Search Results (709)

Extracellular polymeric substances (EPSs) produced by actinomycetes of the genus Rhodococcus play crucial roles in their ecological success, metabolic versatility, and biotechnological value. This review summarizes existing studies of Rhodococcus EPSs, emphasizing the biochemical composition, functional attributes, and practical significance of EPSs, as well as their importance in biomedicine, bioremediation, and other applications (food industry, biomineralization) with respect to the EPS chemical composition and biological roles. Rhodococcus species synthesize complex EPSs composed primarily of polysaccharides, proteins and lipids that, like in other bacteria, support cell adhesion, aggregation, biofilm formation, and horizontal gene transfer (and can prevent exogenous DNA binding) and are highly important for resistance against toxicants and dissolution/assimilation of hydrophobic compounds. EPSs produced by different species of Rhodococcus exhibit diverse structures (soluble EPSs, loosely bound and tightly bound fractions, capsules, linear and branched chains, amorphous coils, rigid helices, mushroom-like structures, extracellular matrix, and a fibrillar structure with a sheet-like texture), leading to variations in their properties (rheological features, viscosity, flocculation, sorption abilities, compression, DNA binding, and interaction with hydrophobic substrates). Notably, the EPSs exhibit marked emulsifying and flocculating properties, contributing to their recognized role in bioremediation. Furthermore, EPSs possess antiviral, antibiofilm, anti-inflammatory, and anti-proliferating activities and high viscosity, which are valuable in terms of biomedical and food applications. Despite extensive industrial and environmental interest, the molecular regulation, biosynthetic pathways, and structural diversity of Rhodococcus EPSs remain insufficiently characterized. Advancing our understanding of these biopolymers could expand new applications in biomedicine, bioremediation, and biotechnology. Full article

This study investigates the bacterial community structure and diversity across different root compartments (non-rhizosphere soil, rhizosphere soil, rhizosphere, and endosphere) of Camellia oleifera and their associations with three cultivars (‘Huashuo’, ‘Huajin’, ‘Huaxin’). High-throughput sequencing and bioinformatics analyses were performed to characterize the bacterial communities. A total of 22 phyla, 59 classes, 155 orders, 268 families, 523 genera, 929 species, and 2045 operational taxonomic units (OTUs) were identified. Alpha diversity indices (Shannon, Simpson, Chao1) showed no statistically significant differences among the three cultivars, but varied significantly across root compartments. The rhizosphere exhibited the highest bacterial diversity and richness, which was significantly higher than that in the endosphere. At the phylum level, Proteobacteria, Chloroflexi, Actinobacteriota, Acidobacteriota, Firmicutes, and Bacteroidetes dominated the communities. Significant differences were observed in the relative abundance of dominant genera (e.g., Proteus, actinomycetes) among varieties and root compartments. PCoA analysis revealed that ‘Huaxin’ had a distinct bacterial community structure compared to ‘Huashuo’ and ‘Huajin’, while the endosphere was separated from other compartments. Interaction network analysis indicated that most bacterial interactions were positive, with Colidextribacter, Uliginosibacterium, and Aliidongia showing the highest centrality, suggesting their key roles in maintaining community stability. This study provides novel insights into the distribution patterns and driving factors of root-associated bacteria in C. oleifera, laying a theoretical foundation for future research on disease control and quality improvement of this crop. Full article

Potato (Solanum tuberosum L.) is a key staple crop in the Peruvian Andes, but its productivity is threatened by fungal pathogens such as Rhizoctonia solani and Alternaria alternata. In this study, 71 native bacterial strains (39 from phyllosphere and 32 from rhizosphere) were isolated from potato plants across five agroecological zones of Peru and characterized for their plant growth-promoting (PGPR) and antagonistic traits. Actinomycetes demonstrated broader enzymatic profiles, with 2ACPP4 and 2ACPP8 showing high proteolytic (68.4%, 63.4%), lipolytic (59.5%, 60.6%), chitinolytic (32.7%, 35.5%) and amylolytic activity (76.3%, 71.5%). Strain 5ACPP5 (Streptomyces decoyicus) produced 42.8% chitinase and solubilized both dicalcium (120.6%) and tricalcium phosphate (122.3%). The highest IAA production was recorded in Bacillus strain 2BPP8 (95.4 µg/mL), while 5ACPP6 was the highest among Actinomycetes (83.4 µg/mL). Siderophore production was highest in 5ACPP5 (412.4%) and 2ACPP4 (406.8%). In vitro antagonism assays showed that 5ACPP5 inhibited R. solani and A. alternata by 86.4% and 68.9%, respectively, while Bacillus strain BPP4 reached 51.0% inhibition against A. alternata. In greenhouse trials, strain 4BPP8 significantly increased fresh tuber weight (11.91 g), while 5ACPP5 enhanced root biomass and reduced stem canker severity. Molecular identification confirmed BPP4 as Bacillus halotolerans and 5ACPP5 as Streptomyces decoyicus. These strains represent promising candidates for the development of bioinoculants for sustainable potato cultivation in Andean systems. Full article

