopy, mass spectrometry, and UV analysis, possessing a shorter carbon-chain with a diene moiety, whereas known mohangic acids A–F bear a longer carbon-chain with a triene moiety. The absolute configurations of the key stereogenic centers were determined via computational DP4+ calculations and bioinformatic analysis of the ketoreductase domain sequence from the biosynthetic gene cluster. Based on the careful gene analysis along with whole-genome sequencing, the first plausible biosynthetic pathway of mohangic acids A–G and mohangiol was proposed. Mohangic acid H (1) and mohangiol (2) displayed moderate inhibitory activity against Candida albicans isocitrate lyase with IC₅₀ values of 21.37 and 21.12 µg/mL, respectively. Full article

Straw-returning is an effective way to improve straw utilization efficiency and reduce environmental pollution. Various straw-returning methods exist; however, their effects on soil microbial diversity and community composition in cool regions have been little studied. This study investigated the changes of soil microbial diversity and community composition under three straw-returning methods, i.e., straw mulching, straw mulching and overturning, straw crushed and mixed, as compared to straw removal as control. The results showed that straw-returning could alter the soil microbial community composition and abundance compared with straw removal. Alpha diversity analysis showed that straw mulching treatment, and straw crushed and mixed treatment significantly increased the diversity of both soil bacteria and fungi compared with straw mulching and overturning treatment. Moreover, this study preliminarily screened Trichoderma, Chaetomium and Streptomyces as potential straw-degrading microorganisms. This study provides basis for further enhancement of straw degradation by using soil microorganisms and sheds light on future work for improving straw degradation efficiency. Full article

Antimicrobial resistance (AMR) has emerged as a global health crisis, with methicillin-resistant Staphylococcus aureus (MRSA) representing one of the most clinically significant multidrug-resistant pathogens. In this study, three structurally unique anthracycline derivatives—keto-ester (1), 4-deoxy-ε-pyrromycinone (2), and misamycin (3)—were first isolated and characterized from the fermentation broth of the marine-derived Streptomyces tauricus NBUD24. These compounds exhibited notable antibacterial efficacy against MRSA, with minimum inhibitory concentrations (MICs) ranging from 16 to 32 µg/mL. Cytotoxicity assays confirmed their safety profile at therapeutic concentrations. The biofilm formation assay demonstrated that 4-deoxy-ε-pyrromycinone inhibited biofilm formation of MRSA ATCC43300, with an inhibition rate of 64.4%. Investigations of antibacterial mechanisms revealed that these compounds exert antibacterial effects primarily through disruption of bacterial cell wall integrity and destruction of DNA structure. These findings underscore the potential of marine-derived microbial metabolites as promising scaffolds for developing next-generation antimicrobial candidates to combat drug-resistant infections. Full article

In this paper, cultivable actinobacteria were isolated, cultured, and identified from the heavily algal-bloomed waters of Taihu Lake using 16S rRNA gene sequencing. Among the isolates, a single strain exhibiting vigorous cyanocidal activity against Microcystis aeruginosa FACHB-905 was selected for further investigation. The cyanocidal efficacy and underlying mechanisms of this strain, designated TH05, were assessed through using chlorophyll content, cyanobacterial inhibition rate, and cyanobacterial cell morphology measurements. In addition, oxidative stress responses, expression of key functional genes in FACHB-905, and variations in microcystin concentrations were comprehensively evaluated. Cyanobacterial blooms caused by Microcystis aeruginosa pose serious ecological and public health threats due to the release of microcystins (MCs). In this study, we evaluated the cyanocidal activity and mechanism of a novel actinomycete strain, Streptomyces sp. TH05. Optimization experiments revealed that a light–dark cycle of 12 h/12 h, temperature of 25 °C, and pH 7 significantly enhanced cyanocidal efficacy. Under these conditions, TH05 achieved an 84.31% inhibition rate after seven days of co-cultivation with M. aeruginosa. Scanning electron microscopy revealed two distinct cyanocidal modes: direct physical attachment of TH05 mycelia to cyanobacterial cells, causing cell wall disruption, and indirect membrane damage via extracellular bioactive compounds. Biochemical analyses showed increased levels of malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) during the first five days, peaking at 2.47-, 2.12-, and 1.91-fold higher than control levels, respectively, indicating elevated oxidative stress. Gene expression analysis using elf-p as a reference showed that TH05 modulated key genes associated with photosynthesis (PsaB, PstD1, PstD2, RbcL), DNA repair and stress response (RecA, FtsH), and microcystin biosynthesis (McyA, McyD). All genes were upregulated except for RbcL, which was downregulated. In parallel, microcystin content peaked at 32.25 ng/L on day 1 and decreased to 16.16 ng/L by day 9, which was significantly lower than that of the control group on day 9 (29.03 ng/L). These findings suggest that strain TH05 exhibits potent and multifaceted cyanocidal activity, underscoring its potential for application in the biological control of cyanobacterial blooms. Full article

