Search

Abstract Background The search for new bioactive natural compounds with anticancer activity is still of great importance. Even though their potential for diagnostics and treatment of cancer has already been proved, the availability is still limited. Hypericin, a naphthodianthrone isolated essentially from plant source Hypericum perforatum L. along with other related anthraquinones and bisanthraquinones belongs to this group of compounds. Although it has been proven that hypericin is synthesized by the polyketide pathway in plants, none of the candidate genes coding for key enzymes has been experimentally validated yet. Despite the rare occurrence of anthraquinones in plants, their presence in microorganisms, including endophytic fungi, is quite common. Unlike plants, several biosynthetic genes grouped into clusters (BGCs) in fungal endophytes have already been characterized. Results The aim of this work was to predict, identify and characterize the anthraquinone BGCs in de novo assembled and functionally annotated genomes of selected endophytic fungal isolates (Fusarium oxysporum, Plectosphaerella cucumerina, Scedosporium apiospermum, Diaporthe eres, Canariomyces subthermophilus) obtained from different tissues of Hypericum spp. The number of predicted type I polyketide synthase (PKS) BGCs in the studied genomes varied. The non-reducing type I PKS lacking thioesterase domain and adjacent discrete gene encoding protein with product release function were identified only in the genomes of C. subthermophilus and D. eres. A candidate bisanthraquinone BGC was predicted in C. subthermophilus genome and comprised genes coding the enzymes that catalyze formation of the basic anthraquinone skeleton (PKS, metallo-beta-lactamase, decarboxylase, anthrone oxygenase), putative dimerization enzyme (cytochrome P450 monooxygenase), other tailoring enzymes (oxidoreductase, dehydrogenase/reductase), and non-catalytic proteins (fungal transcription factor, transporter protein). Conclusions The results provide an insight into genetic background of anthraquinone biosynthesis in Hypericum-borne endophytes. The predicted bisanthraquinone gene cluster represents a basis for functional validation of the candidate biosynthetic genes in a simple eukaryotic system as a prospective biotechnological alternative for production of hypericin and related bioactive anthraquinones.

Background: The search for new bioactive natural compounds with anticancer activity is still of great importance. Even though their potential for diagnostics and treatment of cancer has already been proved, the availability is still limited. Hypericin, a naphthodianthrone isolated essentially from plant source Hypericum perforatum L. along with other related anthraquinones and bisanthraquinones belongs to this group of compounds. Although it has been proven that hypericin is synthesized by the polyketide pathway in plants, none of the candidate genes coding for key enzymes has been experimentally validated yet. Despite the rare occurrence of anthraquinones in plants, their presence in microorganisms, including endophytic fungi, is quite common. Unlike plants, several biosynthetic genes grouped into clusters (BGCs) in fungal endophytes have already been characterized. Results: The aim of this work was to predict, identify and characterize the anthraquinone BGCs in de novo assembled and functionally annotated genomes of selected endophytic fungal isolates (Fusarium oxysporum, Plectosphaerella cucumerina, Scedosporium apiospermum, Diaporthe eres, Canariomyces subthermophilus) obtained from different tissues of Hypericum spp. The number of predicted type I polyketide synthase (PKS) BGCs in the studied genomes varied. The non-reducing type I PKS lacking thioesterase domain and adjacent discrete gene encoding protein with product release function were identified only in the genomes of C. subthermophilus and D. eres. A candidate bisanthraquinone BGC was predicted in C. subthermophilus genome and comprised genes coding the enzymes that catalyze formation of the basic anthraquinone skeleton (PKS, metallo-beta-lactamase, decarboxylase, anthrone oxygenase), putative dimerization enzyme (cytochrome P450 monooxygenase), other tailoring enzymes (oxidoreductase, dehydrogenase/reductase), and non-catalytic proteins (fungal transcription factor, transporter protein). Conclusions: The results provide an insight into genetic background of anthraquinone biosynthesis in Hypericum-borne endophytes. The predicted bisanthraquinone gene cluster represents a basis for functional validation of the candidate biosynthetic genes in a simple eukaryotic system as a prospective biotechnological alternative for production of hypericin and related bioactive anthraquinones. [ABSTRACT FROM AUTHOR]

