Isolated Streptomyces Sp Research Articles

Taxonomic characterization and secondary metabolite production of newly isolated Streptomyces sp. MC12

An actinobacterium newly isolated from soil during a screening study was identified as Streptomyces sp. MC12 (GenBank accession number: PP757795) based on 16S rRNA analysis. For secondary metabolite production, fermentation was carried out in ISP 2 broth at 30°C, pH 7.3, for seven days under shaking conditions at 180 rpm. As a result of fermentation studies, the antagonistic effect of the crude extract, obtained through ethyl acetate extraction, against various microorganisms was determined. The MIC values of the extract against Staphylococcus aureus and Escherichia coli were 101.3 µg/mL and 153.6 µg/mL, respectively. It was also found to exhibit strong antifungal activity against Penicillium spp. Streptomyces sp. MC12, which displays both antifungal and antibacterial properties, is considered a potential secondary metabolite producer for future studies, particularly in pharmacology and the biocontrol of fungal pathogens.

Organophosphorus mineralizing-Streptomyces species underpins uranate immobilization and phosphorus availability in uranium tailings

Phosphate-solubilizing bacteria (PSB) are important but often overlooked regulators of uranium (U) cycling in soil. However, the impact of PSB on uranate fixation coupled with the decomposition of recalcitrant phosphorus (P) in mining land remains poorly understood. Here, we combined gene amplicon sequencing, metagenome and metatranscriptome sequencing analysis and strain isolation to explore the effects of PSB on the stabilization of uranate and P availability in U mining areas. We found that the content of available phosphorus (AP), carbonate-U and Fe-Mn-U oxides in tailings was significantly (P < 0.05) higher than their adjacent soils. Also, organic phosphate mineralizing (PhoD) bacteria (e.g., Streptomyces) and inorganic phosphate solubilizing (gcd) bacteria (e.g., Rhodococcus) were enriched in tailings and soils, but only organic phosphate mineralizing-bacteria substantially contributed to the AP. Notably, most genes involved in organophosphorus mineralization and uranate resistance were widely present in tailings rather than soil. Comparative genomics analyses supported that organophosphorus mineralizing-Streptomyces species could increase soil AP content and immobilize U(VI) through organophosphorus mineralization (e.g., PhoD, ugpBAEC) and U resistance related genes (e.g., petA). We further demonstrated that the isolated Streptomyces sp. PSBY1 could enhance the U(VI) immobilization mediated by the NADH-dependent ubiquinol-cytochrome c reductase (petA) through decomposing organophosphorous compounds. This study advances our understanding of the roles of PSB in regulating the fixation of uranate and P availability in U tailings.

Exploration of a multifunctional biocontrol agent Streptomyces sp. JCK-8055 for the management of apple fire blight.

Apple fire blight, caused by the bacterium Erwinia amylovora, is a devastating disease of apple and pear trees. Biological control methods have attracted much attention from researchers to manage plant diseases as they are eco-friendly and viable alternatives to synthetic pesticides. Herein, we isolated Streptomyces sp. JCK-8055 from the root of pepper and investigated its mechanisms of action against E. amylovora. Streptomyces sp. JCK-8055 produced aureothricin and thiolutin, which antagonistically affect E. amylovora. JCK-8055 and its two active metabolites have a broad-spectrum in vitro activity against various phytopathogenic bacteria and fungi. They also effectively suppressed tomato bacterial wilt and apple fire blight in in vivo experiments. Interestingly, JCK-8055 colonizes roots as a tomato seed coating and induces apple leaf shedding at the abscission zone, ultimately halting the growth of pathogenic bacteria. Additionally, JCK-8055 can produce the plant growth regulation hormone indole-3-acetic acid (IAA) and hydrolytic enzymes, including protease, gelatinase, and cellulase. JCK-8055 treatment also triggered the expression of salicylate (SA) and jasmonate (JA) signaling pathway marker genes, such as PR1, PR2, and PR3. Overall, our findings demonstrate that Streptomyces sp. JCK-8055 can control a wide range of plant diseases, particularly apple fire blight, through a combination of mechanisms such as antibiosis and induced resistance, highlighting its excellent potential as a biocontrol agent. KEY POINTS: • JCK-8055 produces the systemic antimicrobial metabolites, aureothricin, and thiolutin. • JCK-8055 treatment upregulates PR gene expression in apple plants against E. amylovora. • JCK-8055 controls plant diseases with antibiotics and induced resistance.

