Environmental pollution caused by crude oil contamination poses a major ecological threat, highlighting the need for sustainable bioremediation approaches. Biosurfactants produced by actinobacteria offer promising advantages due to their eco-friendly and multifunctional properties. In this study, soil samples were collected from oil contaminated sites in and around Salem, Tamil Nadu, India. Eight morphologically distinct isolates were screened based on β-hemolysis, oil displacement, emulsification index, and lipase activity. Among them, strain AS1 demonstrated the highest biosurfactant activity. Molecular identification through 16S rRNA gene sequencing confirmed that AS1 belongs to the genus Streptomyces and submitted to GenBank with an accession number-MT525319. The potent strain exhibited strong crude oil degradation capabilities, achieving 95.9% degradation after 168h as determined by hydrocarbon utilization tests, DCPIP assay, and gravimetric analysis. The biosurfactant extracted from strain AS1 showed notable antibacterial activity against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli, with low minimum inhibitory concentrations, and demonstrated considerable antioxidant potential with 70.04% DPPH radical scavenging activity at 500µg/ml. Purification by dialysis yielded a partially purified biosurfactant that was characterized by TLC, FT-IR, and GC-MS analyses. FT-IR spectra revealed the presence of functional groups such as alkanes and carboxylic acids, while GC-MS identified several bioactive compounds, including 1-tetradecanol and phthalic acid derivatives. These findings suggest that Streptomyces sp. AS1 strain is a promising candidate for crude oil bioremediation and the development of biosurfactant based applications in pharmaceutical and environmental industries.

Actinobacteria are Gram-positive bacteria found mainly in soil and notable for their ability to produce hydrolytic enzymes and cellular amidase. They are widely recognized for their ability to produce secondary metabolites with high biotechnological relevance, including antibiotics, enzymes, and compounds with antifungal and antitumor activity. Due to the growing demand for new bioactive agents, especially in the face of microbial resistance, extreme and impacted environments have been explored as promising sources for the isolation of microbial strains adapted to adverse conditions. In this context, the present study aimed to isolate and characterize actinobacteria present in soil impacted by municipal solid waste in the municipality of Pinheiro-MA, in addition to evaluating their antagonistic capacity against pathogenic microorganisms. From serial dilutions and cultivation in selective medium, colonies with morphology typical of the genus Streptomyces spp. were obtained, with filamentous growth, velvety texture, and variable pigmentation. Macroscopic and microscopic identification reinforced the presence of structures compatible with Gram-positive actinobacteria. In the antagonism test, no inhibition halo was observed, showing no antagonistic activity for the tested strains of Pseudomonas, Staphylococcus, E. coli, and Candida albicans ATCC 14053 and TCC 1884. The results point to landfill soil as a promising reservoir of microorganisms adapted to extreme conditions, with biotechnological potential for the prospecting of antibiotics and industrial enzymes.

The genus Streptomyces is the largest group within the phylum Actinobacteria, recognized for producing antibiotics and enzymes, with wide applications in medicine and biological control for crop protection against phytopathogens. In this study, the Streptomyces sp. Caat 5-35 strain, isolated from soil of the Caatinga biome in Brazil, and identified by analysis of the 16S rRNA gene, demonstrated its antagonistic effect in vitro in dual cultures against Phytophthora palmivora, Colletotrichum acutatum, Fusarium oxysporum, Rhizoctonia solani, Sclerotinia sclerotiorum, and Fusarium graminearum. Caat 5-35 inhibited mycelial growth ranging from 19% to 73.3%. Compounds purified by prep-HPLC from extracts were identified by spectral data analysis using UHPLC-triple-TOF-MS/MS, or nuclear magnetic resonance (NMR). This work demonstrated for the first time the anti-oomycete activity of albofungin, its derivatives, and albonoursin against P. palmivora. Moreover, the growth inhibition of Colletotrichum gloeosporioides by albonoursin and the antibacterial effect of 2-chloroadenosine and 5′-O-sulfamoyl-2-chloroadenosine against Pectobacterium carotovorum were demonstrated as novel findings. Caat 5-35 exhibited the ability to solubilize phosphates and produce cellulases on CMC agar. The findings of this study, in combination with in vitro bioassays on cacao pods (Theobroma cacao L.) inoculated with the antagonist strain and P. palmivora APB-35, demonstrate that Streptomyces sp. Caat 5-35 is a source of natural products with applications in agriculture and could serve as an alternative for crop protection.