1-deoxynojirimycin (DNJ), a piperidine iminosugar analogous to D-glucose, exhibits various biological properties with antidiabetic, antiviral, anti-inflammatory, and antimicrobial effects. N -alkylated DNJ derivatives have been used clinically as medicines for type 2 diabetes and lysosomal storage diseases. DNJ naturally occurs in plants and microbes, and the methods of DNJ production in these organisms have attained stereoselectivity with more environmentally friendly and simpler processes than chemical synthesis. However, the yield of DNJ has to be improved by reinforcing its biosynthetic pathway. This review summarizes the various DNJ-producing species and the production titer of DNJ in plants and microbes. Additionally, it compares the methods used to validate the biosynthesis of DNJ in plants and in microbes. It also covers the application of some DNJ biosynthesis-related genes and the enhancement of DNJ content via metabolic engineering. Finally, this review highlights new biological sources of other iminosugars that can be detected through the knowledge of DNJ biosynthesis. [Display omitted] • Deoxynojirimycin (DNJ) is a piperidine iminosugar with medicinal properties. • DNJ is naturally found in mulberry plants and Bacillus and Streptomyces spp. • DNJ yield can be improved with the discovery of genes involved in its biosynthesis. • Biological production of new iminosugar can be identified via DNJ biosynthetic genes. [ABSTRACT FROM AUTHOR]

Deep-sea environments, as relatively unexplored extremes within the Earth's biosphere, exhibit notable distinctions from terrestrial habitats. To thrive in these extreme conditions, deep-sea actinomycetes have evolved unique biochemical metabolisms and physiological capabilities to ensure their survival in this niche. In this study, five actinomycetes strains were isolated and identified from the Mariana Trench via the culture-dependent method and 16S rRNA sequencing approach. The antimicrobial activity of Microbacterium sp. B1075 was found to be the most potent, and therefore, it was selected as the target strain. Molecular networking analysis via the Global Natural Products Social Molecular Networking (GNPS) platform identified 25 flavonoid compounds as flavonoid secondary metabolites. Among these, genistein was purified and identified as a bioactive compound with significant antibacterial activity. The complete synthesis pathway for genistein was proposed within strain B1075 based on whole-genome sequencing data, with the key gene being CHS (encoding chalcone synthase). The expression of the gene CHS was significantly regulated by high hydrostatic pressure, with a consequent impact on the production of flavonoid compounds in strain B1075, revealing the relationship between actinomycetes' synthesis of flavonoid-like secondary metabolites and their adaptation to high-pressure environments at the molecular level. These results not only expand our understanding of deep-sea microorganisms but also hold promise for providing valuable insights into the development of novel pharmaceuticals in the field of biopharmaceuticals. [ABSTRACT FROM AUTHOR]

Abstract Background Microbial secondary metabolites play a crucial role in the intricate interactions within the natural environment. Among these metabolites, ribosomally synthesized and post-translationally modified peptides (RiPPs) are becoming a promising source of therapeutic agents due to their structural diversity and functional versatility. However, their biosynthetic capacity and ecological functions remain largely underexplored. Results Here, we aim to explore the biosynthetic profile of RiPPs and their potential roles in the interactions between microbes and viruses in the ocean, which encompasses a vast diversity of unique biomes that are rich in interactions and remains chemically underexplored. We first developed TrRiPP to identify RiPPs from ocean metagenomes, a deep learning method that detects RiPP precursors in a hallmark gene-independent manner to overcome the limitations of classic methods in processing highly fragmented metagenomic data. Applying this method to metagenomes from the global ocean microbiome, we uncover a diverse array of previously uncharacterized putative RiPP families with great novelty and diversity. Through correlation analysis based on metatranscriptomic data, we observed a high prevalence of antiphage defense-related and phage-related protein families that were co-expressed with RiPP families. Based on this putative association between RiPPs and phage infection, we constructed an Ocean Virus Database (OVD) and established a RiPP-involving host-phage interaction network through host prediction and co-expression analysis, revealing complex connectivities linking RiPP-encoding prokaryotes, RiPP families, viral protein families, and phages. These findings highlight the potential of RiPP families involved in prokaryote-phage interactions and coevolution, providing insights into their ecological functions in the ocean microbiome. Conclusions This study provides a systematic investigation of the biosynthetic potential of RiPPs from the ocean microbiome at a global scale, shedding light on the essential insights into the ecological functions of RiPPs in prokaryote-phage interactions through the integration of deep learning approaches, metatranscriptomic data, and host-phage connectivity. This study serves as a valuable example of exploring the ecological functions of bacterial secondary metabolites, particularly their associations with unexplored microbial interactions. Video Abstract