Isolation, Identification and Molecular Mechanism Analysis of the Nematicidal Compound Spectinabilin from Newly Isolated Streptomyces sp. DT10.

Plant parasitic nematodes (PPNs) are highly destructive and difficult to control, while conventional chemical nematicides are highly toxic and cause serious environmental pollution. Additionally, resistance to existing pesticides is becoming increasingly common. Biological control is the most promising method for the controlling of PPNs. Therefore, the screening of nematicidal microbial resources and the identification of natural products are of great significance and urgency for the environmentally friendly control of PPNs. In this study, the DT10 strain was isolated from wild moss samples and identified as Streptomyces sp. by morphological and molecular analysis. Using Caenorhabditis elegans as a model, the extract of DT10 was screened for nematicidal activity, which elicited 100% lethality. The active compound was isolated from the extracts of strain DT10 using silica gel column chromatography and semipreparative high-performance liquid chromatography (HPLC). The compound was identified as spectinabilin (chemical formula C28H31O6N) using liquid chromatography mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR). Spectinabilin exhibited a good nematicidal activity on C. elegans L1 worms, with a half-maximal inhibitory concentration (IC50) of 2.948 μg/mL at 24 h. The locomotive ability of C. elegans L4 worms was significantly reduced when treated with 40 μg/mL spectinabilin. Further analysis of spectinabilin against known nematicidal drug target genes in C. elegans showed that it acts via target(s) different from those of some currently used nematicidal drugs such as avermectin and phosphine thiazole. This is the first report on the nematicidal activity of spectinabilin on C. elegans and the southern root-knot nematode Meloidogyne incognita. These findings may pave the way for further research and application of spectinabilin as a potential biological nematicide.

Highly efficient shrimp shell recovery by solid-state fermentation with Streptomyces sp. SCUT-3

Owing to the rising global production of crustaceans, chitinous waste is being increasingly produced but poorly recycled. The development of new sustainable biorefinery methods is of urgent necessity for replacing traditional chemical recycling methods. A newly isolated Streptomyces sp. SCUT-3 strain, with robust protease secretion and chitin utilization abilities, was used for recycling shrimp shell waste (SSW) in this study. Under optimized conditions, 92.6 % of SSW protein was recovered by 5 d of solid-state fermentation (SSF), of which two-thirds was harvested as free amino acids (FAAs), and one-third as oligopeptides. The deproteinized SSW residue from SSF was easily subjected to calcium extraction, and 92.0 % of calcium was recovered in 30 min using lactic acid. The remaining residue was recovered as chitin products with high purity, a high acetylation rate of 90.5 %, and a low degree of crystallization. Altogether, the Streptomyces SSF-plus-lactic-acid method developed in this study can convert 100 g SSW into 33.6 g FAAs, 16.7 g oligopeptides, 7.4 g calcium (in the form of calcium lactate), and 19.5 g chitin. Analyses of the economic benefits and environmental impact revealed that this method has a low cost (20 %), high profit (10-fold), and a low environmental footprint (1.08 %) compared to traditional-chemical methods, and is superior to other newly developed physicochemical, enzymatic, and biofermentation methods. Higher protease production and constitutive chitinase expression SCUT-3 strains are under-constructed. The possibility of the enhanced super shell degradation strains to realize higher protein yields, synchronous protein, and chitin degradation, or sequential protein and chitin degradation for chitinous waste recycling is discussed. This green sustainable method developed in the study will light the way for the future shell waste recycling industry.

Antifungal Mechanism of Metabolites from Newly Isolated Streptomyces sp. Y1-14 against Banana Fusarium Wilt Disease Using Metabolomics.

