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This study aims to determine how ZnO nanoparticles affect rice straw during solid-state fermentation and cellulase production. The zinc oxide (ZnO) nanoparticles of concentration 1 mg/gm was supplemented in a solid-state fermentation medium with the isolated actinobacterial species Streptomycetes calvus for cellulase production. It was also noticed that the addition of the nanoparticles catalyzed the biodegradation of rice straw complex structure and facilitates cellulase production. So, higher cellulase activities were observed in the enzymes produced in the presence of the ZnO, i.e., 0.38 IU/ml, followed by 0.27 IU/ml in control (without nanoparticles). Further, XRD, SEM and FTIR clearly showed the degradation of lignocellulose and morphological changes in rice straw structure during fermentation. Additionally, higher FPases activities and saccharification percentage indicated that nanoparticle-mediated cellulases would be a better option for further applications. [ABSTRACT FROM AUTHOR]

Introduction: Pyrrhoderma noxium is a plant pathogen that causes economic losses in agricultural and forestry industries, including significant destruction to amenity trees within the city of Brisbane in Australia. Use of chemical control agents are restricted in public areas, there is therefore an urgent need to investigate biological control approaches. Members of the phylum Actinomycetota, commonly known as actinomycetes, are known for their industrially important secondary metabolites including antifungal agents. They have proven to be ideal candidates to produce environmentally friendly compounds including the volatile organic compounds (VOCs) which can be used as biofumigants. Methods: Different Streptomyces species (n=15) previously isolated from the guts of termites and stored in the University of the Sunshine Coast’sMicrobial Library were tested for their antifungal VOCs against Pyrrhoderma noxium. Results: Fourteen of them were found to display inhibition (39.39-100%) to the mycelial development of the pathogen. Strongest antifungal activity displaying isolates USC-592, USC-595, USC-6910 and USC-6928 against the pathogen were selected for further investigations. Their VOCs were also found to have plant growth promotional activity observed for Arabidopsis thaliana with an increase of root length (22-36%) and shoot length (26-57%). The chlorophyll content of the test plant had a slight increase of 11.8% as well. Identified VOCs included geosmin, 2-methylisoborneol, 2-methylbutyrate, methylene cyclopentane, β-pinene, dimethyl disulfide, ethyl isovalerate, methoxyphenyloxime and α-pinene. Additionally, all 15 Streptomyces isolates were found to produce siderophores and indole acetic acid as well as the enzyme chitinase which is known to break down the fungal cell wall. Discussion: Findings indicate that termite gut-associated streptomycetes might be used to control Pyrrhoderma noxium by utilizing their wide range of inhibitory mechanisms. [ABSTRACT FROM AUTHOR]

One-hundred-and-fifty strains of streptomycetes have been isolated from gray and dark gray forest soils, as well as from typical chernozem. The isolated strains were analyzed in vitro for antimicrobial activity on nutrient media and in gray forest soil against 23 collection pathogenic test cultures of fungi and bacteria. Four biologically active isolates with a wide action spectrum have been identified and deposited at the All-Russia Collection of Industrial Microorganisms of the National Research Center "Kurchatov Institute" under the following numbers: Streptomyces xiamenensis TB VKPM As-2204, Streptomyces anulatus TG VKPM As-2203, Streptomyces sindenensis TK VKPM As-2205, and Streptomyces flavovirens TT VKPM As-2202. A study of the effect of presowing treatment of wheat seeds with 15-day culture liquids of S. xiamenensis TB VKPM As-2204, S. anulatus TG VKPM As-2203, and S. sindenensis TK VKPM As-2205 for germination rates and levels of infection with F. graminearum has revealed that they inhibited the growth of a pathogenic fungus and improved the seed vigor and germination of wheat. The resulting strains of soil actinomycetes can be used in biotechnology for creating new bioinoculants to combat phytopathogenic bacteria and fungi. The strains can also be used for stimulating the plant growth, as well as for soil bioremediation in organic farming. Based on the HPLC method (high-performance liquid chromatography), we have identified specialized antimicrobial metabolites of monosporous strain suspensions. The identified antibiotics are N-Butylbenzenesulfonamide, 1-(1H-Benzo[d]imidazol-2-yl)ethan-1-ol, 2-[(3S)-1-(Cyclohexylmethyl)-3-pyrrolidinyl]-1H-benzimidazole-5-carbonitrile, Cyclo(leucylprolyl), and Cyclo(phenylalanyl-prolyl). The identified antiseptics are Cetrimonium and Carvone. The identified phytohormone is auxin indole-3-acetic acid (IAA). Observation of the dynamics of development of the introduced actinobacteria in soil samples has shown a high activity of streptomycetes that use chitin. Analysis of the diversity of the prokaryotic complex of the studied soil samples based on high-throughput sequencing of the conserved region of the 16S rRNA gene has revealed its controlling role in the microbial community during the introduction of S. xiamenensis TB VKPM As-2204, which is determined by its antibiotic-forming activity. [ABSTRACT FROM AUTHOR]

Plant fungal pathogen Pyrrhoderma noxium is responsible for the destructive and invasive disease of brown root rot currently affecting the city of Brisbane, Australia. In order to address this issue, environmentally friendly and safe alternatives to chemical control are preferred due to the city's public setting. Antifungal natural products are ideal candidates as biological control alternatives and can be detected through investigating the metabolomes of microbial symbionts. Within this study, an NMR-based metabolomics approach was applied to fermentation extracts obtained from 15 termite gut-associated streptomycetes. By analysing the NMR spectra, six of the extracts which displayed similar chemical profiles exhibited antifungal activity against the P. noxium pathogen. The major compound within these extracts was identified as acetomycin using NMR and X-ray crystallography analyses. This is the first reporting of acetomycin as a potential natural product fungicide, particularly as an antifungal agent against P. noxium. Inhibitory activity was also found against other important fungal crop pathogens, including Aspergillus niger, Botrytis cinerea, and Alteranaria alternata. Further experimentation using a woodblock test found inhibitory activity on the growth of the P. noxium pathogen for up to 3 weeks and a significant difference in the integrity of the woodblocks when conducting compression strength tests after 6 weeks. Therefore, acetomycin may be used as a biological control agent and natural product fungicide against P. noxium. [ABSTRACT FROM AUTHOR]

Worldwide mounting demand for better food production to nurture exasperating population emphasizes on reduced crop losses. The incidence of pathogens into the agricultural fields has tend to dwindle plethora of cereal, vegetable, and other fodder crops. This, in turn, has seriously impacted the economic losses on global scale. Apart from this, it is quite challenging to feed the posterity in the coming decades. To counteract this problem, various agrochemicals have been commercialized in the market that no doubt shows positive results but along with adversely affecting the ecosystem. Therefore, the excessive ill‐fated use of agrochemicals to combat the plant pests and diseases highlights that alternatives to chemical pesticides are need of the hour. In recent days, management of plant diseases using plant‐beneficial microbes is gaining interest as safer and potent alternatives to replace chemically based pesticides. Among these beneficial microbes, actinobacteria especially streptomycetes play considerable role in combating plant diseases along with promoting the plant growth and development along with their productivity and yield. The mechanisms exhibited by actinobacteria include antibiosis (antimicrobial compounds and hydrolytic enzymes), mycoparasitism, nutrient competition, and induction of resistance in plants. Thus, in cognizance with potential of actinobacteria as potent biocontrol agents, this review summarizes role of actinobacteria and the multifarious mechanisms exhibited by actinobacteria for commercial applications. [ABSTRACT FROM AUTHOR]

