Search Results (124)

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

Chagas disease (ChD) caused by Trypanosoma cruzi remains a major public health concern, affecting approximately 8 million people worldwide. However, the number of undiagnosed cases is likely much higher. Existing treatments rely on benznidazole and nifurtimox which, despite their efficacy during the acute phase of infection, are often associated with severe side effects that can be life-threatening. As a promising alternative, actinomycetes—which are renowned for producing pharmacologically and industrially relevant metabolites—have demonstrated potent antimicrobial properties; however, their antiparasitic potential remains largely unexplored. This study evaluated the anti-trypanocidal activities of extracellular metabolites produced by Streptomyces thermocarboxydus strain Chi-43 (ST-C43) and Streptomyces sp. strain Chi-104 (S-C104) against epimastigote, trypomastigote, and amastigote forms of T. cruzi. The strains were cultured in ISP2 broth, and their extracellular metabolites were assessed via antiparasitic diffusion assays in microplates. The 50% lethal concentration (LC₅₀) values ranged from 102 to 116 μg/mL against epimastigotes and trypomastigotes. The antiparasitic activity was confirmed through 3-(4,5-dimetiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based spectrophotometric assays and optical microscopy. Toxicity assays revealed that the extracellular metabolites were non-toxic to Artemia salina, non-cytotoxic to Huvecs, and non-hemolytic to human erythrocytes. Dose–response regression analysis showed statistically significant differences (p ≤ 0.05). LC-MS/MS analysis identified amphomycin and K-252c aglycone staurosporine as the active antiparasitic compounds. These findings highlight the potential of Streptomyces-derived extracellular metabolites as novel, selective, and safe anti-T. cruzi agents. Nevertheless, further studies in murine or preclinical models are needed to validate their efficacy and support future clinical applications for the treatment of ChD. Full article

Geosmin (GSM) and 2-methylisoborneol (2-MIB), microbial-derived terpenoid compounds prevalent in aquaculture systems, impair fillet quality and disrupt physiological homeostasis in aquatic species by inducing oxidative stress and lipid peroxidation. Despite their significant impact, effective strategies for eliminating these compounds from fish tissues remain underexplored. In this study, we employed primer-mediated PCR amplification to identify strains that produce 2-MIB and GSM and evaluated the efficacy of Bacillus licheniformis strain BL23 (BL23) in suppressing S. thermocarboxydus (ST), a key contributor to terpenoid synthesis. Experimental fish were allocated to three groups (n = 30 per group): Group C (control, standard feed), Group T1 (BL23-supplemented feed), and Group T2 (BL23 + ST coculture). Probiotic concentrations in the tanks were maintained at 10⁶ CFU/mL under controlled conditions (30 °C). Tissue and aqueous samples were collected at intervals for the analysis of texture, growth performance, and terpenoid concentrations, with measurements in triplicate. Subsequently, B. licheniformis strain BL23 (BL23), which exhibits inhibitory effects against S. thermocarboxydus (ST) growth, was cultured and introduced into both fish specimens and aqueous systems. The outcomes of strain inoculation and cultivation experiments demonstrated the emergence of an inhibition zone surrounding the actinomycetes inoculated with BL23. The results from liquid coculture assays revealed a reduction in the concentration of ST from 10⁶ CFU/mL at 48 h to 10¹ CFU/mL at 72 h post-coculture with BL23 for an initial 48 h period. An analysis of fish tissue and aqueous samples confirmed that BL23 exhibited a significant inhibitory effect on the growth of ST, leading to a substantial decrease in GSM content (p < 0.05). However, no statistically significant improvements were observed in fish growth performance (weight gain, feed conversion rate) or meat texture quality parameters (hardness, elasticity). These findings present a novel approach to mitigating geosmin-induced off-flavors in aquaculture products, highlighting its potential utility in water management and aquatic food production systems. The results are particularly pertinent for the development of biological control strategies targeting microbial-derived odorants in recirculating aquaculture systems. Full article