Limited phosphorus (P) availability and declining soil biological health are major constraints in intensive rice (Oryza sativa L.)—wheat (Triticum aestivum L.) systems. Rock phosphate–enriched compost (REC), combined with microbial inoculants, offers a sustainable strategy for improving soil biological functioning. A field experiment was conducted under a randomized block design with seven treatments involving different combinations of REC, chemical fertilizers, phosphate-solubilizing bacteria (PSB), and arbuscular mycorrhizal fungi (AMF). Post-harvest soil samples from rice and wheat were analyzed for microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), enzymatic activities, microbial populations, root colonization, yield, and P uptake. The combined application of REC with PSB and AMF significantly enhanced soil biological parameters compared with recommended fertilizer doses. Under the REC + PSB + AMF treatment, dehydrogenase, acid phosphatase, and alkaline phosphatase activities increased by 77.4%, 24.8%, and 18.1%, respectively, while MBC and MBP improved by 51.6% and 106.6%. Bacteria, fungi, and actinomycete population increased by 55.0%, 76.7%, and 82.8%, respectively, as well as mycorrhizal root colonization increased by 18.7%. Grain yield of rice and wheat increased by 16% and 6%, respectively, along with higher P uptake. The integrated use of REC with PSB and AMF improved soil enzymatic activity, microbial biomass, and nutrient acquisition, leading to higher crop productivity. These results indicate that REC combined with PSB and AMF is an effective nutrient management strategy for improving soil biological health, P utilization, and crop productivity in rice–wheat systems. Full article

Cold-active lipolytic enzymes enable low-temperature biocatalysis, but remain underexplored in Antarctic actinomycetes. Here, we report the discovery and first-step characterization of a CALB-like cold-active lipolytic enzyme (PanLip) from Pseudonocardia antarctica. Sequence and structure analyses revealed a canonical α/β-hydrolase fold with a conserved Ser–Asp–His triad and short helical elements around the pocket reminiscent of CALB’s α5/α10 lid. Mature PanLip was expressed primarily as inclusion bodies in E. coli; an N-terminally truncation (PanLipΔN) improved solubility and PanLipΔN was purified by Ni–NTA. Far-UV CD confirmed a folded α/β architecture. PanLipΔN favored short-chain substrates (p-NPA, k_cat/K_M = 2.4 × 10⁵ M⁻¹·s⁻¹) but also showed measurable hydrolytic activity toward natural triglycerides, consistently with a lipase-family esterase. The enzyme showed an activity optimum near 25 °C and pH 8.0. The enzyme tolerated low salt (maximal at 0.1 M NaCl), mild glycerol, and selected organic solvents (notably n-hexane), but was inhibited by high salt, Triton X-100, and SDS. AlphaFold predicted high local confidence for the catalytic core; DALI placed PanLip closest to fungal lipases (AFLB/CALB). Temperature-series MD and CABS-flex indicated enhanced surface breathing and flexible segments adjacent to the active site—including a region topologically matching CALB α10—supporting a flexibility-assisted access mechanism at low temperature. Structure-based MSAs did not support a cold adaptation role for the reported VDLPGRS motif. Taken together, these findings position PanLip as a promising cold-active catalyst with CALB-like access control and potential for low-temperature biocatalysis. Full article

Mangrove forests represent a complex ecosystem inhabiting tropical and subtropical intertidal zones, harboring diverse microbial communities including fungi, actinomycetes, bacteria, cyanobacteria, algae, and protozoa. Among these communities, mangrove-derived fungi, as the second-largest ecological group of marine fungi, not only play essential roles in establishing and sustaining this biosphere but also serve as an important source of structurally unique and biologically active secondary metabolites. This review systematically summarizes research progress on metabolites isolated from mangrove-derived fungi and their associated bioactivities over the recent five years (2020–2025). Emphasis is placed on 457 metabolites documented in 97 selected publications, with a focus on the biological activities and distinctive chemical diversity of these secondary metabolites. This review provides an important reference for the research status of secondary metabolites isolated from mangrove-derived fungi and the lead compounds worthy of further development, and reveals that mangrove-derived fungi have important medicinal values and are worthy of further development. Full article