IntroductionPyrrhoderma noxium is a plant pathogen that causes economic losses in agricultural and forestry industries, including significant destruction to amenity trees within the city of Brisbane in Australia. Use of chemical control agents are restricted in public areas, there is therefore an urgent need to investigate biological control approaches. Members of the phylum Actinomycetota, commonly known as actinomycetes, are known for their industrially important secondary metabolites including antifungal agents. They have proven to be ideal candidates to produce environmentally friendly compounds including the volatile organic compounds (VOCs) which can be used as biofumigants.MethodsDifferent Streptomyces species (n=15) previously isolated from the guts of termites and stored in the University of the Sunshine Coast’sMicrobial Library were tested for their antifungal VOCs against Pyrrhoderma noxium.ResultsFourteen of them were found to display inhibition (39.39-100%) to the mycelial development of the pathogen. Strongest antifungal activity displaying isolates USC-592, USC-595, USC-6910 and USC-6928 against the pathogen were selected for further investigations. Their VOCs were also found to have plant growth promotional activity observed for Arabidopsis thaliana with an increase of root length (22-36%) and shoot length (26-57%). The chlorophyll content of the test plant had a slight increase of 11.8% as well. Identified VOCs included geosmin, 2-methylisoborneol, 2-methylbutyrate, methylene cyclopentane, β-pinene, dimethyl disulfide, ethyl isovalerate, methoxyphenyl-oxime and α-pinene. Additionally, all 15 Streptomyces isolates were found to produce siderophores and indole acetic acid as well as the enzyme chitinase which is known to break down the fungal cell wall.DiscussionFindings indicate that termite gut-associated streptomycetes might be used to control Pyrrhoderma noxium by utilizing their wide range of inhibitory mechanisms.

Background. Streptomycetes were and remain a source of new antimicrobial compounds of various nature. A new wave of interest in such research is associated with the possibilities of applied genomics to reveal the hidden biosynthetic potential of streptomycetes, and therefore the discovery of new practically valuable antimicrobial products. The problem of antibiotic resistance of pathogens can be solved by creating compositions of active substances of different nature to overcome the protective mechanisms of pathogens. Objective. The purpose of the work was to establish and evaluate the antimicrobial and cytotoxic characteristics of the new antibiotic streptofungin, synthesized by Streptomyces albus 2435 (CMIM-S-668) and its mutant strains 2435/М, UN44, 4S, US101, AE6, 105, 80/5. Methods. To establish the characteristics of streptofungin, the antagonistic activity of selected S. albus producer strains was determined (by the radial streak method), the minimum inhibitory concentration of the antibiotic (by the serial dilution method), and cytotoxicity was determined by the MTT test with resazurin. Results. The activity of the antibiotic streptofungin against Candida fungi (C. albicans, C. utilis) is shown. Minimum inhibitory concentrations of streptofungin were determined for C. albicans ATCC 10231 (10 μg/ml), B. subtilis ATCC 6633 (200 μg/ml) and P. aeruginosa ATCC 9027 (500 μg/ml). According to the resazurin test, streptofungin does not show a cytotoxic effect in a wide range of concentrations from 2.5 to 500 μg/ml, and therefore can be considered potentially permissible for humans and animals in the studied concentrations. Conclusions. The antagonistic activity of mutant strains of S. albus culture is due to the action of a complex of antimicrobial products that have a different antimicrobial spectrum and mechanism of action. The obtained results give reasons to consider streptofungin as a promising pharmaceutical substance with antifungal action, as well as to consider the possibility of its combination with the bacteriolytic enzyme complex of the same culture for the development of an antimicrobial agent with a wide spectrum of action.

The antibiotic lincomycin binds to the 23S ribosomal RNA peptidyl transferase loop region to inhibit protein synthesis. However, lincomycin can also stimulate the growth and secondary metabolism of actinomycetes in a concentrationdependent manner. In Streptomyces coelicolor A3(2), lincomycin stimulates the production of the blue-pigmented antibiotic actinorhodin at concentrations below the minimum inhibitory concentration. To better understand the molecular mechanism underlying these concentration-dependent positive effects, this study investigated how the target molecule, the ribosome, undergoes dynamic changes in the presence of lincomycin and explored the ribosome-related factors involved. Lincomycin, at a concentration that stimulates actinorhodin production of S. coelicolor A3(2), could restore temporarily arrested ribosome function by utilizing ribosome-related proteins and translation factors, presumably under the control of the transcription factor WblC protein that confers intrinsic resistance to multiple translation-inhibiting antibiotics, to eventually produce stable and active ribosomes even during the late growth phase. This qualitatively and quantitatively positive ribosome alteration can be advantageous for producing actinorhodin biosynthetic enzymes. A series of gene expression and biochemical analyses revealed that lincomycin at the concentration that induces ribosomal stabilization in S. coelicolor A3(2) could influence the localization of the 20S proteasome-related proteins, resulting in reduced proteasome activity. These findings suggest that the functional analysis of 20S proteasome represents a potential pivotal challenge for understanding the molecular mechanism of ribosome stabilization induced by lincomycin. Therefore, as lincomycin can dynamically alter its target molecule, the ribosome, we discuss the future issues and prospects for an increased understanding of the concentration-dependent properties of antibiotics. [ABSTRACT FROM AUTHOR]

Pyrrhoderma noxium is a plant fungal pathogen that induces the disease of brown root rot in a large variety of tree species. It is currently infecting many of the amenity trees within Brisbane City of Queensland, Australia. Steering away from harmful chemical fungicides, biological control agents offer environmentally friendly alternatives. Streptomycetes are known for their production of novel bioactive secondary metabolites with biocontrol potential, particularly, streptomycete symbionts isolated from unique ecological niches. In this study, 37 termite gut-associated actinomycete isolates were identified using molecular methods and screened against P. noxium. A majority of the isolates belonged to the genus Streptomyces, and 15 isolates exhibited strong antifungal activity with up to 98.5% mycelial inhibition of the fungal pathogen. MS/MS molecular networking analysis of the isolates' fermentation extracts revealed several chemical classes with polyketides being among the most abundant. Most of the metabolites, however, did not have matches to the GNPS database, indicating potential novel antifungal compounds in the active extracts obtained from the isolates. Pathway enrichment and overrepresentation analyses revealed pathways relating to polyketide antibiotic production, among other antibiotic pathways, further confirming the biosynthetic potential of the termite gut-associated streptomycetes with biocontrol potential against P. noxium. [ABSTRACT FROM AUTHOR]