Background: Microbial secondary metabolites play a crucial role in the intricate interactions within the natural environment. Among these metabolites, ribosomally synthesized and post-translationally modified peptides (RiPPs) are becoming a promising source of therapeutic agents due to their structural diversity and functional versatility. However, their biosynthetic capacity and ecological functions remain largely underexplored. Results: Here, we aim to explore the biosynthetic profile of RiPPs and their potential roles in the interactions between microbes and viruses in the ocean, which encompasses a vast diversity of unique biomes that are rich in interactions and remains chemically underexplored. We first developed TrRiPP to identify RiPPs from ocean metagenomes, a deep learning method that detects RiPP precursors in a hallmark gene-independent manner to overcome the limitations of classic methods in processing highly fragmented metagenomic data. Applying this method to metagenomes from the global ocean microbiome, we uncover a diverse array of previously uncharacterized putative RiPP families with great novelty and diversity. Through correlation analysis based on metatranscriptomic data, we observed a high prevalence of antiphage defense-related and phage-related protein families that were co-expressed with RiPP families. Based on this putative association between RiPPs and phage infection, we constructed an Ocean Virus Database (OVD) and established a RiPP-involving host-phage interaction network through host prediction and co-expression analysis, revealing complex connectivities linking RiPP-encoding prokaryotes, RiPP families, viral protein families, and phages. These findings highlight the potential of RiPP families involved in prokaryote-phage interactions and coevolution, providing insights into their ecological functions in the ocean microbiome. Conclusions: This study provides a systematic investigation of the biosynthetic potential of RiPPs from the ocean microbiome at a global scale, shedding light on the essential insights into the ecological functions of RiPPs in prokaryote-phage interactions through the integration of deep learning approaches, metatranscriptomic data, and host-phage connectivity. This study serves as a valuable example of exploring the ecological functions of bacterial secondary metabolites, particularly their associations with unexplored microbial interactions. CSrTVep6AzTb_yem78LPYE Video Abstract [ABSTRACT FROM AUTHOR]

Introduction: The white-spotted flower chafer (Protaetia brevitarsis seulensis), which is widely distributed in Asian countries, is traditionally used in oriental medicine. However, its larvae are prone to severe damage by green muscardine disease (caused by Metarhizium anisopliae) during breeding. The aim of this study was to characterize Bacillus velezensis TJS119, which has been isolated from freshwater, and investigate its potential as a biocontrol agent against M. anisopliae in insects. Methods: TJS119 was obtained from freshwater samples in the Republic of Korea and was classified as B. velezensis. We evaluated its in vitro antifungal effect, sequenced the bacterial whole genome, mined genes responsible for the synthesis of secondary metabolites, performed secondary metabolite analysis Ultra performance liquid chromatography-mass spectrometry (UPLC-MS/MS), and conducted bioassays for determining green muscardine disease control ability. Results: Bacillus velezensis TJS119 inhibited the mycelial growth of M. anisopliae in vitro. The size of the B. velezensis TJS119 genome was estimated to be 3,890,913 bp with a GC content of 46.67% and 3,750 coding sequences. Biosynthetic gene clusters for secondary metabolites with antifungal activity were identified in the genome. Lipopeptides, including fengycin secreted by TJS119 exhibit antifungal activity. Application of TJS119 for the biocontrol against green muscardine disease increased the viability of white-spotted flower chafer by 94.7% compared to the control. Discussion: These results indicate that B. velezensis TJS119 is a potential biocontrol agent for insect pathogens. [ABSTRACT FROM AUTHOR]

The medicinal plants of the Asteraceae family are a valuable source of bioactive secondary metabolites, including polyphenols, phenolic acids, flavonoids, acetylenes, sesquiterpene lactones, triterpenes, etc. Under stressful conditions, the plants develop these secondary substances to carry out physiological tasks in plant cells. Secondary Asteraceae metabolites that are of the greatest interest to consumers are artemisinin (an anti-malarial drug from Artemisia annua L.—sweet wormwood), steviol glycosides (an intense sweetener from Stevia rebaudiana Bert.—stevia), caffeic acid derivatives (with a broad spectrum of biological activities synthesized from Echinacea purpurea (L.) Moench—echinacea and Cichorium intybus L.—chicory), helenalin and dihydrohelenalin (anti-inflammatory drug from Arnica montana L.—mountain arnica), parthenolide ("medieval aspirin" from Tanacetum parthenium (L.) Sch.Bip.—feverfew), and silymarin (liver-protective medicine from Silybum marianum (L.) Gaertn.—milk thistle). The necessity to enhance secondary metabolite synthesis has arisen due to the widespread use of these metabolites in numerous industrial sectors. Elicitation is an effective strategy to enhance the production of secondary metabolites in in vitro cultures. Suitable technological platforms for the production of phytochemicals are cell suspension, shoots, and hairy root cultures. Numerous reports describe an enhanced accumulation of desired metabolites after the application of various abiotic and biotic elicitors. Elicitors induce transcriptional changes in biosynthetic genes, leading to the metabolic reprogramming of secondary metabolism and clarifying the mechanism of the synthesis of bioactive compounds. This review summarizes biotechnological investigations concerning the biosynthesis of medicinally essential metabolites in plants of the Asteraceae family after various elicitor treatments. [ABSTRACT FROM AUTHOR]