The freshwater snail Cipangopaludina lecythis holds both ecological and medicinal importance, yet its microbiome remains unexplored. This study presents the first shotgun metagenomic profiling of edible tissues of C. lecythis. Illumina HiSeq sequencing generated over 42 million high-quality reads, revealing 38 bacterial phyla dominated by Pseudomonadota (32%), followed by Bacillota and Actinomycetota. At the genus level, Pseudomonas, Klebsiella, Acinetobacter, Bacillus, Clostridium, Staphylococcus, and Streptomyces were prevalent. Functionally important genera such as Aeromonas, Vibrio, and Pseudoalteromonas which are known for their probiotic and immunomodulatory properties were also detected. The dominant species included Pseudomonas sp. REST10, Escherichia coli, Klebsiella pneumoniae, and Streptomyces sp. T12, many of which were associated with fermentation and host microbe interactions. Interestingly, the microbial profiles differed from those in marine snails, indicating environment-specific microbiome signatures. Functional annotation revealed key enzymes including 17 beta-hydroxysteroid dehydrogenase type 3 (HSD17B3) and malonyl-CoA:ACP transacylase, involved in fatty acid metabolism and energy regulation. Enzymes such as glutathione S-transferase and arylacetamide deacetylase were also detected, along with chitinase and chitin synthases, suggesting host microbe interactions in chitin metabolism. High alpha diversity showed a rich and functional microbiome. Overall, this study highlights the metabolic potential and ecological relevance of the C. lecythis microbiome, supporting its application in biotechnology and nutraceutical industry.

Strain HK10T, previously isolated from saltern sediment and identified as a salternamides-producing bacterium, was taxonomically characterized in the present study. The strain is a Gram-stain-positive, aerobic, and filamentous actinobacterium. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain HK10T belongs to the genus Streptomyces and is most closely related to Streptomyces radiopugnans R97T (99.4% sequence similarity), followed by other Streptomyces species with sequence similarities of ≤98.9%. The draft genome sequence of strain HK10T was 6.69 Mbp and a DNA G+C content of 72.7%. Average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain HK10T and type strains of the genus Streptomyces were ≤92.7% and ≤53.0%, respectively, which are below the thresholds for species delineation, indicating that strain HK10T represents a novel species. The major cellular fatty acids were iso-C16:0, anteiso-C15:0, anteiso-C17:0, and iso-C14:0. The predominant menaquinone was menaquinone-9 (MK-9). The polar lipid profile included phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylinositol dimannoside. Whole-cell hydrolysates of strain HK10T contained L,L-diaminopimelic acid and glycine. Based on phylogenetic, genomic, chemotaxonomic, and physiological evidence, strain HK10T is considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces shinuiensis sp. nov. is proposed. The type of strain is HK10T (= NBRC 114904T = KACC 22137T).

Streptomyces specialized metabolites account for over half of all clinically used antibiotics, as well as numerous antifungal, anticancer, and immunosuppressant agents. Two-component systems, which are widespread in bacteria, are key regulators of antibiotic production in Streptomyces species, yet their activating signals remain poorly understood. CutRS was the first two-component system identified in the genus Streptomyces, and deletion of cutRS in Streptomyces coelicolor was shown to enhance antibiotic production, although its CutR regulon does not include biosynthetic genes. Here, we used Streptomyces venezuelae NRRL B-65442 to further investigate CutRS function. We show that deletion of cutRS increases growth rate and a reversal of the glucose-mediated carbon catabolite repression typically observed in Streptomyces species. We also demonstrate that CutR DNA binding is glucose-dependent, but CutR does not directly regulate genes involved in growth, antibiotic biosynthesis, or glucose metabolism. The only CutR targets conserved in both S. coelicolor and S. venezuelae are the foldase genes htrA3 and htrB, which are involved in the protein secretion stress response. Consistent with this, we show that CutS homologs all contain two conserved cysteine residues in their extracellular sensor domains and that changing these residues to serine constitutively activates S. venezuelae CutRS. We propose that failure of a disulfide bond to form between these cysteine residues indicates secretion stress and leads to activation of the CutRS system and the secretion stress response.IMPORTANCEStreptomyces bacteria are the primary source of clinically useful antibiotics. While many two-component systems have been linked to antibiotic biosynthesis in Streptomyces species, few have been well characterized. Here, we characterize a secretion stress-sensing two-component system called CutRS and propose a model for how the sensor kinase detects extracellular protein misfolding via two highly conserved cysteine residues. Importantly, we also show that deletion of cutRS triggers antibiotic overproduction in the presence of glucose. Since glucose normally represses antibiotic biosynthesis in Streptomyces species through carbon catabolite repression, this finding reveals a simple genetic route to bypass this barrier. This has significant implications for antibiotic discovery pipelines and industrial production, where glucose-rich media are preferred for cost and scalability. Our results position CutRS as a key target for future strain-improvement strategies.