Foliar fertilization can influence soil health by altering soil physicochemical properties and nutrient cycling processes; however, its underlying mechanisms remain insufficiently understood. Here, we compared soils under two treatments—foliar fertilizer application (YMF) and no foliar fertilizer (CK)—and elucidated their effects on paddy soil health and associated microbial mechanisms. Comprehensive analyses of soil physicochemical properties, microbial diversity, and functional gene profiles were also conducted. We found that foliar fertilization enhanced soil physicochemical and biological properties, particularly pH, CEC, SOM, TN, AP, and MBC, resulting in an increase in the soil health index (SHI) from 0.805 to 0.906. Metagenomic analysis further revealed that foliar fertilization enriched functional microbial taxa such as Actinomycetes, Defluviilinea, Roseovarius, and Bradyrhizobium, which enhanced the activities of key nutrient cycling pathways, including carbon stabilization (K14469, MDH sdhB), nitrogen metabolism (narY, nxrA, hdh), and phosphorus mineralization (htxA, phnH). These findings provide mechanistic insights into the microbial processes underlying foliar fertilizer–induced improvement in soil health and offer theoretical support for the development of precision fertilization and sustainable soil health management strategies in agricultural systems. Full article

The use of mercury in industry causes its continuous increase in nature. A pro-ecological technology that can reduce mercury levels in aquatic environments is phytoremediation using the plant Salvinia natans. The study aimed to determine the maximum mercury concentration for effective phytoremediation using Salvinia natans. The study aimed to determine the threshold for effective phytoremediation using Salvinia natans. A Microtox screening test was performed for concentrations ranging from 0.15 to 0.50 mg Hg·L⁻¹. For the same concentrations, the effect of contamination on the physiological condition of the plant was tested by observing changes in the presence of chlorosis and necrosis. Analysis of enzymatic activity using the API ZYM test for plants exposed to mercury did not show any significant changes. The phytoremediation process produces a significant amount of spent phytoremediation biomass containing large amounts of mercury. Sustainable management in the form of a mixture with soil substrate, uncontaminated with mercury, was proposed. Microtox toxicity analysis of water extracts from soil containing biomass, with a final mercury content in the substrate of 1 mg Hg·kg⁻¹ of soil, showed no toxicity to the environment. However, microbiological analysis of the same soil substrate showed changes in the total number of bacteria, actinomycetes, fungi, moulds, and yeasts compared to the control samples. Full article

Rapid urbanisation and intensified poultry production have increased chicken feather waste (CFW), posing environmental concerns due to its recalcitrant keratin content. This study aimed to evaluate the potential of Actinomycetes, specifically Streptomyces sp., isolated from peat-rich soils, to degrade CFW and enhance nitrogen recovery. Chicken feathers collected from a slaughterhouse near Khulna University were washed, dried, ground, and inoculated with 2.5 mL of Streptomyces broth in a controlled composting setup. The decomposition process was monitored over eight days, with daily assessments of total and available nitrogen using the Micro-Kjeldahl method. The results demonstrated a significant increase (p ≤ 0.05) in nitrogen content in the Actinomycetes-treated decomposition group compared to the control. The highest total nitrogen content (6.43%) was observed on day 7, while peak available nitrogen (4.04%) occurred on day 8. The percentage of nitrogen recovery through Actinomycetes activity was 86.1%. These findings confirm the keratinolytic efficiency of Streptomyces in degrading feather waste and enhancing nitrogen mineralisation. Although nitrogen release was gradual, the resulting compost presents a viable slow-release organic fertiliser. This bioconversion approach offers an environmentally sustainable solution for poultry waste management and soil nutrient enrichment in agriculture. Full article