Banana Fusarium wilt caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) is one of the most destructive banana diseases in the world, which limits the development of the banana industry. Compared with traditional physical and chemical practices, biological control becomes a promising safe and efficient strategy. In this study, strain Y1-14 with strong antagonistic activity against Foc TR4 was isolated from the rhizosphere soil of a banana plantation, where no disease symptom was detected for more than ten years. The strain was identified as Streptomyces according to the morphological, physiological, and biochemical characteristics and the phylogenetic tree of 16S rRNA. Streptomyces sp. Y1-14 also showed a broad-spectrum antifungal activity against the selected 12 plant pathogenic fungi. Its extracts inhibited the growth and spore germination of Foc TR4 by destroying the integrity of the cell membrane and the ultrastructure of mycelia. Twenty-three compounds were identified by gas chromatography-mass spectrometry (GC-MS). The antifungal mechanism was investigated further by metabolomic analysis. Strain Y1-14 extracts significantly affect the carbohydrate metabolism pathway of Foc TR4 by disrupting energy metabolism.

Production and characterization of α-amylase from indigenously isolated Streptomyces sp.

Streptomyces species have been exploited widely as microbial cell factories, especially for antibiotic production. However, their potential for alpha-amylase production has not been extensively studied. This study reports the isolation, molecular identification, and optimization of the physiological conditions for alpha-amylase production from Streptomyces sp., isolated from soil in Kotli Azad Kashmir. The maximum growth of Streptomyces MI-1 was observed at a neutral pH and a temperature of 35 °C. An amylase activity of 1.15 IU/mL was observed when 4% starch was added to the nutrient medium. During the submerged state fermentation, the maximum amylase activity of 2.136 IU/mL/min was observed after 144 h of incubation. The characterization of bacterial amylase revealed an optimum temperature of 40 °C, and its optimum pH was 7.0. Furthermore, during the study, examining the effect of different metal ions found that Mg2+ and Ca2+ ions had a positive effect, while Cu2+ and Fe2+ ions had an inhibitory effect compared to the control. This preliminary study provides basal line information for the discovery of novel microbes from the unexplored natural resources for amylase production, which will be used for many purposes.

Metabolomic Profiling and Molecular Networking of Nudibranch-Associated Streptomyces sp. SCSIO 001680

Antibiotic-resistant bacteria are the primary source of one of the growing public health problems that requires global attention, indicating an urgent need for new antibiotics. Marine ecosystems are characterized by high biodiversity and are considered one of the essential sources of bioactive chemical compounds. Bacterial associates of marine invertebrates are commonly a source of active medicinal and natural products and are important sources for drug discovery. Hence, marine invertebrate-associated microbiomes are a fruitful resource for excavating novel genes and bioactive compounds. In a previous study, we isolated Streptomyces sp. SCSIO 001680, coded as strain 63, from the Red Sea nudibranch Chromodoris quadricolor, which exhibited antimicrobial and antitumor activity. In addition, this isolate harbors several natural product biosynthetic gene clusters, suggesting it has the potential to produce bioactive natural products. The present study aimed to investigate the metabolic profile of the isolated Streptomyces sp. SCSIO 001680 (strain 63) and to predict their potential role in the host’s survival. The crude metabolic extracts of strain 63 cultivated in two different media were characterized by ultra-high-performance liquid chromatography and high-resolution mass spectrometry. The metabolomics approach provided us with characteristic chemical fingerprints of the cellular processes and the relative abundance of specific compounds. The Global Products Social Molecular Networking database was used to identify the metabolites. While 434 metabolites were detected in the extracts, only a few compounds were identified based on the standards and the public spectral libraries, including desferrioxamines, marineosin A, and bisucaberin, halichoblelide, alternarin A, pachastrelloside A, streptodepsipeptide P1 1B, didemnaketal F, and alexandrolide. This finding suggests that this strain harbors several novel compounds. In addition, the metabolism of the microbiome of marine invertebrates remains poorly represented. Thus, our data constitute a valuable complement to the study of metabolism in the host microbiome.

Potential Bioactive Compounds from Marine Streptomyces sp. and Their In Vitro Antibiofilm and Antibacterial Activities Against Antimicrobial-Resistant Clinical Pathogens.