This study characterized three bacterial endophytes isolated from healthy Eucalyptus camaldulensis trees in Tehran, Qom, and Mazandaran provinces of Iran. 16S rRNA sequencing identified all isolates as Streptomyces genus. Their antifungal potential was evaluated against four tomato pathogens: Botrytis cinerea, Fusarium oxysporum f. sp. lycopersici, Macrophomina phaseolina, and Rhizoctonia solani. Dual-culture assays revealed strong antagonistic activity, with inhibition rates ranging from 59% to 95% against most pathogens. However, Streptomyces sp. 3L3 showed no activity against R. solani. In volatile organic compound assays, all strains suppressed B. cinerea, while Streptomyces sp. 3L3 additionally inhibited F. oxysporum f. sp. lycopersici. In contrast, no antagonistic activity was observed against the other tested pathogens. Enzymatic assays confirmed cellulase and chitinase production in all strains, suggesting potential antagonistic mechanisms, though phosphate solubilization capacity was absent. In greenhouse experiments on tomato plants, the dual effects of pathogen control and plant growth promotion was evaluated. Among the tested strains, Streptomyces sp. QS4 exhibited the highest inhibition rate against all pathogens, except for B. cinerea, which was most strongly suppressed by Streptomyces sp. GL4. Additionally, plants inoculated with both endophytes and pathogens showed significantly less growth reduction compared to pathogen-only controls. Gas chromatography-mass spectrometry analysis identified several bioactive metabolites in the three bacterial strains, with hexadecanoic acid, di-(2-ethylhexyl)phthalate, and tetradecanoic acid being the most abundant compounds, all known to contribute to biocontrol and plant growth modulation. These findings demonstrate that the Streptomyces endophytes exhibit significant antifungal activity through multiple mechanisms, underscoring their potential as biocontrol agents.

Plant microbiota has received increasing attention in recent years. In particular, the microbiota associated with cereals is being extensively studied to identify bacterial strains that can promote plant health and growth. Barley is the fourth most important cereal worldwide in terms of agricultural production. Intensive barley agriculture requires the use of chemical fertilizers to compensate for nutrient deficiencies in soils and limit pathogen development. The isolation and use of bacteria that can enhance the bioavailability of soil nutrients and inhibit the development of plant pathogens could ultimately limit the use of these chemicals. In this study, we have isolated from a barley microbiota three bacterial strains belonging to the genus Streptomyces. These strains were characterized and named GPA1, GPAT2, and GPN2. These three closely related isolates were from the same bacterial genus Streptomyces. Based on a phylogenetic analysis, the strains GPAT2 and GPN2 were classified as Streptomyces murinus, while GPA1 was identified as a new species. All strains showed antagonistic activity against two microorganisms that inhibit barley germination: Pseudomonas sp. MRN1 and Fusarium sp. CK. In addition, these strains exhibited different effects on the growth of barley cultivated under hydroponic and axenic conditions. In fact, GPN2 appeared to have no effect whereas the inoculation of barley seedlings with GPAT2 and GPA1 resulted in a reduction and an increase in root length after two weeks of growth, respectively. GPA1 had various Plant Growth-Promoting (PGP) abilities, including phosphate and zinc solubilization and siderophore production. A metabolite profiling of the GPA1 bacterial culture also showed its production and excretion of indole-3-acetic acid (IAA). In this study, we have characterized three closely related bacteria, which display different effects on barley seedlings growth. These results revealed that the type of interactions of Streptomyces with barley is strain-dependent, suggesting that these interactions may arise from specific molecular mechanisms acquired through coevolutionary processes.