The high-input production mode of rice monoculture (RM) has caused severe soil degradation and biodiversity loss, necessitating a transition toward more sustainable practices. The traditional rice-fish co-culture (RF) may provide valuable insights for this situation. However, it remains elusive how long-term RF system influences soil microbial community structure, enzyme activities, and carbon (C) sequestration. Here, a study was conducted at two representative RF areas in Lianshan Zhuang and Yao Autonomous County. At Shatian (P1), three treatments included rice monoculture (RM1) and 2-year and 5-year RF (RF2, RF5). At Gaoliao (P2), the experimental treatments included rice monoculture (RM2) and 15 and 30 years of RF (RF15, RF30). We collected the surface layer (0–20 cm) soils. Then, we analyzed the chemical properties, phospholipid fatty acids (PLFA), and enzyme activities to investigate the effects of their variation on soil C sequestration. The results showed that RF treatments significantly increased soil organic C (SOC) content. Specifically, RF2 and RF5 treatments promoted the SOC content by 4.82% and 13.60% compared with RM1 treatment at P1, respectively; RF15 and RF30 treatments increased the SOC content by 23.41% and 31.93% compared with RM2 treatment at P2, respectively. Additionally, RF5 treatment significantly increased the biomass of the soil microbial community in comparison with RM1 treatment, as did RF15 treatment and RF30 treatment compared with RM2 treatment, including the contents of total PLFA and the PLFA of gram-positive bacteria (G+), gram-negative bacteria (G−), actinomycetes, fungi, and bacteria. Activities of β-glucosidase, cellobiohydrolase, β-1,4-N-acetylglucosaminidase, and urease significantly increased in RF5 and RF30 treatments. The piecewise SEM results indicated that the changes of total PLFA content and the PLFA content ratio of fungi to bacteria were related to contents of dissolved organic C (DOC) and total N (TN) under different RF durations, which are key indicators affecting SOC content. Overall, SOC storage increases with the RF durations, and soil microbial community structure may drive soil C sequestration under long-term RF, which provides a scientific significance and practical value in promoting the sustainability of agricultural ecosystems, enhancing the potential of soil as a carbon sink, and addressing global climate change. Full article

This study reveals how microbial diversity relates to soil properties in Auricularia heimuer residue–chicken manure composting, presenting sustainable waste recycling solutions. These microbial-straw strategies are adaptable to various agroecological regions, offering flexible residue valorization approaches for local conditions, crops, and resources. This study examined the effects of composting Auricularia heimuer residue and chicken manure at three ratios (6:4, 7:3, 8:2) on soil properties, lignocellulose content, enzyme activity, microbial diversity, and maize growth. The compost was mixed into potting soil at different proportions (0:10 to 10:0). During composting, the temperature remained above 50 °C for more than 14 days, meeting safety and sanitation requirements. The composting process resulted in a pH range of 7–8, a stable moisture content of 60%, a color change from brown to gray-brown, the elimination of unpleasant odors, and the formation of loose aggregates. Lignocellulose content steadily decreased, while lignocellulosic enzyme activity and actinomycete abundance increased, indicating suitability for field application. Compared with the control (CK), total nitrogen, total phosphorus, and total potassium in the soil increased by 57.81–77.91%, 4.5–19.28%, and 301.09–577.2%, respectively. Lignin, cellulose, and hemicellulose increased 50.6–83.49%, 59.6–340.33%, and 150.86–310.5%, respectively. The activities of lignin peroxidase, cellulase, and hemicellulase increased by 9.05–36.31%, 6.7–36.66%, and 37.39–52.16%, respectively. Maize root weight, plant biomass, and root number increased by 120.87–138.59%, 117.83–152.86%, and 29.03–75.81%, respectively. In addition, composting increased the relative abundance of actinomycetes while decreasing the abundance of ascomycetes and ascomycetes. The relative abundance of Sphingomonas and Gemmatimonas increased, whereas pathogenic fungi such as Cladosporium and Fusarium decreased. Compost application also enhanced bacterial and fungal diversity, with bacterial diversity indices ranging from 6.744 to 9.491 (B1), 5.122 to 9.420 (B2), 8.221 to 9.552 (B3), and 6.970 to 9.273 (CK). Fungal diversity indices ranged from 4.811 to 8.583 (B1), 1.964 to 9.160 (B2), 5.170 to 9.022 (B3), and 5.893 to 7.583 (CK). Correlation analysis of soil physicochemical properties, lignocellulose content, enzymes, microbial community composition, and diversity revealed that total nitrogen, total phosphorus, total potassium, and lignocellulose content were the primary drivers of rhizosphere microbial community dynamics. These factors exhibited significant correlations with the dominant bacterial and fungal taxa. Additionally, bacterial and fungal diversity increased with the incorporation of Auricularia heimuer residue. In conclusion, this study elucidates the relationships between microbial diversity and soil properties across different proportions of Auricularia heimuer residue and chicken manure composting, offering alternative strategies for waste recycling and sustainable agricultural development. At present, the production of biobiotics using waste culture microorganisms is still in the laboratory research stage, and no expanded experiments have been carried out. Therefore, how to apply waste bacterial bran to the production of biocontrol biotics on a large scale needs further research. Full article