The actinobacterial strain Kitasatospora griseola JNUCC 62 was isolated from volcanic wetland soil at Mulyeongari Oreum, Jeju Island, and taxonomically identified through 16S rRNA gene and whole-genome analyses. The complete genome, assembled from PacBio Sequel I reads, spans 8.31 Mb with a GC content of 72.8% and contains 7265 coding sequences. Comparative genomic indices (Average nucleotide identity, ANI 97.46%; digital DNA–DNA hybridization, dDDH 84.4%) confirmed its conspecific relationship with K. griseola JCM 3339^T. Genome mining using antiSMASH 8.0 revealed 30 biosynthetic gene clusters (BGCs), including polyketide synthase (PKS), non-ribosomal peptide synthetase (NRPS), ribosomally synthesized and post-translationally modified peptide (RiPP), lanthipeptide, and terpene types, accounting for 18.6% of the genome. Several BGCs displayed homology to known formicamycin-, lankacidin-, and lanthipeptide-type clusters, while others were novel or cryptic, reflecting adaptation to the nutrient-poor volcanic environment. Ethyl acetate extraction of the culture broth, especially under tryptophan-supplemented conditions, yielded four metabolites—1-acetyl-β-carboline, perlolyrine, tryptopol, and 1H-pyrrole-2-carboxylic acid—identified by UV and NMR spectroscopy. These compounds correspond to NRPS–PKS hybrid and arylpolyene-type gene clusters predicted in the genome, suggesting precursor-directed biosynthesis of indole and pyrrole alkaloids. The ethyl acetate extract (JNUCC62 EA) exhibited strong antioxidant capacity in the ABTS assay, anti-inflammatory activity via inhibition of nitric oxide (31.09 ± 3.69% of control) and cytokines (IL-6, IL-1β, TNF-α) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, and anti-melanogenic effects in α-melanocyte-stimulating hormone (MSH)-stimulated B16F10 melanoma cells, where melanin content and tyrosinase activity decreased to 61.49 ± 1.24% and 24.32 ± 0.31% of the control, respectively, without cytotoxicity. A human primary skin irritation test confirmed no irritation up to 50 µg/mL, establishing excellent dermal safety. Collectively, these findings highlight K. griseola JNUCC 62 from Mulyeongari Oreum as a volcanic wetland-derived actinomycete harboring rich biosynthetic potential for novel indole alkaloids with antioxidant, anti-inflammatory, and whitening properties, supporting its development as a safe and multifunctional cosmeceutical ingredient. Full article

Understory vegetation is a critical component of forest ecosystems. Its removal can substantially alter litter decomposition processes, with cascading effects on carbon (C) and nutrient cycling in terrestrial ecosystems. However, the global response patterns of litter decomposition to understory removal and underlying controlling factors remain unclear. We conducted a meta-analysis of 330 observations from 29 peer-reviewed field litterbag studies to assess the effects of understory removal on litter decomposition. We evaluated the changes in decomposition rate, mass loss, and nutrient dynamics to quantify the impacts of understory removal on litter decomposition. We assessed the associated shifts in soil microbial communities, measured using phospholipid fatty acids (PLFAs), to examine how microbial responses mediate decomposition during understory removal. We examined whether canopy type moderated these responses and explored the key predictors of decomposition for understory removal. Understory removal significantly reduced litter decomposition rate and mass loss by an average of 29.6% and 14.8%, respectively, while increasing lignin remaining by 30.1%. Soil microbial biomass also declined, with total, fungal, and actinomycete PLFAs decreasing by 12.0%, 30.8%, and 27.5%, respectively. Across canopy types, understory removal decreased litter mass loss in both broadleaved and coniferous forests. However, the remaining N and P increased significantly in broadleaved forests but changed only marginally in coniferous forests. Random forest analysis showed that initial litter quality and variations in fungal biomass were the primary predictors of decomposition responses. Understory vegetation removal significantly suppresses litter decomposition by reducing fungal biomass, and interacting with litter quality constraints and canopy type strongly moderates these effects. This highlights the essential role of understory vegetation in sustaining nutrient cycling and microbial functioning in forest ecosystems and underscores its critical role in guiding sustainable forest management. Full article

The genus Actinokineospora (family Pseudonocardiaceae) has recently emerged as a prolific source of structurally diverse, biologically active specialized metabolites. Actinokineospora spp. are filamentous actinomycetes isolated from various terrestrial biotopes. The genus is still sparsely represented taxonomically, with only 19 species holding validly published names and genome sequences available for an additional six strains. Nevertheless, Actinokineospora appears to have one of the highest biosynthetic novelty index values among actinomycetes, making it a prime candidate for the discovery of new specialized metabolites. To date, several Actinokineospora strains have shown antimicrobial activity, including Actinokineospora acnipugnans R434^T, Actinokineospora alba 03-9939^T, Actinokineospora fastidiosa NRRL B-16697^T, Actinokineospora riparia C-39162^T, Actinokineospora sp. G85, and Actinokineospora sp. PR83; the active compounds from these strains remain to be identified and characterized. By contrast, detailed chemical characterization has been achieved for several producers: Actinokineospora spheciospongiae EG49^T (polyketides actinospene and actinosporins; the lasso peptide actinokineosin), Actinokineospora bangkokensis 44EHW^T (polyene thailandins), Actinokineospora fastidiosa ATCC 202099 (nocathiacin thiopeptides), Actinokineospora sp. UTMC 2448 (persiathiacin thiopeptides), and Actinokineospora auranticolor DSM 44650^T (kineomіcin glycopeptides). Collectively, these findings establish Actinokineospora as a promising yet underexplored genus for antibiotic discovery and biosynthetic engineering. In this review, we summarize current knowledge on Actinokineospora spp. and provide an in-depth account of specialized metabolite production for those compounds whose structures have been elucidated. Full article