Bacterial isolate with glucose isomerase-producing ability was obtained from garden soil by means of starch casein agar as a selective medium. Morphological and microscopic analyses suggested the isolate belonged to the Streptomyces genus, and its identity was further confirmed as Streptomyces roseiscleroticus through 16S rRNA gene sequencing. The glucose isomerase production potential of the isolated strain was evaluated by employing 2, 3, 5-triphenyltetrazolium solution as a color-indicating agent. Optimization studies revealed that optimum glucose isomerase production was obtained at 37 oC and pH 7.0 after 120 hours of submerged fermentation. Significant enhancement in glucose isomerase production was observed with xylose (67.7 ± 2.00) as the preferred carbon source, a blended nitrogen source comprising peptone, beef extract, and yeast extract (36.7 ± 1.80), and tetra trimethyl ammonium bromide (67.7 ± 2.00) as the detergent facilitating enzyme extraction. The results imply that Streptomyces roseiscleroticus holds promise as a microbial source for industrial-scale glucose isomerase production, with potential applications in the manufacturing of high-fructose corn syrup (HFCS) as a sweetener and bioethanol as a renewable fuel.

9-Methylstreptimidone: A novel promising fungicide disrupting material metabolism and energy synthesis in Colletotrichum orbiculare.

BackgroundFeather waste, a byproduct of the poultry industry, remains underutilized due to its recalcitrant nature. While microbial conversion holds substantial potential, the scarcity of high-efficiency degrading strains hampers industrial application.ResultsA novel feather-degrading actinobacterium, designated KKT, exhibited highly efficient decomposition of feather waste. When cultured with 10% (w/v) chicken feathers as sole nutrient source, it achieved over 50% degradation within 8 days. Taxonomic characterization identified strain KKT as a novel species of the genus Streptomyces, with the proposed name Streptomyces shaoguanensis sp. nov.. Genomic analysis of strain KKT revealed an abundance of functionally uncharacterized genetic elements and 26 predicted biosynthetic gene clusters (BGCs) for secondary metabolites. Integrated transcriptomic and biochemical analyses suggested that feather degradation by S. shaoguanensis KKT represents an adaptive physiological response. This process was found to sustain an alkaline fermentation environment through continuous ammonia release and to efficiently disrupt disulfide bonds via a non-sulfite-dependent mechanism mediated by cysteine, H₂S and reductases. Simultaneously, highly efficient degradation was achieved through the temporally coordinated action of multiple proteases. Furthermore, when applied as a biofertilizer, the feather hydrolysate significantly promoted the growth of Brassica rapa subsp. chinensis (Pak Choi) compared to commercial amino acid fertilizers, achieving 13.1% higher fresh weight, 14.4% greater leaf area, 16.3% increased chlorophyll content, and 45.3% elevated soluble protein levels.ConclusionsHere, a novel Streptomyces species strain KKT with superior feather-degrading efficiency was reported. A wealth of functionally uncharacterized genes and significant biosynthetic potential in the genome of strain KKT laid a genetic groundwork for the exploration of its novel physiological functions and the discovery of uncharacterized metabolites. Integrative analyses of genomics, transcriptomics, and biochemical profiles of the degradation metabolites, together, uncovered the underlying mechanism of superior feather-degrading capacity. Additionally, the feather hydrolysate demonstrated a significant growth-promoting effect on Pak Choi. This finding provides a solid foundation for the sustainable valorization of feather waste and the development of novel biofertilizers.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12934-025-02878-8.