Strain K-11 was isolated from the highly saline brown semi-desert soil of the Astrakhan region. Based on analysis of the 16S rRNA gene sequence, this strain was identified as Streptomyces carpaticus K-11 RCAM04697 (SCPM-O-B-9993). Whole genome sequencing of the strain was performed. Phytotoxicity, antiviral, antioxidant, antifungal, and insecticidal activities of the strain were studied. All extracts and suspensions of S. carpaticus strain RCAM04697 had plant-stimulating activity. Antiviral properties was exhibited as suppression of development and propagation of viral pathogens in laboratory conditions: Tomato mosaic virus (ToMV)—26.3%, Cucumber mosaic virus (CMV)—33.8%, Y-Potato virus (Potato Y potyvirus, PVY)—51.3%, Potato X-virus (PVX) (Potato X potyvirus, PVX)—41.3%. The highest antioxidant activity was shown by a suspension of S. carpaticus strain RCAM04697 (88.8%) and its aqueous-alcoholic (20 : 80) extract (76.0%). The strain inhibited growth of the phytopathogenic fungus Fusarium sporotrichioides to varying degrees. The insecticidal activity against Aphis fabae after 6 h of treatment was 100% in the variants with suspension treatment, water-alcohol (80 : 20, 50 : 50), methanol, and hexane extracts. The metabolites of the S. carpaticus RCAM04697 strain included flavonoids, alkaloids, glycosides, organic acids (isocitric, acetic, fumaric, lactic, pyruvic, and malic), alcohols, aldehydes, hydrocarbons, ethers, sulfur-containing compounds, and other groups of low-molecular weight organic compounds. [ABSTRACT FROM AUTHOR]

MetNase might be a valuable source for different medical applications. MetNase has the potential to be used against a wide range of tumour cell types as an anticancer agent. The purpose of this research is to screen and develop optimal conditions of streptomycetes isolates for MetNase production. For this study, 34 randomly selected streptomyces isolates from soil and marine water were used. The isolates that can produce MetNase were qualitatively selected using a quick plate assay method. When the pH was set to 7.0, the incubation temperature was set to 30 °C, and the carbon and nitrogen sources were glucose and peptone, respectively, the highest levels of MetNase synthesis were attained. [ABSTRACT FROM AUTHOR]

The aim of the work is to identify strains of Streptomyces's in the genomes of which there are nucleotide sequences similar to the gene cluster determining the synthesis of landomycin A (lan-cluster) and establish the level of similarity of their primary structures and organizations. Methods. Information on the sequences of the lackluster of Streptomyces cyanogen's S136 and chromosomal DNAs of S. cyanogen's S136, Streptomyces laculatispora NRRL B-24909, and Streptomyces griseoluteus JCM 4765 and their annotations are presented in the GenBank database on the NSBI server. A computerized analysis of the nucleotide sequences of Streptomyces's was done using the program BLASTN from the server NSBI. Results. Th e localization of the lan-cluster in the terminal region of the S.cyanogenus S136 genome has been shown. Th e nucleotide sequences similar to the lan-cluster sequence of S. cyanogen's S136 were found in the genomes of two strains (S. laculatispora NRRL B-24909 and S. griseoluteus JCM 4765). Streptomyces's (S. cyanogenus S136, S. laculatispora NRRL B-24909, and S. griseoluteus JCM 4765) are not genetically related strains. Conclusions. Th ere are newly found probable lan-clusters in the genomes of two Streptomyces's strains (S. laculatispora NRRL B-24909 and S. griseoluteus JCM 4765). Landomycin clusters of three strains are organized according to the same scheme. Th e clusters of lagenas are present in the genomes of genetically unrelated Streptomyces's. [ABSTRACT FROM AUTHOR]

Forty streptomycetes were isolated from the soils of farms in Riyadh. Only three isolates (St-2, St-9, and St-25) exhibited cellulolytic-ligninolytic activity, with the St-9 isolate exhibiting the highest activity and identified as Streptomyces lazureus. The optimum environmental and nutritional conditions for maximum cellulolytic-ligninolytic activity were determined as fermentation batch of pH of 7.5, inoculum size of 200 µL of bacterial suspension, incubation period of 7 d, and incubation temperature of 30°C. In addition, the fermentation batch contained peptone and yeast extract as the best nitrogen and carbon sources, respectively. Cellulase and ligninase were purified via gel filtration column chromatography. The accumulated end-product of the fermentation process was glucose powder, which was subjected to a partial characterization process. The glucose powder appeared white, melted at 146°C, was highly soluble in water, slightly soluble in ethanol, and insoluble in ethyl ether. The glucose solution appeared clear without precipitates and had a low electric conductivity of 15 µS.cm-1.

The paper determines the number and structure of actinomycete complexes associated with the roots of the medicinal plant – leuzea safflower (Rhaponticum carthamoides (Willd.) Iljin) during long-term cultivation on sod-podzolic soil. The total number of actinomycetes in the rhizosphere varied within (4.4-13.2)×105 CFU/g of soil, and in the rhizoplane ‒ within (7.6-24.1)×103 CFU/g of roots. The complex of mycelial prokaryotes is represented by the genera Streptomyces, Micromonospora, Streptosporangium, Streptoverticillium and oligospore forms. Streptomycetes dominated both in the rhizosphere and in the rhizoplane of leuzea safflower. From these microlocuses, 30 cultures of mycelial prokaryotes were isolated using selective techniques. The cultural-morphological and physiological-biochemical properties of the isolates were studied. High-performance screening conducted using a dual reporter system revealed among 19 isolates associated with leuzea roots the ability to produce protein synthesis inhibitors in four (21 %) streptomycetes cultures. PCR detection of type II polyketide synthetase genes did not reveal their carriers among streptomycetes associated with leuzea. A significant proportion (67 %) of streptomycetes isolates from the rhizosphere and rhizoplana of leuzea had moderate and high cellulase activity. It has been established that the majority (92 %) of streptomycetes in the rhizoplana complex produce indole compounds (IUC) in the amount of 40±16.1 mcl/ml, up to 61 % of isolates produce water-soluble metabolites of antifungal action. New strains of streptomyces antagonists of phytopathogenic fungi, cellulolytics and auxin producers promising for further study have been identified.

Actinomycetes produce secondary metabolites with many bioactivities such as antimicrobial, which can be useful as alternatives against resistant bacterial strains. Therefore, the screening of new habitats is likely to provide new strains with high potential. In this work, the antimicrobial capacity was used to select Streptomyces sp. strains isolated from Raf Raf forest (Tunisia). From the strain displaying higher activity, FR7, an ethyl acetate extract was prepared under optimized culturing conditions (10 days at 30°C in ISP2 medium with initial pH 8), showing significant antimicrobial activity against Micrococcus luteus and Staphylococcus aureus (MIC = 5 μg ml−1), and Listeria monocytogenes and Pseudomonas aeruginosa (MIC = 20 μg ml−1). The extract displayed strong DPPH radical scavenging activity (IC 50 = 1.3 μg ml−1) and protection of yeast cells from H2O2-induced oxidative stress determined by flow cytometry with dichlorofluorescein diacetate. The crude extract showed the presence of polyketides, with methylsalicylic acid as moiety, a large and diverse group of secondary metabolites with a wide range of bioactivities, including antioxidant and antibacterial. Based on 16S RNA gene sequences, strain FR7 was identified as belonging to genus Streptomyces with high resemblance to S. iakyrus. Streptomyces sp. FR7 has great potential as a source of antibacterial and antioxidant metabolites. [ABSTRACT FROM AUTHOR]