Deep-sea environments, as relatively unexplored extremes within the Earth’s biosphere, exhibit notable distinctions from terrestrial habitats. To thrive in these extreme conditions, deep-sea actinomycetes have evolved unique biochemical metabolisms and physiological capabilities to ensure their survival in this niche. In this study, five actinomycetes strains were isolated and identified from the Mariana Trench via the culture-dependent method and 16S rRNA sequencing approach. The antimicrobial activity of Microbacterium sp. B1075 was found to be the most potent, and therefore, it was selected as the target strain. Molecular networking analysis via the Global Natural Products Social Molecular Networking (GNPS) platform identified 25 flavonoid compounds as flavonoid secondary metabolites. Among these, genistein was purified and identified as a bioactive compound with significant antibacterial activity. The complete synthesis pathway for genistein was proposed within strain B1075 based on whole-genome sequencing data, with the key gene being CHS (encoding chalcone synthase). The expression of the gene CHS was significantly regulated by high hydrostatic pressure, with a consequent impact on the production of flavonoid compounds in strain B1075, revealing the relationship between actinomycetes’ synthesis of flavonoid-like secondary metabolites and their adaptation to high-pressure environments at the molecular level. These results not only expand our understanding of deep-sea microorganisms but also hold promise for providing valuable insights into the development of novel pharmaceuticals in the field of biopharmaceuticals.

Multi-modular enzyme complexes known as non-ribosomal peptide synthetases (NRPSs) and polyketide synthetases (PKSs) have been widely reported in bacteria that produce secondary bioactive metabolites such as non-ribosomal peptides (NRPs) and polyketides (PKs), respectively. These NRPS/PKS pathways contribute to synthesizing several antibiotics, such as vancomycin, rifamycin, and bleomycin, which are vital in human medicine. The present study aimed to isolate gut-associated bacteria from mud crab Scylla serrata, and detect NRPS and PKS gene clusters associated with it. This study included 36 bacterial isolates from five mud crab gut samples. Biosynthetic gene clusters (NRPS and PKS), were detected by PCR using degenerative primers specific to these genes. Three isolates (FKP2–4, FKP4–1, and FKP2–16) were positive for NRPS and two for PKS (FKP2–4 and FKP4–1) genes. The isolates were subjected to 16S rRNA gene amplification and sequenced. In silico analysis of the sequences using the Basic Local Alignment Search Tool (BLAST) identified the isolates FKP2–4, FKP4–1, and FKP2–16 as Acinetobacter variabilis, Vagococcus fluvialis, and Staphylococcus arlettae, respectively, after comparing with the existing sequences available in the National Center for Biotechnology Information (NCBI) database. Compared to the control, it was observed that these isolates exhibited intriguing antagonistic activities against Escherichia coli and Staphylococcus aureus. However, these isolates failed to show significant activity against Candida albicans. Exopolysaccharide production by the isolated organisms was tested using Zobell marine agar (ZMA) with 5% sucrose, but none of the colonies were mucoid or slimy.

Iron is one of the highly abundant elements on the earth’s crust, an essential micronutrient for a majority of life forms, and exists in two frequent oxidation states such as ferrous (Fe2+) and ferric (Fe3+). These two oxidation states are interconvertible by redox reactions and form complexes with a wide range of siderophores. At neutral pH in soil, Fe2+ is highly soluble upto 100 mM but have less biological value, whereas Fe3+ is less soluble upto 10–9 M. This reduced bioavailability of Fe3+ induces competition among microorganisms. As many microorganisms need at least 10–6 M of Fe3+ form of iron for their growth, siderophores from these microbes readily withdraw Fe3+ iron from a variety of habitats for their survival. In this review, we bring into light the several recent investigations related to diverse chemistry of microbial siderophores, mechanisms of siderophore uptake, biosynthetic gene clusters in microbial genomes, various sources of heavy metal cations in soil, siderophore-binding protein receptors and commercialisation perspectives of siderophores. Besides, this review unearths the recent advancements in the characterisation of novel siderophores and its heavy metal complexes alongside the interaction kinetics with receptors. [ABSTRACT FROM AUTHOR]