Eucalyptus is an economic plant of Thailand that can tolerate salt and drought stress. This work aims to report on the study of biodiversity among endophytic actinobacteria isolated from Eucalyptus camaldulensis grown in saline soil, as well as their properties for promoting plant growth and inhibiting fungal pathogens in vitro. Root, twig, and leaf samples of five plants, E. camaldulensis grown in Kalasin Province, Thailand, were collected. The soil samples of each plant were collected, and soil salinity was evaluated by the electrical conductivity of a saturated soil extract (ECe). It was found that the ECe of the soil was between 4.5 and 12 dS/m, and the pH of the soil ranged between 3.9 and 5.2. Based on their morphology and 16S rRNA gene sequences, the majority of the isolates (552, 96.7%) were identified as the genus Streptomyces. The remaining isolates (19, 3.3%), which included ten genera: Cellulosimicrobium (3), Kocuria (3), Brevibacterium (2), Micrococcus (2), Microbacterium (2), Peterkaempfera (2), Tsukamurella (2), Brachybacterium (1), Curtobacterium (1), and Gordonia (1). Two hundred and seventy-three isolates were tested for antifungal activity against two eucalyptus pathogens, Pseudoplagiostroma eucalypti LS6 and Cladosporium sp. LB1. Most isolates showed antifungal activity against P. eucalypti LS6. The plant growth-promoting (PGP) study of 154 selected strains showed that 154 (100%), 18 (11.7%), 14 (9.1%), and 7 (4.5%) isolates could produce indole-3-acetic acid (IAA), 1-aminocyclopropane (ACC) deaminase, solubilize phosphate, and fix nitrogen in vitro, respectively. Identification of non-actinobacteria isolates based on 16S rRNA gene sequence analysis indicated that 10 genera were obtained: Aureimonas, Bacillus, Chryseobacterium, Deinococcus, Massilia, Methylobacterium, Pseudomonas, Serratia, Staphylococcus, and Stenotrophomonas. One selected Streptomyces strain, EWL5.1, was selected for a seed germination test in salinity stress and PGP in planta. The result indicated that this strain could support the seedling length vigor index (SLVI) of eucalyptus seedlings in salinity conditions and significantly increase the fresh weight of eucalyptus seedlings in planta. Four representative Streptomyces strains and one strain of Micrococcus were sequenced for their genomes. The result indicated that these four Streptomyces strains comprise various biosynthesis gene clusters (BGCs) of antibiotic production. Genome data mining also reveals that all strains contain genes encoding PGP properties. These potential strains can be applied to be used as PGPB to support eucalyptus growth in the future.

The genus Streptomyces has consistently been found enriched in drought-stressed plant root microbiomes, yet the ecological basis and functional variation underlying this enrichment at the strain and isolate level remain unclear. Using two 16S rRNA sequencing methods with different levels of taxonomic resolution, we confirmed drought-associated enrichment (DE) of Streptomyces in field-grown sorghum roots and identified five closely related but distinct amplicon sequence variants (ASVs) belonging to the genus with variable drought enrichment patterns. From a culture collection of sorghum root endophytes, we selected 12 Streptomyces isolates representing these ASVs for phenotypic and genomic characterization. Whole-genome sequencing revealed substantial variation in gene content, even among closely related isolates, and exometabolomic profiling showed distinct metabolic responses to media supplemented with drought- versus well-watered root tissue. Traits linked to drought survival, including osmotic stress tolerance, siderophore production, and carbon utilization, varied widely among isolates and were not phylogenetically conserved. Using a broader panel of 48 Streptomyces, we demonstrate that DE scores, determined through mono-association experiments in gnotobiotic sorghum systems, showed high variability and lacked correlation with plant growth promotion. Pangenome-wide association identified orthogroups involved in osmolyte transport (e.g., proP) and membrane biosynthesis (e.g., fabG) as positively associated with DE, though most associations lacked phylogenetic signal. Collectively, these results demonstrate that Streptomyces DE is not a conserved genus-level trait but is instead strain-specific and functionally heterogeneous. Furthermore, DE in the root microbiome was shown not to predict beneficial effects on plant growth. This work underscores the need to resolve functional traits at the strain level and highlights the complexity of microbe-host-environment interactions under abiotic stress.

The genus Streptomyces has consistently been found enriched in drought-stressed plant root microbiomes, yet the ecological basis and functional variation underlying this enrichment at the strain and isolate level remain unclear. Using two 16S rRNA sequencing methods with different levels of taxonomic resolution, we confirmed drought-associated enrichment (DE) of Streptomyces in field-grown sorghum roots and identified five closely related but distinct amplicon sequence variants (ASVs) belonging to the genus with variable drought enrichment patterns. From a culture collection of sorghum root endophytes, we selected 12 Streptomyces isolates representing these ASVs for phenotypic and genomic characterization. Whole-genome sequencing revealed substantial variation in gene content, even among closely related isolates, and exometabolomic profiling showed distinct metabolic responses to media supplemented with drought- versus well-watered root tissue. Traits linked to drought survival, including osmotic stress tolerance, siderophore production, and carbon utilization, varied widely among isolates and were not phylogenetically conserved. Using a broader panel of 48 Streptomyces, we demonstrate that DE scores, determined through mono-association experiments in gnotobiotic sorghum systems, showed high variability and lacked correlation with plant growth promotion. Pangenome-wide association identified orthogroups involved in osmolyte transport (e.g., proP) and membrane biosynthesis (e.g., fabG) as positively associated with DE, though most associations lacked phylogenetic signal. Collectively, these results demonstrate that Streptomyces DE is not a conserved genus-level trait but is instead strain-specific and functionally heterogeneous. Furthermore, DE in the root microbiome was shown not to predict beneficial effects on plant growth. This work underscores the need to resolve functional traits at the strain level and highlights the complexity of microbe-host-environment interactions under abiotic stress.