The use of chemical fertilizers and pesticides has caused harmful impacts on the environment with the increase in economic burden. Biofertilizers are biological products containing living microorganisms capable of improving plant growth through eco-friendly mechanisms. In this work, three actinobacterial strains Streptomyces violaceoruber, Streptomyces coelicolor, and Kocuria rhizophila were characterized for multiple plant growth promoting (PGP) traits such as indole acetic acid production, phosphate solubilization, N2-fixation, and drought and salt tolerance. Then, these strains were investigated for their secreted and cellular metabolome, revealing a rich arsenal of bioactive molecules, including antibiotics and siderophores, with S. violaceoruber being the most prolific strain. Furthermore, the in vivo assays, performed on tomato (Solanum lycopersicum L.), resulted in an improved germination index and the growth of seedlings from seeds treated with PGP actinobacteria, with a particular focus on S. violaceoruber cultures. In particular, this last strain, producing volatile organic compounds having antimicrobial activity, was able to modulate volatilome and exert control on the global DNA methylation of tomato seedlings. Thus, these results, confirming the efficacy of the selected actinobacteria strains in promoting plant growth and development by producing volatile and non-volatile bioactive molecules, can promote eco-friendly alternatives in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Plant fungal pathogen Pyrrhoderma noxium is responsible for the destructive and invasive disease of brown root rot currently affecting the city of Brisbane, Australia. In order to address this issue, environmentally friendly and safe alternatives to chemical control are preferred due to the city’s public setting. Antifungal natural products are ideal candidates as biological control alternatives and can be detected through investigating the metabolomes of microbial symbionts. Within this study, an NMR-based metabolomics approach was applied to fermentation extracts obtained from 15 termite gut-associated streptomycetes. By analysing the NMR spectra, six of the extracts which displayed similar chemical profiles exhibited antifungal activity against the P. noxium pathogen. The major compound within these extracts was identified as acetomycin using NMR and X-ray crystallography analyses. This is the first reporting of acetomycin as a potential natural product fungicide, particularly as an antifungal agent against P. noxium. Inhibitory activity was also found against other important fungal crop pathogens, including Aspergillus niger, Botrytis cinerea, and Alteranaria alternata. Further experimentation using a woodblock test found inhibitory activity on the growth of the P. noxium pathogen for up to 3 weeks and a significant difference in the integrity of the woodblocks when conducting compression strength tests after 6 weeks. Therefore, acetomycin may be used as a biological control agent and natural product fungicide against P. noxium.

There is a real consensus that new antibiotics are urgently needed and are the best chance for combating antibiotic resistance. The phylum Actinobacteria is one of the main producers of new antibiotics, with a recent paradigm shift whereby rare actinomycetes have been increasingly targeted as a source of new secondary metabolites for the discovery of new antibiotics. However, this review shows that the genus Streptomyces is still the largest current producer of new and innovative secondary metabolites. Between January 2015 and December 2020, a significantly high number of novel Streptomyces spp. have been isolated from different environments, including extreme environments, symbionts, terrestrial soils, sediments and also from marine environments, mainly from marine invertebrates and marine sediments. This review highlights 135 new species of Streptomyces during this 6-year period with 108 new species of Streptomyces from the terrestrial environment and 27 new species from marine sources. A brief summary of the different pre-treatment methods used for the successful isolation of some of the new species of Streptomyces is also discussed, as well as the biological activities of the isolated secondary metabolites. A total of 279 new secondary metabolites have been recorded from 121 species of Streptomyces which exhibit diverse biological activity. The greatest number of new secondary metabolites originated from the terrestrial-sourced Streptomyces spp.

The Brown root rot pathogen Pyrrhoderma noxium (Corner) L.W. Zhou and Y.C. Dai is known to infect a large number of culturally and economically important plant species across the world. Although chemical control measures have been effective in managing this pathogen, their adverse effects on the ecosystem have limited their use. The use of biological control agents (BCAs) thus is generally accepted as an environmentally friendly way of managing various pathogens. Testing various consortia of the BCAs with different antagonistic mechanisms may even provide better disease protection than the use of a single BCA against aggressive plant pathogens such as the P. noxium. In the presented study, the wood decay experiment and the pot trial confirmed that the consortium of Trichoderma strains (#5029 and 5001) and streptomycetes (#USC−6914 and #USC−595-B) used was effective in protecting wood decay and plant disease caused by P. noxium. Among the treatments, complete elimination of the pathogen was observed when the BCAs were applied as a consortium. In addition, the BCAs used in this study promoted the plant growth. Therefore, Trichoderma and streptomycetes consortium could be used as a potential biocontrol measure to manage P. noxium infections in the field over the application of hazardous chemical control measures. [ABSTRACT FROM AUTHOR]

From the intestines of millipedes of the species Nedyopus dawydoffiae and Orthomorpha sp. (class Diplopoda) and from their food substrates (plant residues), 72 bacterial strains belonging to 25 genera were isolated and identified. Among the studied strains, actinobacteria predominated, among which streptomycetes were the most numerous, although representatives of 14 other genera of actinobacteria were also present. High abundance of actinobacteria with antimicrobial activity was noted, including members of the "rare" genera Actinoplanes, Amycolatopsis, Kitasatospora, Lechevalieria, Micromonospora, Nocardiopsis, and Saccharopolyspora. This is the first report on antimicrobial activity in Kitasatospora saccharophila INA 01226 and Nocardiopsis umidischolae INA 01230. Heterogeneity in terms of antibiotic formation in the populations of Streptomyces pratensis and S. termitum was shown. The most promising bacterial strains chosen for the chemical study of antibiotics formed exhibited activity against methicillin-resistant Staphylococcus aureus INA 00761 (MRSA) and vancomycin-resistant strain Leuconostoc mesenteroides VKPM B-4177 (VRLM). [ABSTRACT FROM AUTHOR]

For many decades, members in the genus Streptomyces have been considered the principal microbial producers of secondary metabolites with antibiotic activity. In this study, we evaluated the inhibitory activity of a cell-free supernatant produced by Streptomyces sp. CACIS1.16CA against human and plant bacterial pathogens. We also assessed the thermal stability of the compounds. An initial screening to evaluate the antibacterial activity of compounds diffused from a CACIS-1.16CA culture into agar discs found inhibitory effects against Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus pumilus, and Pectobacterium carotovorum. A cell-free supernatant from cultured CACIS-1.16CA confirmed the inhibition effects on the susceptible pathogens. Thermally treating the supernatant did not significantly affect the inhibitory activity, indicating Streptomyces sp. CACIS-1.16CA produces some thermally stable antibacterial metabolites. This antibacterial activity is consistent with the detection of biosynthetic gene clusters for polyketide synthase Types I and II and non-ribosomal peptide synthase. [ABSTRACT FROM AUTHOR]

Forty streptomycetes were isolated from the soils of farms in Riyadh. Only three isolates (St-2, St-9, and St-25) exhibited cellulolytic-ligninolytic activity, with the St-9 isolate exhibiting the highest activity and identified as Streptomyces lazureus. the optimum environmental and nutritional conditions for maximum cellulolytic-ligninolytic activity were determined as fermentation batch of pH of 7.5, inoculum size of 200 µl of bacterial suspension, incubation period of 7 d, and incubation temperature of 30°C. in addition, the fermentation batch contained peptone and yeast extract as the best nitrogen and carbon sources, respectively. Cellulase and ligninase were purified via gel filtration column chromatography. the accumulated end-product of the fermentation process was glucose powder, which was subjected to a partial characterization process. the glucose powder appeared white, melted at 146°C, was highly soluble in water, slightly soluble in ethanol, and insoluble in ethyl ether. the glucose solution appeared clear without precipitates and had a low electric conductivity of 15 µS.cm-1. [ABSTRACT FROM AUTHOR]