Antimicrobial resistance issues have risen dramatically in recent years, posing a severe concern to humans worldwide. The urgent need to find novel compounds for pharmaceutical applications prompts the research of under-explored environments such as marine ecosystems. The present study was designed to discover novel secondary metabolites, and we have isolated about 30 actinomycetes from the marine soil samples collected in Thondi (Ramanathapuram, Tamil Nadu, India), where most isolates are associated with the genus Streptomyces. Out of 30, one potentially active strain (Streptomyces sp. SRMA3) was identified using primary and secondary screening methods against the drug-resistant clinical pathogens. The active metabolites extracted from the selected active isolate were subjected to partial purification and characterization using Fourier transform infrared spectrophotometer (FTIR) and gas chromatography-mass spectroscopy (GC-MS) analysis. The minimum inhibitory concentration (MIC) value was determined for the active metabolite. Further, the partially purified active fraction was revealed for its antibacterial and antibiofilm activity against drug-resistant clinical pathogens. Light and fluorescence microscopy detected the viability and adhesion of the biofilm-forming drug-resistant pathogens. Growth curve analysis showed that the active metabolite has the potential to inhibit drug-resistant pathogens. The synergistic effect of active metabolite with commercial antibiotics also revealed that it could enhance the activity of antibiotics in antimicrobial resistance pathogens. This study shows that the isolated Streptomyces sp. SRMA3 is a potentially active strain, and the metabolite derived from this strain has a good antibacterial and antibiofilm activity against antimicrobially resistant clinical pathogens and could be used for various biotechnological applications.

Biocontrol potential of a newly isolated Streptomyces sp. HSL-9B from mangrove forest on postharvest anthracnose of mango fruit caused by Colletotrichum gloeosporioides

Mango is an important tropical fruit in the world. Mango anthracnose is one of the most severe postharvest diseases caused by Colletotrichum gloeosporioides . Biocontrol by actinomycetes is considered as a promising strategy. Here, 67 actinomycetes were isolated from mangrove forest soils. A strain labelled with HSL-9B showed 63.21% of the inhibition ratio against C. gloeosporioides and broad-spectrum antifungal activities against the selected seven postharvest pathogens. The strain was assigned to Streptomyces malaysiensis based on the phenotypic, biochemical and whole-genomic profiles . Strain HSL-9B extracts significantly reduced the disease severity of mango anthracnose in vivo . 8 × EC 50 of extracts completely inhibited the infection of pathogen during the entire storage process. Total soluble sugar contents on harvested mangoes were effectively kept. 4 × EC 50 of extracts obviously inhibited spore germination and mycelial growth of C. gloeosporioides , resulting in mycelial rupture and cell ultrastructure destroying. The biosynthesis gene clusters (BGC) of secondary metabolites involved in antagonism were identified by compared with the whole-genome sequencing of strain HSL-9B. Fifteen compounds in strain HSL-9B extracts were obtained using the gas chromatography-mass spectrometry (GC-MS). 12-methyl-tridecanoic acid was one of dominant compounds identified in extracts. Hence, S. malaysiensis HSL-9B is an important bioresource for exploring novel natural products to manage postharvest disease. • Streptomyces strain with strong antifungal activities was isolated and identified. • Strain HSL-9B inhibited mango decay and maintained its quality during postharvest. • Extracts damaged the cell integrity and inhibited spore germination of pathogen. • Biosynthetic gene clusters were found in the sequencing genome of strain HSL-9B. • Several secondary metabolites were identified in strain HSL-9B extracts.

Biological Control of Fusarium oxysporum f. sp. cubense Tropical Race 4 in Banana Plantlets Using Newly Isolated Streptomyces sp. WHL7 from Marine Soft Coral.