This study investigated the effect of different culture agar media, derived from Bennett’s medium, on the antimicrobial activity of 15 Streptomyces sp. and 1 Lentzea sp. strains isolated from mining environments. The media were prepared from the standard Bennett’s medium by suppressing one, two, or three ingredients—yeast extract (YE), beef extract (BE), or casein (Cas)—while maintaining glucose (Gluc) or by substituting it with fructose (Fruc) or galactose (Gal) and keeping the same suppressions. The antimicrobial activity was investigated against Candida albicans ATCC 10231, Staphylococcus aureus ATCC 29213, Bacillus subtilis ATCC 6633, and Escherichia coli K12. The antimicrobial activity of actinomycete strains was positively influenced by media modifications, though the response was actinomycete strain and target pathogen-dependent. Unexpectedly, thirteen strains exhibited poor growth on a pure agar-agar medium, including six Streptomyces strains (AS34, AS3, BS59, BS68, BS69, and DAS104) that showed notable antimicrobial activity, with inhibition zone diameters ranging from 10.75 ± 1.06 to 18.00 ± 0.00 mm. Modifications of Bennett’s medium, including replacing glucose with fructose or galactose and maintaining yeast extract or both yeast extract and beef extract, induced and enhanced the antimicrobial activity of several actinomycete strains. Notably, the new media induced antimicrobial activity in strains that showed no activity in Bennett’s medium. They led, compared to Bennett’s medium, to the detection of eight additional active strains against S. aureus, eight against B. subtilis, six against E. coli, and four against C. albicans. This study is the first to explore the modification of Bennett’s medium, either by subtraction or substitution, in order to investigate the effect on antimicrobial activity of actinomycete strains. These results highlight the importance of the composition of culture media on inducing or boosting antimicrobial activity in Streptomyces and Lentzea. Full article

Pseudopeptides are attractive agents for protease inhibition due to their structural similarities to the natural substrates of these enzymes, as well as their enhanced stability and resistance to enzymatic degradation. We report three new ketomemicin pseudopeptides (1–3) from extracts of the marine actinomycete Salinispora pacifica strain CNY-498. Their constitution and relative configuration were elucidated using NMR, mass spectrometry, and quantum chemical calculations. Using GNPS molecular networking and publicly available Salinispora LCMS datasets, five additional ketomemicin analogs (4–8) were identified with ketomemicin production detected broadly across Salinispora species. The ketomemicin biosynthetic gene cluster (ktm) is highly conserved in Salinispora, occurring in 79 of 118 public genome sequences, including eight of the nine named species. Outside Salinispora, ktm homologs were detected in various genera of the phylum Actinomycetota that might encode novel ketomemicin analogs. Ketomemicins 1–3 were tested against a panel of eleven proteases, with 2 displaying moderate inhibitory activity. This study describes the first report of ketomemicin production by Salinispora cultures, the distribution of the corresponding biosynthetic gene cluster, and the protease inhibitory activity of new ketomemicin derivatives. Full article

A high proteolytic-resistant hexapeptide (α_s1-CN 181–186) (1) along with two known 2,5-diketopiperazines, namely cyclo-(L-Pro-L-Phe) (2) and cyclo-(L-Pro-L-Tyr) (3), as well as the carboxylic acid 2-hydroxyphenylacetic acid (4), were isolated from the actinomycete strain CA287887. The morphological 16S rRNA gene sequence and phylogenetic data of the strain exhibited high similarity with members of the genus Actinomycetospora. The structure of 1 was thoroughly investigated for the first time through the extensive use of 1D and 2D NMR experiments while its absolute configuration was determined by Marfey’s analysis. The anti-tyrosinase effects of the aforementioned compounds were investigated in vitro using kojic acid as the positive control (IC₅₀ 14.07 μΜ). Compound 3 exhibited the highest activity (IC₅₀ 28.69 μΜ), followed by compound 4 (IC₅₀ 98.29 μΜ). Compound 1 was further evaluated for cytotoxicity against HepG2, A2058, A549, and MiaPaca-2 cell lines. At all the tested concentrations (0.01–200 μg/mL), no cytotoxic effect was observed. Full article