Actinomycetes are the most prominent group of microorganisms that produce biologically active compounds. Among them, special attention is focused on bacteria in the genus Streptomyces. Streptomycetes are an important source of biologically active natural compounds that could be considered therapeutic agents. In this study, we described the identification, purification, and structure elucidation of two new naphthoquinone-based meroterpenoids, furaquinocins K and L, from Streptomyces sp. Je 1-369 strain, which was isolated from the rhizosphere soil of Juniperus excelsa (Bieb.). The main difference between furaquinocins K and L and the described furaquinocins was a modification in the polyketide naphthoquinone skeleton. In addition, the structure of furaquinocin L contained an acetylhydrazone fragment, which is quite rare for natural compounds. We also identified a furaquinocin biosynthetic gene cluster in the Je 1-369 strain, which showed similarity (60%) with the furaquinocin B biosynthetic gene cluster from Streptomyces sp. KO-3988. Furaquinocin L showed activity against Gram-positive bacteria without cytotoxic effects. [ABSTRACT FROM AUTHOR]

Pyrrhoderma noxium is a plant fungal pathogen that induces the disease of brown root rot in a large variety of tree species. It is currently infecting many of the amenity trees within Brisbane City of Queensland, Australia. Steering away from harmful chemical fungicides, biological control agents offer environmentally friendly alternatives. Streptomycetes are known for their production of novel bioactive secondary metabolites with biocontrol potential, particularly, streptomycete symbionts isolated from unique ecological niches. In this study, 37 termite gut-associated actinomycete isolates were identified using molecular methods and screened against P. noxium. A majority of the isolates belonged to the genus Streptomyces, and 15 isolates exhibited strong antifungal activity with up to 98.5% mycelial inhibition of the fungal pathogen. MS/MS molecular networking analysis of the isolates’ fermentation extracts revealed several chemical classes with polyketides being among the most abundant. Most of the metabolites, however, did not have matches to the GNPS database, indicating potential novel antifungal compounds in the active extracts obtained from the isolates. Pathway enrichment and overrepresentation analyses revealed pathways relating to polyketide antibiotic production, among other antibiotic pathways, further confirming the biosynthetic potential of the termite gut-associated streptomycetes with biocontrol potential against P. noxium.

There is a real consensus that new antibiotics are urgently needed and are the best chance for combating antibiotic resistance. The phylum Actinobacteria is one of the main producers of new antibiotics, with a recent paradigm shift whereby rare actinomycetes have been increasingly targeted as a source of new secondary metabolites for the discovery of new antibiotics. However, this review shows that the genus Streptomyces is still the largest current producer of new and innovative secondary metabolites. Between January 2015 and December 2020, a significantly high number of novel Streptomyces spp. have been isolated from different environments, including extreme environments, symbionts, terrestrial soils, sediments and also from marine environments, mainly from marine invertebrates and marine sediments. This review highlights 135 new species of Streptomyces during this 6-year period with 108 new species of Streptomyces from the terrestrial environment and 27 new species from marine sources. A brief summary of the different pre-treatment methods used for the successful isolation of some of the new species of Streptomyces is also discussed, as well as the biological activities of the isolated secondary metabolites. A total of 279 new secondary metabolites have been recorded from 121 species of Streptomyces which exhibit diverse biological activity. The greatest number of new secondary metabolites originated from the terrestrial-sourced Streptomyces spp. [ABSTRACT FROM AUTHOR]

Biomineral formation is a common trait and prominent for soil Actinobacteria, including the genus Streptomyces. We investigated the formation of nickel-containing biominerals in the presence of a heavy-metal-resistant Streptomyces mirabilis P16B-1. Biomineralization was found to occur both in solid and liquid media. Minerals were identified with Raman spectroscopy and TEM-EDX to be either Mg-containing struvite produced in media containing no nickel, or Ni-struvite where Ni replaces the Mg when nickel was present in sufficient concentrations in the media. The precipitation of Ni-struvite reduced the concentration of nickel available in the medium. Therefore, Ni-struvite precipitation is an efficient mechanism for tolerance to nickel. We discuss the contribution of a plasmid-encoded nickel efflux transporter in aiding biomineralization. In the elevated local concentrations of Ni surrounding the cells carrying this plasmid, more biominerals occurred supporting this point of view. The biominerals formed have been quantified, showing that the conditions of growth do influence mineralization. This control is also visible in differences observed to biosynthetically synthesized Ni-struvites, including the use of sterile-filtered culture supernatant. The use of the wildtype S. mirabilis P16B-1 and its plasmid-free derivative, as well as a metal-sensitive recipient, S. lividans, and the same transformed with the plasmid, allowed us to access genetic factors involved in this partial control of biomineral formation. [ABSTRACT FROM AUTHOR]

Anthracnose is a cosmopolitan fungal disease affecting many tropical and subtropical plants and was first associated with the members of the genus Colletotrichum. In this study, we evaluated the potential antifungal activity of Streptomyces sp. AGS-58 to inhibit anthracnose-causing Colletotrichum spp. on mango fruits. Additionally, a goal of this study was to investigate if the extracellular metabolites produced by the AGS-58 strain could inhibit fungal conidial germination in vitro and control post-harvest anthracnose disease on mango fruits. Antagonistic streptomycetes were initially isolated from Jalapeño chili pepper soil fields and were preliminary selected for their antagonism against C. siamense. The isolate identified as Streptomyces sp. AGS-58 exhibited the highest inhibitory activity against C. siamense CT1. The metabolites obtained from the excreted droplets that accumulated on AGS-58 colonies were studied for their inhibitory effect on conidial germination. According to morphological evidence, extracellular exudates inhibited conidial germ tube formation and hyphal extension. These results suggest that the exudate contains antifungal metabolites that can inhibit the growth of C. siamense. The inhibitory activity was similar to that of Benlate. Spraying mango fruits with the extracellular exudate affected the germination of C. siamense conidia and thus prevented anthracnose progression. To the best of our knowledge, this study suggests the potential of Streptomyces sp. AGS-58 and its extracellular secondary metabolites in controlling anthracnose-causing fungi that infect post-harvest fruits. [ABSTRACT FROM AUTHOR]

The use of chemical fertilizers and pesticides has caused harmful impacts on the environment with the increase in economic burden. Biofertilizers are biological products containing living microorganisms capable of improving plant growth through eco-friendly mechanisms. In this work, three actinobacterial strains Streptomyces violaceoruber, Streptomyces coelicolor, and Kocuria rhizophila were characterized for multiple plant growth promoting (PGP) traits such as indole acetic acid production, phosphate solubilization, N2-fixation, and drought and salt tolerance. Then, these strains were investigated for their secreted and cellular metabolome, revealing a rich arsenal of bioactive molecules, including antibiotics and siderophores, with S. violaceoruber being the most prolific strain. Furthermore, the in vivo assays, performed on tomato (Solanum lycopersicum L.), resulted in an improved germination index and the growth of seedlings from seeds treated with PGP actinobacteria, with a particular focus on S. violaceoruber cultures. In particular, this last strain, producing volatile organic compounds having antimicrobial activity, was able to modulate volatilome and exert control on the global DNA methylation of tomato seedlings. Thus, these results, confirming the efficacy of the selected actinobacteria strains in promoting plant growth and development by producing volatile and non-volatile bioactive molecules, can promote eco-friendly alternatives in sustainable agriculture.