Banana Fusarium wilt caused by Fusarium oxysporum f. sp. cubense is a disastrous fungal disease. Foc tropical race 4 (Foc TR4) infects almost all banana cultivars. Use of chemical fungicides caused serious environment pollution. Biological control with antagonistic microbes is a promising strategy for controlling Foc TR4. Here, strain WHL7 isolated from marine soft coral exhibited a high antifungal activity against Foc TR4. Based on the morphological and physicochemical profiles as well as the phylogenetic tree, the strain was assigned to Streptomyces sp. Fermentation broth of Streptomyces sp. WHL7 significantly increased the resistance of banana plantlets to Foc TR4 in the pot experiment. Analysis of antifungal mechanism showed that strain WHL7 extracts inhibited spore germination and mycelial growth of Foc TR4, and destroyed cell integrity and ultrastructure. Hence, Streptomyces sp. WHL7 is an important bioresource for exploring novel natural products and biofertilizer to manage Foc TR4.

Production of Cellulase by Soil Isolated Streptomyces sp.

Production of Cellulase by Soil Isolated Streptomyces sp.

Partial purification and application of β-mannanase for the preparation of low molecular weight galacto and glucomannan

The newly isolated Streptomyces sp. RDA1496 produced high activity of β-mannanase (415.96 IU/mL) when grown on optimized medium conditions. The produced enzyme was purified to partial homogeneity by ammonium sulphate precipitation followed by gel filtration. The β-mannanase was purified 5.12 fold to homogeneity with a specificity of 1118.79 IU/mg. The highly active fraction of β-mannanase from gel filtration, appeared as a protein band on SDS-PAGE gel with a molecular mass of 63.0 ± 2.0 kDa. β-mannanase was applied to prepare low molecular weight guar gum and konjac glucomannan by enzymatic de-polymerization. Gaur gum and konjac glucomannan (1.0% w/v) were hydrolyzed using the dialyzed β-mannanase, 3.0 mg/g of substrate for 24h. Molecular weight of hydrolyzed guar gum and konjac glucomannan were reduced to 40.73 kDa and 44.72 kDa. FTIR spectra of hydrolyzed mannan varied by different intensities of peaks compared to native mannan substrate and observed in vibrational area of O-H associated chemical group, –CH stretching of the –CH2 and –CH3 groups, and highly coupled C-C-O, C-OH and C-O-C of polymer backbone. Mannan substrates with lower molecular weight have great importance in nutrition and health industries, results indicate the hydrolyzed mannan substrates can be utilized as nutritional product for food industries.

Identification and phylogenetic differences of newly isolated Streptomyces sp.

Antimicrobial resistance and antibiotic use is a global health crisis today. Streptomyces is the source of most antimicrobials. Therefore, the similarities and differences within the species of Streptomyces are of great importance. In this study, isolation and identification of 3 different Streptomyces species isolated from sediment from the Dicle region were performed. Then, 16S rRNA gene sequence was obtained and the similarities and differences between species were revealed. As a result of the study, bacteria contained clorometric differences, when looking at the spore chain morphology in the SEM image, a knobby structure was formed, 16S rRNA sequences longer than 1000bp and in the phylogenetic tree created, 1 isolate was closely similar to the sequences obtained from GenBank (93

Production of Protease on Wheat Bran by a Newly Isolated Streptomyces SP. Under Solid State Fermentation

Proteases are a group of enzymes that catalyse the degradation of proteins resulting in the production of their amino acid constituents. In the present study newly isolated Streptomyces sp. was subjected to produce proteases through solid state fermentation while wheat bran was used as substrate. To produce proteases, a local strain Streptomyces sp. was isolated from a soil sample of Ezzemouls saltpan, located in Ain M'lila (East of Algeria). The phenotypic and phylogenetic studies of this strain showed that it represents probably a new species. The SSF production medium for Streptomyces sp. was optimized using Plackett and Burman statistical methods. The results showed a maximum activity on basal wheat bran medium supplemented with 1% fructose. The best SSF humidifying solution was pH 9.0 phosphate buffer at 50% moisture. Protease has an optimum at pH 7.0, which is a typical characteristic of neutral proteases. The optimum temperature was 60°C and proved stable up to 80°C. The results showed that the novel Streptomyces sp. isolate is a good producer of extracellular neutral protease on wheat bran, which can be beneficial for industries. J. Bio-Sci. 29(1): 33-48, 2021 (June)

The Isolation of a Novel Streptomyces sp. CJ13 from a Traditional Irish Folk Medicine Alkaline Grassland Soil that Inhibits Multiresistant Pathogens and Yeasts