The physicochemical properties of soil have a significant impact on plant growth, and fertilizers that improve soil quality play a crucial role in promoting crop development. Abandoned crop straw, once composted and converted into organic fertilizer, is an important resource for agricultural production. However, the mechanisms by which straw compost regulates plant growth remain incompletely understood. In previous work, we demonstrated that low-temperature-fermented straw compost significantly promoted the growth and yield of rice. To further investigate the effects of low-temperature-fermented straw compost on alfalfa growth, this study incorporated 10% and 30% straw compost into soil for alfalfa cultivation and systematically compared plant growth and soil quality indicators. Results showed that compost application increased alfalfa leaf length by 30.55%, with significant improvements observed in multiple physiological parameters. Furthermore, straw compost amendment raised soil pH to 6.88, substantially enhanced soil organic matter content, and increased the activities of sucrase and urease by approximately 181.77% and 223.81%. The abundance of soil microorganisms, including fungi and actinomycetes, increased by approximately 129.59% and 444.44%, respectively, indicating that straw compost effectively improves soil conditions and promotes alfalfa growth. Overall, the study demonstrates that low-temperature-fermented straw compost exerts a promoting effect on crop growth and provides an important theoretical basis for promoting low-temperature straw fermentation technology and the application of straw composting in agricultural and animal husbandry production. Full article

To address soil degradation from long-term monoculture, rotary tillage, and excessive chemical fertilization in semi-arid regions of China, we conducted a three-year field experiment. We assessed the synergy of integrated management practices combined with both continuous and rotational tillage methods (including ploughing, rotary, moldboard ploughing) at varying tillage depths (10–15, 15–25, 25–35 cm) with different fertilization regimes (chemical vs. organic–inorganic). Among all treatments, the rotational tillage practice that integrates moldboard ploughing at 25–35 cm depth with organic–inorganic fertilization [1200 kg ha⁻¹ mature compost + 375 kg ha⁻¹ compound fertilizer (N:P₂O₅:K₂O = 15:15:15)] significantly reduces bulk density by 11.8% and increases total porosity by 17.9% in the 15–25 cm soil layer. This practice optimizes nutrient stratification, elevating available nitrogen and potassium in the shallow layer (10–15 cm) to 126.13 and 372.45 mg kg⁻¹, respectively, while boosting available phosphorus in the subsoil (25–35 cm) by 247.8%. Furthermore, it significantly enhances soil microbial activity, increasing populations of bacteria, actinomycetes, and fungi by 3.42 × 10⁵, 0.65 × 10⁵, and 2.40 × 10³ CFU g⁻¹, respectively, alongside a 49.4% rise in soil respiration. These synergistic improvements collectively promote stable maize yields (increasing by 1731.4 kg ha⁻¹) and high economic returns (net income increasing by 3301.6 CNY ha⁻¹). These findings support the promotion of integrated tillage–fertilization strategies to enhance maize productivity and soil ecological function in semi-arid regions. Full article

Nitrogen is an essential element required for bacterial homeostasis. It serves as a building block for the biosynthesis of macromolecules and provides precursors for secondary metabolites. Actinomycetes have developed the ability to use various nitrogen sources to ensure their survival in ecological niches with fluctuating nutrient availability. A complex nitrogen metabolism of Actinobacteria allows the utilization of various compounds as N sources, including ammonium, nitrate, urea, amino acids, amino sugars, and amines. One such adaptation is the ability to acquire nitrogen from alternative amine sources like monoamines or polyamines putrescine, cadaverine, spermidine, and spermine, ensuring both nutrient availability (C and N sources) and resistance against high polyamine concentrations. Actinobacterial nitrogen degradation, including the catabolism of amines, is not only important under low nitrogen availability, but also required to survive under high concentrations of these compounds. The purpose of this review is to summarize the knowledge on nitrogen degradation and, more specifically, catabolism of amines in Actinobacterial survival and its role in nitrogen metabolism. Applying critical analysis of the recent available literature and sequencing data, this work aims to explore strategies of pathogenic and non-pathogenic Actinobacteria to survive in the presence of different nitrogen sources, and their impact on primary and secondary metabolism. The knowledge about nitrogen degradation pathways in Actinobacteria including mono- and polyamine catabolism collected in the scope of this review paper is brought in connection with possibilities to combat pathogens by using their capability to metabolize polyamines as an antibiotic drug target. This might offer new directions for target-based drug design to combat Actinobacterial infections. Full article