Four new kaurane-type diterpenoids, geliboluols A–D (1–4), along with one known analog (5), were isolated from the culture broth of the marine-derived rare actinomycete Actinomadura geliboluensis. The structures of compounds 1–4 were determined by spectroscopic analysis (HR-ESIMS, 1D, and 2D NMR), the MPA method, and by comparing their optical rotation values with those in the literature. The new compounds were evaluated for their cytotoxicity against seven blood cancer cell lines by a CellTiter-Glo (CTG) assay and six solid cancer cell lines by a sulforhodamine B (SRB) assay. Among the new compounds, compound 4 exhibited moderate cytotoxic activity against some blood cancer cell lines, with GI₅₀ values ranging from 2.59 to 19.64 µM, and against solid cancer cell lines with GI₅₀ values ranging from 4.34 to 7.23 µM. Full article

Biological control is considered one of the most important methods for preventing and controlling the worldwide fungal disease gray mold, caused by Botrytis cinerea. Among the various agents used in biological control, actinomycetes represent a significant group of microorganisms that offer valuable resources for biocontrol strategies. In this study, a total of 132 actinomycetes, belonging to four genera (Streptomyces, Kitasatospora, Amycolatopsis, and Nocardia), were isolated from soil. Among the five media tested, ISP-2 and GS NO.1 media were found to be highly suitable for isolating actinomycetes. It is worth mentioning that the strain TCS21-117 displayed significant inhibitory effects against Botrytis cinerea and nine other pathogenic fungi. The strain TCS21-117 was identified as Streptomyces roietensis by its morphological characteristics and phylogenetic analysis of the 16S rRNA gene. The optimum culture conditions for the strain TCS21-117 were a potato dextrose broth medium at an initial pH of 8.0, a liquid volume of 125 mL in a 250 mL flask, 180 r·min⁻¹ at 28 °C, and an inoculum size of 1% for 7 days. Under these conditions, the inhibition rate against Botrytis cinerea was 93.31%, a significant increase (31.98%) as compared to the control. Notably, the antifungal compounds produced by the strain TCS21-117 exhibited strong stability across a range of temperatures, pH levels, and durations of storage and UV irradiation. This study showed that the Streptomyces roietensis strain TCS21-117 had strong inhibitory activity against Botrytis cinerea under optimized fermentation conditions, enriching the microbial resources for gray mold control. Full article

Plant biostimulants have been the subject of intense interest in recent years. The aim of this study was to assess, during the years 2021–2022, the effect of mineral nitrogen (N) fertilizer, experimental (PGPB) and commercial (G) microbial biostimulants, and humic substance product (A) on the soil microbial communities, and yield of strawberries, under field conditions. Dehydrogenase activity was significantly affected by nitrogen fertilization, but an increase occurred in the treatment N+G. The treatments N+G, N+G+A, and N+PGPB+A increased FDA hydrolysis, and phosphatase activity. All plant biostimulants increased basal as well as substrate-induced respiration. Culturable bacteria (total counts, dormant forms, actinomycetes) were not clearly affected by treatment. Based on 16S rRNA analysis, bacterial community composition was different in N+PGPB+A and N+G+A treatments. The number of cultivable fungi was significantly lower in N+PGPB and N+PGPB+A treatments. The genus of fungi Pilidium, a potential phytopathogen of strawberries, was present in the second year, but in these treatments, it was absent. In the second year, strawberry yield was shown to be 95% higher in the N+PGPB+A treatment than in the control. Microbial biostimulants in combination with humic substances represent a potential solution in increasing strawberry production. Full article

Sustainable horticulture is crucially based on the greenhouse production of vegetables under controlled conditions. In this study, we wanted to learn how cultivated plants may impact indoor air quality and whether the workers can be exposed to bioaerosols in a similar way in these settings. The study objective was to test the hypothesis that the microbial concentrations, distribution of bioaerosol particle sizes, and composition of the airborne microbiome are specific to greenhouses, polytunnels, and open-air sites. The air samples were collected to assess the concentration of total culturable bacteria (TCB), fungi, actinomycetes, and β-haemolytic bacteria and for the identification of bacterial and fungal strains. Higher concentrations of TCB and fungi were found in the greenhouse (log 3.71 and 3.49 cfu m⁻³, respectively) than in polytunnels (log 2.60–2.48 and 2.51–2.31 cfu m⁻³, respectively) during the vegetation of cucumbers. These airborne microbes were represented by a significant contribution of the respirable fraction with a distinct contribution of fine particles in size below 4.7 µm. Cultivation of cucumbers resulted in the higher emission of airborne microorganisms in contrast with growing herbs such as oregano and basil. In total, 35 different bacteria and 12 fungal species, including pathogenic or allergenic agents, were identified within the studied sites. The workers can be exposed to increased concentrations of TCB and fungi in the greenhouse during the plant vegetation. It might be recommended to properly manage greenhouses and polytunnels, dispose of dust sources, and maintain appropriate ventilation to sustain relevant air quality. Full article