The World Health Organization recently stated that new sources of antibiotics are urgently required to stem the global spread of antibiotic resistance, especially in multiresistant Gram-negative bacteria. Although it was thought that many of the original sources of antibiotics were exhausted, innovative research has revealed promising new sources of antibiotic discovery in traditional medicine associated with Streptomyces. In this work we investigated the potential of a specific limestone grassland soil, associated with Irish folk medicine, as a new source of antimicrobial discovery. Using selective enrichment and isolation techniques on a limestone grassland soil sample obtained from Boho, West Fermanagh, we isolated Streptomyces sp. CJ13. This bacterium inhibited the growth of a broad range of pathogens in vitro including Gram positive Staphylococcus aureus (MRSA 43300) and Gram negative multiresistant Pseudomonas aeruginosa (PA01), as well as the anaerobic bacteria Propionibacterium acnes and the yeast Starmerella bombicola. Genome sequencing and phylogenetic analysis revealed Streptomyces sp. CJ13 to be closely related to an unclassified Streptomyces sp. MJM1172, Streptomyces sp. Mg1 and two species known as Streptomyces sp. ICC1 and ICC4 from a karst region in British Columbia. The closest type species to Streptomyces sp. CJ13 was Streptomyces lavendulae subspecies lavendulae. Analysis of Streptomyces sp. CJ13 whole genome sequence using the secondary metabolite prediction tool antiSMASH revealed similarities to several antibiotic gene synthesis clusters including salinichelin, mediomycin A, weishanmycin, combamide, heat stable antifungal factor and SAL-2242. These results demonstrate the potential of this alkaline grassland soil as a new resource for the discovery of a broad range of antimicrobial compounds including those effective against multiresistant Gram negative bacteria.

Newly Isolated Streptomyces sp. JBS5-6 as a Potential Biocontrol Agent to Control Banana Fusarium Wilt: Genome Sequencing and Secondary Metabolite Cluster Profiles.

Banana is a key staple food and fruit in countries all over the world. However, the development of the global banana industry is seriously threatened by Fusarium wilt disease, which is caused by Fusarium oxysporum f. sp. cubense (Foc). In particular, Foc tropical race 4 (Foc TR4) could infect more than 80% of global banana and plantain crops. Until now, there were no commercial chemicals or resistant cultivars available to control the disease. Biological control using actinomycetes is considered a promising strategy. In this study, 88 actinomycetes were isolated from a banana orchard without symptoms of Fusarium wilt disease for more than 10 years. An actinobacterial strain labeled as JBS5-6 has exhibited strong antifungal activities against Foc TR4 and other selected 10 phytopathogenic fungi. Based on phenotypic and biochemical traits as well as complete genome analysis, strain JBS5-6 was assigned to Streptomyces violaceusniger. Extracts of the strain inhibited the mycelial growth and spore germination of Foc TR4 by destroying membrane integrity and the ultrastructure of cells. The complete genome of strain JBS5-6 was sequenced and revealed a number of key function gene clusters that contribute to the biosynthesis of active secondary metabolites. Sixteen chemical compounds were further identified by gas chromatography-mass spectrometry (GC-MS). 5-hydroxymethyl-2-furancarboxaldehyde was one of the dominant components in strain JBS5-6 extracts. Moreover, fermentation broth of strain JBS5-6 significantly reduced the disease index of banana seedlings by inhibiting the infection of Foc TR4 in a pot experiment. Hence, strain JBS5-6 is a potential biocontrol agent for the management of disease and the exploitation of biofertilizer.

A Newly Isolated Streptomyces sp. YYS-7 With a Broad-Spectrum Antifungal Activity Improves the Banana Plant Resistance to Fusarium oxysporum f. sp. cubense Tropical Race 4.