Clubroot, caused by Plasmodiophora brassicae Woronin, poses a major threat to Chinese cabbage (Brassica rapa subsp. pekinensis) production worldwide, significantly impacting crop yield, quality, and economic value. Biological control represents a promising approach since it is non-toxic and eco-friendly, and it reduces the risk of pathogen resistance development. In this study, our objective was to screen for actinomycetes that can effectively inhibit clubroot. We screened 13 actinomycete strains, identifying 2, XDS3-6 and CD1-1, with substantial in vivo inhibitory effects, achieving infection suppression rates above 64% against P. brassicae. Phylogenetic analysis classified XDS3-6 and CD1-1 as Streptomyces virginiae and Streptomyces cinnamonensis, respectively. Both strains exhibited protease and glucanase production capabilities, essential for pathogenic suppression. Additionally, these strains induced host defense responses, as evidenced by increased jasmonic acid (JA) and salicylic acid (SA) accumulation and elevated activities of defense-related enzymes. Colonization studies of XDS3-6 and CD1-1 mutant strains in cabbage roots indicated sustained root colonization, with peak colony-forming units (CFUs) at 20 days post-inoculation, reaching 11.0 × 10⁴ CFU/g and 8.5 × 10⁴ CFU/g, respectively, and persisting for at least 30 days. Overall, these findings underscore the potential of Streptomyces strains XDS3-6 and CD1-1 as effective biocontrol agents, providing a theoretical foundation for their application in managing clubroot in Chinese cabbage. Full article

This study investigates the potential for the microbial transformation of camelliagenin B, a saponin derived from Camellia oleifera seed cake meal, to develop novel metabolites. We employed three microbial strains, specifically Bacillus subtilis ATCC 6633, Bacillus megaterium CGMCC 1.1741, and Streptomyces griseus ATCC 13273, to biotransform camelliagenin B into its derivatives. The compounds were purified and separated using chromatographic techniques, such as high-performance liquid chromatography (HPLC). Structural identification was carried out using spectroscopic methods, including nuclear magnetic resonance (NMR) and mass spectrometry (MS). Ten bioactive compounds were obtained (1a-1j), of which nine were novel with multiple tailoring reactions, such as allyl oxidation, C-C double-bond rearrangement, hydroxylation, dehydrogenation, and glycosylation, observed in camelliagenin B analogs. The structures of these compounds were determined by 1D/2D NMR and HR-ESI-MS analysis. Therefore, this study showcases the capacity of microbial transformation as a sustainable and environmentally friendly method for generating bioactive compounds from C. oleifera seed cake meals. The individual chemicals can potentially facilitate the design of novel medicinal agents, functional foods, and natural preservatives. Full article