This review aimed to thoroughly investigate the changing traits, ecological roles, and current studies pertaining to the soil-dwelling bacteria of the genus Streptomyces, which morphologically resemble fungi. These gram-positive bacteria exhibit a filamentous structure and are found in diverse environments, including various types of soil, compost, water, and plant matter. A defining feature of Streptomyces is their capacity to synthesize secondary metabolites, particularly antibiotics. They are responsible for producing more than two-thirds of the clinically relevant antimicrobials derived from natural sources, such as chloramphenicol, neomycin, etc. Streptomyces are noted for their broad substrate with branches and aerial mycelium. Factors such as carbon and nitrogen sources, oxygen levels, acidity or alkalinity, temperature, ions, and certain precursors can influence antibiotic production. This review also explored different approaches for evaluating the antimicrobial characteristics of Streptomyces species. The increasing problem of microbial resistance to traditional antibiotics, along with the difficulties in controlling infectious diseases, has prompted continuous global initiatives to identify new antibiotics.

Advancing microbial bioprospecting is crucial for discovering novel sources of antimicrobial compounds (ACs). Members of the phylum Actinomycetota, particularly the genus Streptomyces, are renowned producers of a wide variety of bioactive metabolites, including several clinically relevant antibiotics. In the present study, 182 Brazilian actinomycete strains were screened for antimicrobial activity against major human pathogens, namely Staphylococcus aureus MRSA BMB9393, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 11229, Aspergillus niger ATCC 16404, Candida albicans ATCC 10231, and Cryptococcus neoformans T1444. Among these, strain AM6-12 exhibited strong and broad-spectrum inhibitory activity. To optimize its metabolite production, AM6-12 was grown in various media (ISP-1, ISP-2, Mueller-Hinton, and glycerol-peptone broth) under submerged fermentation at 28°C for 12days. Supernatants were collected through centrifugation and filtration and tested via disk diffusion with 100, 150, and 200μL volumes. Inhibition zones were measured after 36h at 35°C. Further experiments in ISP-2 medium under varying aeration conditions (180 vs. 210rpm; different flask volumes) showed improved activity at 180rpm, notably against MRSA (2.6cm) and P. aeruginosa (1.25cm), indicating oxygen availability influences metabolite synthesis. Genomic sequencing revealed a 7.88Mb genome with a G + C content of 72.0mol%. The 16S rRNA gene shared 100% identity with Streptomyces malaysiense MUSC 136, but multilocus sequence analysis (MLSA) of 16S rRNA, atpD, gyrB, rpoB, recA, and trpB showed divergence above the species threshold (MLSA distance > 0.007). Additionally, ANI (< 95%) and digital DNA-DNA hybridization (dDDH < 70%) supported its classification as a distinct species. These findings position AM6-12 as a promising novel Streptomyces species for antimicrobial production.

Antibiotic-resistance is growing around the world and is now a serious health concern. It is thus essential to find novel, extremely potent antibiotics. The Streptomyces genus has attracted the attention of researchers worldwide because it is the most well-known producer of antibiotics. This study aimed to isolate Streptomyces strains from the Jordan Valley soil and evaluate their ability to produce bioactive substances. Twenty bacterial strains were isolated, and the antimicrobial activity was performed against five types of pathogenic bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa) using the modified cross-streak method for primary screening and the agar diffusion assay for secondary screening. One isolate, the SR2 strain, showed the highest bioactivity in the primary and secondary screenings against two pathogenic bacteria (B. subtilis and P. aeruginosa). It caused zones of inhibition of about 17–28 mm at 500 µg disc-1. Therefore, this bacterial strain was selected for further studies. 16S rDNA sequencing was used to identify the SR2 strain. The identification findings revealed a 98% similarity to Streptomyces labedae. Overall, this study demonstrated that Streptomyces labedae SR2 isolated from Jordan Valley soil has the potential to produce effective antimicrobial compounds against both Gram-positive and Gram-negative pathogenic bacteria.