The atmospheric environment is formed under the influence of local and distant sources as a result of horizontal and vertical transport. In the present work, microbiological analysis of 604 samples of atmospheric aerosol collected in the period from September 2020 to September 2023 at four sites differing in anthropogenic load, located in Novosibirsk and the region, was carried out. Day and night aerosol samples were collected during 12 h every two weeks by filtration using Sartorius reinforced Teflon membranes, then sown on a set of nutrient media. The taxonomic affiliation of the isolated microbial isolates was determined based on phenotypic characteristics and analysis of 16S rRNA gene nucleotide sequences. Changes in the composition and concentration of culturable microorganisms depending on the season, time of day, and site of aerosol sampling were observed. In winter, lower fungi and bacteria of the genera Bacillus, Staphylococcus, Micrococcus dominated with an average concentration from zero to 12.5 CFU/m³ of aerosol. In the warm period, the concentration and diversity of cocci, spore-forming and non-spore-forming bacteria, actinomycetes, and fungi (up to 1970 CFU/m³), among which pathogenic microorganisms were found, increased sharply in aerosols. The use of 16S metabarcoding techniques has greatly expanded the range of aerosols’ microbial diversity detectable. Full article

This study explores the efficient decolorization and complete mineralization of the diazo dye Evans blue, using an integrated aerobic bioreactor system coupled with a double-chamber microbial fuel cell (DCMFC) including a bio-cathode and acetate as a cosubstrate. The research addresses the environmental challenges posed by dye-laden industrial effluents, focusing on achieving high decolorization efficiency and understanding the microbial communities involved. The study utilized mixed strains of actinomycetes, isolated from garden compost, to treat initial dye concentrations of 100 mg/L and 200 mg/L. Decolorization efficiency and microbial community composition were evaluated using 16S rRNA sequencing, and electrochemical impedance spectroscopy (EIS) was used to assess anode and DCMFC resistance. The results demonstrated decolorization efficiencies ranging from 90 ± 2% to 98 ± 1.9% for 100 mg/L and from 79 ± 2% to 87% ± 1% for 200 mg/L. An anode resistance of 12.48 Ω indicated a well-developed biofilm and enhanced electron transfer. The microbial community analysis revealed a significant presence of Pseudomonadota (45.5% in dye-acclimated cultures and 32% in inoculum cultures), with key genera including Actinomarinicola (13.75%), Thermochromatium (4.82%), and Geobacter (4.52%). This study highlights the potential of the integrated DCMFC–aerobic system, utilizing mixed actinomycetes strains, for the effective treatment of industrial dye effluents, offering both environmental and bioenergy benefits. Full article

Chemical fertilization is usually associated with some unreasonable problems that affect the sustainable production of tea gardens. The micro-organism fertilizer created from plant growth-promoting microbes (PGPM) integrates the beneficial properties of functional micro-organisms and bioinoculants. Application of PGPM can activate soil nutrients, prevent soil-borne diseases, and promote crop growth, thus improving crop quality and yield. In this study, the effects of bioinoculants composed of Streptomyces costaricanus strain A-m1 on the properties, enzyme activity, and micro-organisms of soil in a tea garden and on the chemical composition and production of tea were investigated. The present results showed that the application of A-m1 bioinoculant could increase the activities of urease, protease and catalase, the content of alkali-hydrolyzable nitrogen, and the number of bacteria, fungi, and actinomycetes in tea garden soil. After application, the free amino acid content, 100-bud weight, and bud density of spring tea were also elevated. In the year of fertilization, the treatment composed of 70% bioinoculant + 30% chemical fertilizer showed the best effects on soil physical and chemical properties, enzyme activity, culturable microbial counts, and tea quality. A high ratio of organic to chemical fertilizer coapplication can significantly improve the growing conditions for tea plants, reduce the use of chemical fertilizers, improve the efficiency of nutrient utilization, and enhance both the yield and quality of tea. One year after fertilization, the 50% bioinoculant + 50% chemical fertilizer was more conducive to enhancing the quality of tea, while the 30% bioinoculant + 70% chemical fertilizer was more beneficial for improving the production of tea. A high ratio of chemical to bioinoculant coapplication is more favorable for maintaining high yield and quality in tea production, achieving healthy and sustainable tea garden management. The application of A-m1 bioinoculant will reduce the use of chemical fertilizers, improve the utilization efficiency of soil nutrients, and increase the production and quality of tea, contributing to the sustainable production of tea gardens. Full article