The ongoing threat of antimicrobial-resistant pathogens has intensified the need for new antimicrobial agents, making the discovery of novel natural products crucial. This study focuses on the isolation and characterization of a novel Streptomyces species from the Anjar region in Lebanon, an area rich in microbial diversity that is largely unexplored for its biotechnological potential. Soil samples were collected and processed, leading to the isolation of Streptomyces strain ANJ10. Comprehensive morphological, physiological, and genomic analyses were conducted, including whole-genome sequencing (WGS) to identify biosynthetic gene clusters (BGCs) and broth microdilution (BMD) assays to evaluate antimicrobial activity. The ANJ10 genome revealed 42 BGCs, significantly more than the average number in Streptomyces species, suggesting a high potential for secondary metabolite production. Phylogenetic analysis confirmed ANJ10 as a novel species, and BMD assays demonstrated its strong antimicrobial activity against several gram-negative pathogens, specifically, Acinetobacter baumannii. These findings underscore the potential of this strain as a significant source of new antimicrobial compounds, reinforcing the importance of exploring underexploited environments like Lebanon for microbial bioprospecting. Full article

The long-term monocropping of red kidney beans in agricultural fields can lead to the occurrence of soil-borne diseases. Alterations in the composition of the soil microbial community are a primary cause of soil-borne diseases and a key factor in continuous cropping obstacles. Research exploring how different cultivation modes can modify the diversity and composition of the rhizosphere microbial community in red kidney beans, and thus mitigate the effects of continuous cropping obstacles, is ongoing. This study employed three cultivation modes: the continuous monocropping of red kidney beans, continuous monocropping of soybeans, and red kidney bean–soybean intercropping. To elucidate the composition and diversity of rhizosphere microbial communities, we conducted amplicon sequencing targeting the V3-V4 hypervariable regions of the bacterial 16S rRNA gene and the ITS1 region of fungal ribosomal DNA across distinct growth stages. The obtained sequencing data provide a robust basis for estimating soil microbial diversity. We observed that, under the intercropping mode, the composition of both bacteria and fungi more closely resembled that of soybean monocropping. The monocropping of red kidney beans increased the richness of rhizosphere bacteria and fungi and promoted the accumulation of pathogenic microorganisms. In contrast, intercropping cultivation and soybean monocropping favored the accumulation of beneficial bacteria such as Bacillus and Streptomyce, reduced pathogenic fungi including Alternaria and Mortierell, and exhibited less microbial variation across different growth stages. Compared to the monocropping of red kidney beans, these systems demonstrated more stable microbial structure and composition. The findings of this study will inform sustainable agricultural practices and soil management strategies. Full article

Orobanche cumana Wallr. is a root parasitic plant that causes considerable yield losses of up to 50% in sunflower Helianthus annuus plantations. The holoparasite fulfills its entire demand for water, minerals, and organic nutrients from the host’s vascular system. Agronomic practices alone are not effective in controlling this pest. This study investigated the mechanism of a verified plant growth-promoting strain, Streptomyces rochei D74, on the inhibition of the parasitism of O. cumana in a co-culture experiment. We conducted potted and sterile co-culture experiments using sunflower, O. cumana, and S. rochei D74. Our results suggest that the inoculated bacteria invoked the sunflower systemic resistance (SAR and ISR) by increasing the activity of resistance-related enzymes (SOD, POD, PPO, and PAL), the gene expression of systemic resistance marker genes (PR-1 and NPR1), ethylene synthesis genes (HACS. 1 and ACCO1), and JA synthesis genes (pin2 and lox). The expression levels of ISR marker genes (lox, HACS. 1, ACCO1, and pin2) increased by 1.66–7.91-fold in the seedling stage. Simultaneously, S. rochei D74 formed a protective layer on the sunflower root surface, preventing O. cumana from connecting to the vascular system of the sunflower roots. In addition, S. rochei D74 reduced 5DS synthesis of the strigol precursor substance, resulting in a reduction in O. cumana germination. These results demonstrated that the S. rochei D74 strain improved systemic resistance and decreased seed germination to prevent O. cumana parasitism. Full article