Beneficial endophytes are key factors in plant productivity and disease control; therefore, research is ongoing to characterize the potential of endophytes as microbial inoculants to promote plant growth and act as biocontrol agents. In this study, we searched for and identified a set of endophytes occurring naturally in a few important crops. Beneficial endophytes were shown to antagonize several important fungi and bacteria, in particular those affecting tomato (Solanum lycopersicum), including Rhizoctonia solani, Alternaria alternata, Clavibacter michiganensis pv. michiganensis, Ralstonia solanacearum, and Xanthomonas vesicatoria. We characterized the most promising as potential inoculants of tomato, aiming to foster plant growth and control the bacterial spot disease caused by Xanthomonas vesicatoria. Among the selected endophytes, we identified a novel streptomycetes, taxonomically related to Streptomyces avermitilis and a pseudomonad, identified as Pseudomonas granadensis. The beneficial effects of these two bacteria, used as single inoculants or as a combination of both, were seen in a significant increase in root and shoot length (approximately 31% and 34% for the streptomycetes and 18% and 16% for the pseudomonad) and dry root biomass (90% for the streptomycetes and 70% for the pseudomonad). Additionally, both inoculants reduced disease progression and severity following inoculation with X. vesicatoria. There was no significant difference between plants treated with single inoculants and plants treated with both. The penetration and efficient colonization of tomato tissues by a green fluorescent protein-tagged culture of the streptomycetes was observed by confocal microscopy, confirming its endophytic nature. [ABSTRACT FROM AUTHOR]

Streptomycetes have for a long time attracted attention of researchers in the fields of industrial microbiology, biotechnology and genetic engineering as producers of various nutrients. At present, almost 17 % of the biologically active of microbial secondary metabolites (about 7600 of the 43000 known) are isolated from streptomycetes. Nowadays, the products of streptomycete biosynthesis are used in various fields: in agriculture – for the treatment and prevention of bacterial and fungal infections, as growth stimulators and additives in animal feed, etc.; in the food industry – at canning of foodstuff with the maximum preservation of nutrients; in scientific research – to inhibit certain stages of biochemical transformations, cell destruction in order to isolate subcellular structures, in the cultivation of viruses, in genetic research, etc. Some of the main compounds that synthesize streptomycetes are enzymes, including hydrolytic, in particular proteinases, amylase, lipase, cellulase, DNAses, lytic enzymes and others. Lytic enzymes, by acting on the substrate, can be divided into bacteriolytic, myco- and yeast-elitic. Due to the lability of the enzymatic apparatus, members of the genus Streptomyces have a high antagonistic activity, which suppress the activity of other bacteria and fungi. Significant biosynthetic potential and incredible heterogeneity of streptomycetes determine the relevance of search for new producers and in-depth study of known microorganisms. Purpose: to determine the composition of enzymes in the culture liquid of strains; fractionation of protein complexes by gel filtration on Sephadex G-75 and comparison of their lytic activities. When determining the composition of enzymes in the culture fluid of the producers, it was found that all studied strains dissolved B. subtilis cells and only selected variants (S. recifensis 2P-15, P-29, 2.2 and 5.2) caused lysis of S. aureus cells. The yeast-lytic activity of streptomycetes was low, and in some strains (Streptomyces sp. 35, S. avermitilis AC-2179 and S. recifensis 6.2) it was not detected at all. The most active producer of proteinases was the rifampicin-resistant variant of S. recifensis 2P-15, and high amylolytic activity was demonstrated by variants of Streptomyces sp. 31, 2P-15 and P-29. Comparative analysis of lytic activity in the fractionation of enzymes on Sephadex G-75 showed that the most active is variant 2.2. It had the highest yield of staphylolytic activity for both high and low molecular weight proteins.Conclusions. Studies indicate a fairly high heterogeneity of the composition of enzyme complexes produced by streptomycetes. However, apparently, there are basic sets of genes encoding the most needful groups of enzymes, among which lytic enzymes, proteinases and amylase play an important role in the manifestation of antagonistic activity and food needs. Therefore, some of the studied strains can be use as objects for further optimization of enzyme synthesis, creation of overproducing strains and obtaining on their basis highly effective enzyme preparations.

Members of the genus Streptomyces are mycelial bacteria that undergo a complex life cycle that makes them similar to multicellular organisms. Streptomycetes are important industrial microorganisms, as they produce a plethora of medically relevant natural products, including the majority of clinically important antibiotics. This review addresses the morphogenesis of streptomycetes in submerged growth conditions in connection with the biosynthesis of antibiotics, as well as the events of programmed cell death in the course of the producer's development.

The review concerns discussion of certain aspects of growth and development of streptomycetes, that have an adaptation meaning for their existence under natural conditions and reflect our perception of them as procaryotes which have a range of qualities typical of multicellular organisms. At present, the concept of multicellularity is the key idea in investigation of growth processes, differentiation and physiology of streptomycetes. Streptomyces olivocinereus is presented as an effective model that gives the unique opportunities for investigation of different aspects of biology of streptomycetes within laboratory environment as well as in natural environment in suti. S.olivocinereus produces luminescent antibiotic geliomycin (resistomycin). In this review we summarized the results of the many years of investigation of growth, differentiation and behavior of this streptomycete. The investigations were undertaken by a group of scientists of the Moscow State University. The results can be employed as arguments for the multicellular nature of streptomycetes.

Streptomycetes, soil-dwelling mycelial bacteria, can form biofilms as indigenous components of the environment. The biofilms formed by streptomycetes exist in different ecological niches, in natural, medical, industrial environments. The biofilm-forming streptomycetes affect water quality, human health, associate with deterioration of artworks and historical monuments. The review should be of interest for researchers of the biofilm mode of streptomycetes growth.

Addition of perfluorodecalin with gas-transporting function to the liquid medium during submerged cultivation of actinomycetes of the genus Streptomyces resulted in higher intensity and level of the biomass synthesis and increased production of streptomycin and daunorubicin. Addition of perfluorodecalin to the medium provided a 2.0-2.3-fold surpass of the maximum antibiotic production (achieved by the 120th-144th hours of the culture growth) vs. the antibiotic accumulation peaks in the control.

Abstract Background Production of antibiotics to inhibit competitors affects soil microbial community composition and contributes to disease suppression. In this work, we characterized whether Streptomyces bacteria, prolific antibiotics producers, inhibit a soil borne human pathogenic microorganism, Streptomyces sudanensis. S. sudanensis represents the major causal agent of actinomycetoma – a largely under-studied and dreadful subcutaneous disease of humans in the tropics and subtropics. The objective of this study was to evaluate the in vitro S. sudanensis inhibitory potential of soil streptomycetes isolated from different sites in Sudan, including areas with frequent (mycetoma belt) and rare actinomycetoma cases of illness. Results Using selective media, 173 Streptomyces isolates were recovered from 17 sites representing three ecoregions and different vegetation and ecological subdivisions in Sudan. In total, 115 strains of the 173 (66.5%) displayed antagonism against S. sudanensis with different levels of inhibition. Strains isolated from the South Saharan steppe and woodlands ecoregion (Northern Sudan) exhibited higher inhibitory potential than those strains isolated from the East Sudanian savanna ecoregion located in the south and southeastern Sudan, or the strains isolated from the Sahelian Acacia savanna ecoregion located in central and western Sudan. According to 16S rRNA gene sequence analysis, isolates were predominantly related to Streptomyces werraensis, S. enissocaesilis, S. griseostramineus and S. prasinosporus. Three clusters of isolates were related to strains that have previously been isolated from human and animal actinomycetoma cases: SD524 (Streptomyces sp. subclade 6), SD528 (Streptomyces griseostramineus) and SD552 (Streptomyces werraensis). Conclusion The in vitro inhibitory potential against S. sudanensis was proven for more than half of the soil streptomycetes isolates in this study and this potential may contribute to suppressing the abundance and virulence of S. sudanensis. The streptomycetes isolated from the mycetoma free South Saharan steppe ecoregion show the highest average inhibitory potential. Further analyses suggest that mainly soil properties and rainfall modulate the structure and function of Streptomyces species, including their antagonistic activity against S. sudanensis.