Fusarium wilt of banana caused by Fusarium oxysporum f. sp. cubense (Foc) is one of the most destructive diseases, severely limiting the development of banana industry. Especially, Foc tropical race 4 (Foc TR4) can infect and destroy almost all banana cultivars. Until now, there is still a lack of an effective method for controlling fusarium wilt. A biocontrol strategy using Actinobacteria is considered as a promising method for management of disease and pest. In this study, 229 Actinobacteria were isolated from rhizosphere soil samples of a primitive ecological mountain. An actinobacterium strain marked with YYS-7 exhibited a high antifungal activity against Foc TR4. Combining the physiological and biochemical characteristics as well as alignment of the 16S rRNA sequence, the strain YYS-7 was assigned to Streptomyces sp. The crude extracts of Streptomyces sp. YYS-7 obviously inhibited the mycelial growth of Foc TR4. The cell integrity and ultrastructure were seriously destroyed. In addition, Streptomyces sp. YYS-7 and crude extracts also showed a broad-spectrum antifungal activity against the selected seven phytopathogenic fungi. A gas chromatography-mass spectrometry (GC-MS) was used to predict the antifungal metabolites. A total of eleven different compounds were identified, including phenolic compounds, hydrocarbons, esters and acids. In the pot experiment, the crude extracts can significantly improve the banana plant’s resistance to Foc TR4. Hence, Streptomyces sp. YYS-7 will be a potential biocontrol agent for the biofertilizer exploitation and the discovery of new bioactive substances.

Antimicrobial Activity of Microorganisms Isolated from Ant Nests of Lasius niger.

In this study, the microbial communities of two nests of black garden ants (Lasius niger) in the hollows of stem branches of old apple trees were found to have similar species compositions: each community contained representatives of three species from the Bacillaceae family and one species of actinomycetes from the genus Streptomyces. In total, four types of bacilli and two actinomycetes were isolated. Actinomycetes were identified as Streptomyces antibioticus-like and Streptomyces sp. None of the bacilli had antibiotic activity, whereas both streptomycetes produced antibiotics that inhibited the growth of Gram-positive bacteria in vitro, including isolates from their community. Antibiotic compounds of S. antibioticus-like strain INA 01148 (Institute of New Antibiotics) were identified as actinomycin D and its closest homologue, actinomycin A. Actinomycins presumably change the microbial community of the ant nest substrate as they act against Gram-positive bacteria and against fungi and Gram-negative bacteria. The antibiotic activity of the isolated Streptomyces sp. INA 01156 is of interest, since the substances produced by this strain inhibit the growth of drug-resistant bacteria, including methicillin-resistant Staphylococcus aureus INA 00761 (MRSA) and vancomycin-resistant strain Leuconostoc mesenteroides VKPM B-4177 (VR) (VKPM–National Collection of Industrial Microorganisms (Russian acronym)).

Streptomyces sp. VN1, a producer of diverse metabolites including non-natural furan-type anticancer compound

Streptomyces sp. VN1 was isolated from the coastal region of Phu Yen Province (central Viet Nam). Morphological, physiological, and whole genome phylogenetic analyses suggested that strain Streptomyces sp. VN1 belonged to genus Streptomyces. Whole genome sequencing analysis showed its genome was 8,341,703 base pairs in length with GC content of 72.5%. Diverse metabolites, including cinnamamide, spirotetronate antibiotic lobophorin A, diketopiperazines cyclo-L-proline-L-tyrosine, and a unique furan-type compound were isolated from Streptomyces sp. VN1. Structures of these compounds were studied by HR-Q-TOF ESI/MS/MS and 2D NMR analyses. Bioassay-guided purification yielded a furan-type compound which exhibited in vitro anticancer activity against AGS, HCT116, A375M, U87MG, and A549 cell lines with IC50 values of 40.5, 123.7, 84.67, 50, and 58.64 µM, respectively. In silico genome analysis of the isolated Streptomyces sp. VN1 contained 34 gene clusters responsible for the biosynthesis of known and/or novel secondary metabolites, including different types of terpene, T1PKS, T2PKS, T3PKS, NRPS, and hybrid PKS-NRPS. Genome mining with HR-Q-TOF ESI/MS/MS analysis of the crude extract confirmed the biosynthesis of lobophorin analogs. This study indicates that Streptomyces sp. VN1 is a promising strain for biosynthesis of novel natural products.