With the increasing severity of global climate change and soil salinization, the development of microorganisms that enhance crop salt tolerance has become a critical focus of agricultural research. In this study, we explored the potential of a novel Streptomyces species Qhu-G9 as a plant growth-promoting rhizobacterium (PGPR) under salt stress conditions, employing whole-genome sequencing and functional annotation. The genomic analysis revealed that Qhu-G9 harbors various genes related to plant growth promotion, including those involved in phosphate solubilization, indole-3-acetic acid (IAA) biosynthesis, antioxidant activity, and nitrogen fixation. A total of 8528 coding genes were annotated in Qhu-G9, with a significant proportion related to cell metabolism, catalytic activity, and membrane transport, suggesting its broad growth-promoting potential. In vitro experiments demonstrated that Qhu-G9 exhibited strong iron siderophore production, IAA synthesis, phosphate solubilization, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, all of which correlate with its plant growth-promoting capacity. Further plant growth trials revealed that Qhu-G9 significantly enhances the growth of Avena sativa and Onobrychis viciifolia seedlings under salt stress conditions, improving key physiological parameters, such as chlorophyll content, relative water content, and photosynthetic efficiency. Under salt stress conditions, inoculation with Qhu-G9 resulted in notable increases in total biomass, root length, and plant height. Biochemical analyses further confirmed that Qhu-G9 alleviates the oxidative damage induced by salt stress by boosting antioxidant enzyme activities, reducing peroxide levels, and promoting the accumulation of osmotic regulators. These findings suggest that Qhu-G9 holds great promise as a PGPR that not only promotes plant growth, but also enhances plant tolerance to salt stress; thus, it has significant agricultural potential. Full article

Verticillium wilt, caused by Verticillium dahliae, poses a significant threat to olive trees (Olea europaea L.). The isolation of endophytic Streptomyces strains from olive roots has led to the discovery of several strains showing strong antifungal activity against V. dahliae, as demonstrated through in vitro and small-scale soil experiments. Molecular analyses confirmed that strain OE54 belongs to Streptomyces iranensis. The main antifungal compound identified in this strain was rapamycin. Rapamycin displayed potent antifungal effects, notably inhibiting conidiospore germination (IC₅₀ = 87.36 μg/mL) and the hyphal growth of V. dahliae, with a minimum inhibitory concentration (MIC₅₀) of 3.91 ng/mL. Additionally, a second rapamycin-producing strain, OE57^T, was isolated. Phenotypic and genotypic analyses indicated that OE57^T represents a new species, which is proposed to be named Streptomyces lacaronensis sp. nov., with OE57^T designated as the type strain (=DSM 118741^T; CECT 31164^T). The discovery of two endophytic rapamycin-producing Streptomyces strains residing within olive roots is especially notable, given the rarity of rapamycin production among microorganisms. These findings highlight the potential of rapamycin-producing Streptomyces strains in developing biofertilizers to manage V. dahliae and reduce the impact of Verticillium wilt on olive trees and other crops. Full article

Guvermectin, a Streptomyces-derived purine nucleoside compound, exhibits dual bioactivities as a plant growth regulator and an antibacterial agent. While its biosynthetic gene cluster (BGC) is regulated by the cluster-situated activator GvmR and the adjacent repressor GvmR2, the role of distal transcriptional regulators (TRs) in guvermectin biosynthesis remains unexplored. Here, we identified ScnR1, a highly conserved LacI-family TR located far from the guvermectin BGC, which is directly activated by GvmR. Overexpression of scnR1 significantly suppressed guvermectin biosynthesis. Further investigations revealed that ScnR1 competitively binds to the gvmR, gvmA, and O1 promoters (overlapping with the GvmR-binding sites), thereby inhibiting the guvermectin BGC transcription. Moreover, ScnR1 formed a reciprocal feedback loop with the adjacent repressor GvmR2, where each repressor inhibits the other’s expression. These findings reveal a multi-layered regulatory mechanism wherein LacI-family TRs fine-tune guvermectin biosynthesis through competitive DNA binding and reciprocal feedback control. This study offers new perspectives on the hierarchical control of secondary metabolism in Streptomyces and provides valuable theoretical guidance for the engineering of strains with enhanced natural product production. Full article