The Brown root rot pathogen Pyrrhoderma noxium (Corner) L.W. Zhou and Y.C. Dai is known to infect a large number of culturally and economically important plant species across the world. Although chemical control measures have been effective in managing this pathogen, their adverse effects on the ecosystem have limited their use. The use of biological control agents (BCAs) thus is generally accepted as an environmentally friendly way of managing various pathogens. Testing various consortia of the BCAs with different antagonistic mechanisms may even provide better disease protection than the use of a single BCA against aggressive plant pathogens such as the P. noxium. In the presented study, the wood decay experiment and the pot trial confirmed that the consortium of Trichoderma strains (#5029 and 5001) and streptomycetes (#USC−6914 and #USC−595-B) used was effective in protecting wood decay and plant disease caused by P. noxium. Among the treatments, complete elimination of the pathogen was observed when the BCAs were applied as a consortium. In addition, the BCAs used in this study promoted the plant growth. Therefore, Trichoderma and streptomycetes consortium could be used as a potential biocontrol measure to manage P. noxium infections in the field over the application of hazardous chemical control measures.

Actinomycetes are the most prominent group of microorganisms that produce biologically active compounds. Among them, special attention is focused on bacteria in the genus Streptomyces. Streptomycetes are an important source of biologically active natural compounds that could be considered therapeutic agents. In this study, we described the identification, purification, and structure elucidation of two new naphthoquinone-based meroterpenoids, furaquinocins K and L, from Streptomyces sp. Je 1-369 strain, which was isolated from the rhizosphere soil of Juniperus excelsa (Bieb.). The main difference between furaquinocins K and L and the described furaquinocins was a modification in the polyketide naphthoquinone skeleton. In addition, the structure of furaquinocin L contained an acetylhydrazone fragment, which is quite rare for natural compounds. We also identified a furaquinocin biosynthetic gene cluster in the Je 1-369 strain, which showed similarity (60%) with the furaquinocin B biosynthetic gene cluster from Streptomyces sp. KO-3988. Furaquinocin L showed activity against Gram-positive bacteria without cytotoxic effects.

Tuberculosis (TB) is still a global disease threatening people’s lives. With the emergence of multi-drug-resistant Mycobacterium tuberculosis the prevention and control of tuberculosis faces new challenges, and the burden of tuberculosis treatment is increasing among the world. Ilamycins are novel cyclopeptides with potent anti-TB activities, which have a unique target protein against M. tuberculosis and drug-resistant strains. Herein, ilamycin F, a major secondary metabolite isolated from the marine-derived mutant strain Streptomyces atratus SCSIO ZH16 ΔilaR, is used as a scaffold to semi-synthesize eighteen new ilamycin derivatives (ilamycin NJL1–NJL18, 1–18). Our study reveals that four of ilamycin NJLs (1, 6, 8, and 10) have slightly stronger anti-TB activities against Mtb H37Rv (minimum inhibitory concentration, 1.6–1.7 μM) compared with that of ilamycin F on day 14th, but obviously display more potent activities than ilamycin F on day 3rd, indicating anti-TB activities of these derivatives with fast-onset effect. In addition, cytotoxic assays show most ilamycin NJLs with low cytotoxicity except ilamycin NJL1 (1). These findings will promote the further exploration of structure-activity relationships for ilamycins and the development of anti-TB drugs.

Abstract Background Streptomycetes are filamentous microorganisms of high biotechnological relevance, especially for the production of antibiotics. In submerged cultures, the productivity of these microorganisms is closely linked to their growth morphology. Microfluidic lab-on-a-chip cultivation systems, coupled with automated time-lapse imaging, generate spatio-temporal insights into the mycelium development of streptomycetes, therewith extending the biotechnological toolset by spatio-temporal screening under well-controlled and reproducible conditions. However, the analysis of the complex mycelial structure formation is limited by the extent of manual interventions required during processing of the acquired high-volume image data. These interventions typically lead to high evaluation times and, therewith, limit the analytic throughput and exploitation of microfluidic-based screenings. Results We present the tool mycelyso (MYCElium anaLYsis SOftware), an image analysis system tailored to fully automated hyphae-level processing of image stacks generated by time-lapse microscopy. With mycelyso, the developing hyphal streptomycete network is automatically segmented and tracked over the cultivation period. Versatile key growth parameters such as mycelium network structure, its development over time, and tip growth rates are extracted. Results are presented in the web-based exploration tool mycelyso Inspector, allowing for user friendly quality control and downstream evaluation of the extracted information. In addition, 2D and 3D visualizations show temporal tracking for detailed inspection of morphological growth behaviors. For ease of getting started with mycelyso, bundled Windows packages as well as Docker images along with tutorial videos are available. Conclusion mycelyso is a well-documented, platform-independent open source toolkit for the automated end-to-end analysis of Streptomyces image stacks. The batch-analysis mode facilitates the rapid and reproducible processing of large microfluidic screenings, and easy extraction of morphological parameters. The objective evaluation of image stacks is possible by reproducible evaluation workflows, useful to unravel correlations between morphological, molecular and process parameters at the hyphae- and mycelium-levels with statistical power.

Biomineral formation is a common trait and prominent for soil Actinobacteria, including the genus Streptomyces. We investigated the formation of nickel-containing biominerals in the presence of a heavy-metal-resistant Streptomyces mirabilis P16B-1. Biomineralization was found to occur both in solid and liquid media. Minerals were identified with Raman spectroscopy and TEM-EDX to be either Mg-containing struvite produced in media containing no nickel, or Ni-struvite where Ni replaces the Mg when nickel was present in sufficient concentrations in the media. The precipitation of Ni-struvite reduced the concentration of nickel available in the medium. Therefore, Ni-struvite precipitation is an efficient mechanism for tolerance to nickel. We discuss the contribution of a plasmid-encoded nickel efflux transporter in aiding biomineralization. In the elevated local concentrations of Ni surrounding the cells carrying this plasmid, more biominerals occurred supporting this point of view. The biominerals formed have been quantified, showing that the conditions of growth do influence mineralization. This control is also visible in differences observed to biosynthetically synthesized Ni-struvites, including the use of sterile-filtered culture supernatant. The use of the wildtype S. mirabilis P16B-1 and its plasmid-free derivative, as well as a metal-sensitive recipient, S. lividans, and the same transformed with the plasmid, allowed us to access genetic factors involved in this partial control of biomineral formation.