Morels are a rare edible and medicinal fungus. A major factor contributing to difficulties with their continuous cropping is alteration in soil microbial communities. Pseudomonas putida is a key microorganism in morel cultivation soils; it has garnered significant attention due to its ability to degrade 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene. However, the interaction between Pseudomonas putida and morels remains unclear. This study evaluated the growth-promoting potential of P. putida KT2440 by measuring the casing soil ACC content and assessing its ACC utilization capacity. Metagenomic sequencing was performed to assess the changes in soil microbial composition and function. The results indicated that ACC accumulated in the soil following morel cultivation and that P. putida KT2440 was capable of utilizing ACC as its sole nitrogen source for growth on plates. Inoculation enhanced the depletion of available nitrogen, phosphorus, and potassium; increased bacterial diversity; improved the stability of the soil microbial community; and caused the mycelium of morels to grow earlier. These processes occurred along with a decline in the abundance of the Streptomyces genus. Furthermore, a positive correlation was identified between the abundance of P. putida and ACC deaminase activity in the soil. Overall, this study examined the role of Pseudomonas putida inoculation in modulating the soil microbial community and metabolic processes within casing soil during Morchella sextelata cultivation. The findings indicate that P. putida inoculation promotes Morchella growth through ACC decomposition and microbial restructuring, offering a potential strategy for mitigating ethylene-related suppression in continuous cropping systems.

In the arid regions of southern Tunisia, soil and irrigation water salinity represent major challenges to agricultural sustainability. Despite the increasing interest in plant-associated microbes, the role of endophytic bacteria in conferring salt tolerance remains largely unexplored in this context. To address this gap, twenty-two halophytic plants and their associated soils were sampled from five distinct sites across the Kebili and Gabes governorates. Significant differences in soil physicochemical properties were observed between sampling sites. The soils are generally poorly developed, non-fertile (with very low organic matter and high CaCO3 levels), and highly saline, leading to limited cultivation potential. Molecular identification of plants revealed nine different families and 14 genera, with the Amaranthaceae family being the most prominent, including Atriplex spp. (2), Bassia spp. (2), Suaeda spp. (4), and Halocnemum spp. (1). Bacterial community studies were conducted of both culturable and non-culturable endophyte communities inhabiting the green and root compartments of different halotolerant plants. Endophytic microbiome compositions differed between above-ground and below-ground tissues within the same plant family. A higher prevalence of three phyla Proteobacteria (67.80%), Firmicutes (14.06%), and Actinobacteria (6.57%) was detected across all samples. At the genus level, Acinetobacter, Halomonas, Kushneria, Pseudomonas, Psychrobacter, Stenotrophomonas, and Streptomyces formed the common core microbiome. Functional predictions of endophytic bacteria in halophytes highlighted multiple KEGG functional pathways, indicating recruitment of beneficial bacterial taxa to adapt to extreme hypersaline conditions, including plant growth-promoting, biocontrol, and halophilic bacteria.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12866-025-04309-5.

Halophilic microorganisms from extreme environments are increasingly recognized as promising sources of industrial enzymes and antimicrobial compounds. However, many saline ecosystems remain unexplored. In this study, the bacteriological profile of the extreme salt lake of Arzew (Oran, Algeria) was investigated for the first time. Twenty-nine halophilic bacterial strains were isolated from five saline soil samples around the lake and were preliminarily screened for the production of nine industrially relevant enzymes and antimicrobial activities. The enzymatic screening revealed that 69% of the isolates showed single or combined hydrolytic activities, with gelatinase, protease, inulinase, and lipase activities being the most prevalent. The antimicrobial screening showed significant activity against Gram-positive pathogens, Aspergillus niger, Fusarium sp., and Phytophthora infestans. Four of the most potent strains were selected for further phenotypic and molecular characterization. Based on 16S rRNA gene sequencing, the results showed that three isolates belonged to the genus Streptomyces and one representative isolate to the Nocardiopsis genus. Both phylotypes demonstrated tolerance to wide ranges of salt, pH, and temperature. Notably, isolate O61 displayed a distinct phylogenetic position, suggesting its potential affiliation as a novel Streptomyces species. These results provide a baseline microbial resource discovery from an underexplored Algerian hypersaline environment and highlight promising candidates for future detailed characterization for biotechnological applications.