Aim: Research on prevention and cure of banana wilt is important to ensure the healthy development of the banana industry. In this study, antifungal mechanism of Streptomyces ma. FS‐4 on fusarium wilt of banana was investigated. Methods and Results: The physiological strain of banana fusarium pathogen Fusarium oxysporum f. sp. cubense Race 4 (FOC.4) was used as the target fungus, and the antifungal mechanism of the crude extract of Streptomyces ma. FS‐4 was investigated. Eighteen different compounds identified by gas chromatography–mass spectrometry were composed of aldehydes, methyl, hydrocarbons, amides, esters and acids. FS‐4 significantly inhibited the spore germination of the target fungi, with an EC50 of 22·78 μg ml−1. After treatment with 100 μg ml−1FS‐4 crude extract, the N‐acetylglucosamine content in the mycelium increased 1·95‐fold. However, the extract had no significant effect on β‐1,3‐glucanase. At the FS‐4 crude extract dose of 100 μg ml−1, the total sugar and protein contents decreased by 28·6 and 29·1% respectively, and the fat content was 41·3%. FS‐4 significantly inhibited the activity of the mitochondrial complex III of Foc4, which was reduced by 52·45%. Moreover FS‐4 reduced the activity of succinate dehydrogenase, a key enzyme in the Krebs cycle, by 60·2%. However, FS‐4 had no significant effect on malate dehydrogenase. The membrane potential on the mitochondrial inner membrane was significantly reduced at the test concentration of 100 μg ml−1. ROS gradually accumulated in the Foc4 hypha, and the burst was 3·97 times higher than the control. Conclusions: This study demonstrated that the antifungal mechanism of Streptomyces ma. FS‐4 against Foc4 includes the destruction of the plasma membrane and mitochondrial dysfunction and finally induction of cell apoptosis. Significance and Impact of the Study: These results may indicate the prevention and control of banana wilt, which is of great significance to the healthy development of banana industry system. [ABSTRACT FROM AUTHOR]

Enzymes are increasingly applied as biocatalysts for fulfilling industrial needs in a variety of applications and there is a bursting of interest for novel therapeutic proteins. Consequently, developing appropriate expression platforms for efficiently producing such recombinant proteins represents a crucial challenge. It is nowadays widely accepted that an ideal ‘universal microbial host’ for heterologous protein expression does not exist. Indeed, the first-choice microbes, as Escherichia coli or yeasts, possess known intrinsic limitations that inevitably restrict their applications. In this scenario, bacteria belonging to the Streptomyces genus need to be considered with more attention as promising, alternative, and versatile platforms for recombinant protein production. This is due to their peculiar features, first-of-all their natural attitude to secrete proteins in the extracellular milieu. Additionally, streptomycetes are considered robust and scalable industrial strains and a wide range of tools for their genetic manipulation is nowadays available. This mini-review includes an overview of recombinant protein production in streptomycetes, covering nearly 100 cases of heterologous proteins expressed in these Gram-positives from the 1980s to December 2019. We investigated homologous sources, heterologous hosts, and molecular tools (promoters/vectors/signal peptides) used for the expression of these recombinant proteins. We reported on their final cellular localization and yield. Thus, this analysis might represent a useful source of information, showing pros and cons of using streptomycetes as platform for recombinant protein production and paving the way for their more extensive use in future as alternative heterologous hosts.

Streptomycetes or mycelial microorganisms are able to form biofilms under the natural, industrial and clinical conditions. The controlled use of biofilms in various industrial processes is much more efficient vs. the cultivation of plankton suspended cells. Optimization of biotechnological processes with the use of streptomycete biofilms is advisable in production of lactic acid and detoxication of the liquor in pyrolysis of plant biomass. Streptomycete biofilms are used in water purification systems. It is recommended to use biofilms for detoxication of wastes and bioremediation of soils contaminated with hard metals. The use of biofilms of streptomycetes producing biologically active substances is of special interest. High yields of antibiotics and actinomycin D in particular was observed with cultivation of antibioc-producing streptomycetes as biofilms in bioreactors of unique design.

The study has an objective of isolating and characterizing suspected Streptomycetes with the potential to decompose organic compounds in arable soil. The isolates were grown on a culture media and a total of 61 slopes were inoculated and labeled using the following characterization tests: catalase test, gram staining, oxidase test, motility test, and oxidative-fermentative test. After characterization tests, data generated in the laboratory were analyzed and the study showed that isolates A2 (c, e), B2 (c), C1 (b), C2 (a), D1 (e) and D2 (d) were suspected to be Streptomycetes species. Isolates D1 (d) and D2 (b) were suspected to be Escherichia coli while isolates A1 (a), B2 (a, b) and D1 (a) were suspected to be Bacillus species. Isolates A1 (b), C1 (a), D1 (c), D2 (e) were suspected to be Pseudomonas species. Further identification showed that isolates A2 (d) and B1 (b) could be Enterobacter species while isolates A2 (a, b) were suspected to be Klebsiella species. The study tentatively identified Streptomycetes species; Escherichia coli; Bacillus species; Enterobacter species; Pseudomonas species and Klebsiella species. The suspected Streptomycetes identified were considered as potential organic matter decomposers in arable soil.

Gastrointestinal lipase inhibitors are molecules of pharmaceutical interest due to their use as anti-obesity drugs. In this study, forty strains isolated from soil and sediments were identified with the ability to produce inhibition of gastrointestinal lipase activity. The biomass extract of these strains showed at least 50% inhibition in the hydrolysis of tributyrin by recombinant human pancreatic lipase (rHPL) or rabbit gastric lipase (RGL) by in vitro assays. Based on gene sequencing, the isolates were identified mainly as Streptomycetes. Moreover, none of the identified strains has been reported to be lipase inhibitor producers, so they can be viewed as potential sources for obtaining new drugs. IC50 values of the three best inhibitor extracts showed that AC104-10 was the most promising strain for production of gastrointestinal lipase inhibitors. AC104-10 shows 99% homology (16S rRNA gene fragment) to Streptomyces cinereoruber strain NBRC 12756. An inhibitory study over trypsin activity revealed that AC104-10 extract, as well as THL, had no significant effect on the activity of this protease, showing its specificity for lipases. In addition, analyzes by MALDI-TOF mass spectrometry of the enzyme-inhibitor complex revealed that there is a covalent interaction of the AC104-10 inhibitor with the catalytic serine of the pancreatic lipase, and that the molecular weight of the inhibitor is approximately 686.19 Da. [ABSTRACT FROM AUTHOR]

In this paper, we aimed at assessing the best conditions for the isolation of actinobacteria from old potato samples. A set of media and pretreatments were tested. The optimal were chosen for the isolation of actinobacteria from potatoes from Peru, Chile and Argentina. Isolates were tested on the presence of thaxtomin phytotoxin by amplification of the respective gene. Phylogenetic position of strains was compared with their geographical origin, pathogenic potential and existence of common scab (CS) symptoms on potato sample. We demonstrated that RNAlater can be successfully used for the long-term preservation of potato peel for subsequent isolation of actinobacteria on R2A medium. Many streptomycetes were thaxtomin-positive, though they are distantly-related to described pathogens causing CS. Genus Nocardia was first reported to be thaxtomin-positive. Potentially pathogenic strains were isolated not only from infected potato but also from those lacking CS symptoms. Some strains from scabby potatoes were thaxtomin-negative. [ABSTRACT FROM AUTHOR]