The medicinal plants of the Asteraceae family are a valuable source of bioactive secondary metabolites, including polyphenols, phenolic acids, flavonoids, acetylenes, sesquiterpene lactones, triterpenes, etc. Under stressful conditions, the plants develop these secondary substances to carry out physiological tasks in plant cells. Secondary Asteraceae metabolites that are of the greatest interest to consumers are artemisinin (an anti-malarial drug from Artemisia annua L.—sweet wormwood), steviol glycosides (an intense sweetener from Stevia rebaudiana Bert.—stevia), caffeic acid derivatives (with a broad spectrum of biological activities synthesized from Echinacea purpurea (L.) Moench—echinacea and Cichorium intybus L.—chicory), helenalin and dihydrohelenalin (anti-inflammatory drug from Arnica montana L.—mountain arnica), parthenolide (“medieval aspirin” from Tanacetum parthenium (L.) Sch.Bip.—feverfew), and silymarin (liver-protective medicine from Silybum marianum (L.) Gaertn.—milk thistle). The necessity to enhance secondary metabolite synthesis has arisen due to the widespread use of these metabolites in numerous industrial sectors. Elicitation is an effective strategy to enhance the production of secondary metabolites in in vitro cultures. Suitable technological platforms for the production of phytochemicals are cell suspension, shoots, and hairy root cultures. Numerous reports describe an enhanced accumulation of desired metabolites after the application of various abiotic and biotic elicitors. Elicitors induce transcriptional changes in biosynthetic genes, leading to the metabolic reprogramming of secondary metabolism and clarifying the mechanism of the synthesis of bioactive compounds. This review summarizes biotechnological investigations concerning the biosynthesis of medicinally essential metabolites in plants of the Asteraceae family after various elicitor treatments.

Background: Bitter melon (Momordica charantia L.) is a widely cultivated food and medicinal plant native to the world's subtropics and tropics. Constraints affecting cultivation of Bitter melon affect productivity of β-carotene. Knowing the mechanism that controls the transcription of the β-carotene biosynthesis genes in Bitter melon will be of great value in improving the yield of this important metabolite. Methods and Results: The expressions of β-carotene biosynthetic genes such as Phytoene Desaturase (PDS) and Phytoene Synthase (PSY) were evaluated in Bitter melon accessions 'GBK027049', 'NS1026', 'Mahy-ventura', '453B' and 'Sibuka532'. Transcript expression level analysis of PSY and PDS, and amount of β-carotene in leaf, stem, and fruit, were determined using quantitative polymerase chain reaction and high-performance liquid chromatography (HPLC). Root transcript expression was used as a negative control for determining relative fold change in other tissues. Expression of PSY in fruit (6 to 27-fold compared to the control) was higher than in the other organs for all accessions. This was also the case of PDS expression (10 to 29-fold compared to the control). Leaves had the highest β-carotene concentration (17.92–45.35 µg∙g−1); there was no difference between stems (5.67–12.75 µg∙g−1) and fruit (6.18–12.53 µg∙g−1). The highest β-carotene content was in accessions 'GBK027049' (12.53–45.35 µg∙g−1) and '453B' (6.18–32.09 µg∙g−1). The PSY and PDS expressions were positively correlated with amount of β-carotene in leaves, stems, and fruits. Conclusion: Bitter melon leaves, especially those of 'GBK027049' and '453B' accessions, are an alternative to alleviate the β-carotene deficiencies in the world and especially in Africa. [ABSTRACT FROM AUTHOR]

Abstract Background Antibiotic resistance is on the rise, and new antibiotic research has slowed in recent years, necessitating the discovery of possibly novel microbial resources capable of producing bioactive compounds. Microbial infections are gaining resistance to existing antibiotics, emphasizing the need for novel medicinal molecules to be discovered as soon as possible. Because the possibilities of isolating undiscovered actinomycetes strains have decreased, the quest for novel products has shifted to rare actinomycetes genera from regular environments or the identification of new species identified in unusual habitats. Main body of the abstract The non-streptomyces actinobacteria are known as rare actinomycetes that are extremely difficult to cultivate. Rare actinomycetes are known to produce a variety of secondary metabolites with varying medicinal value. In this review, we reported the diversity of rare actinomycetes in several habitat including soil, plants, aquatic environment, caves, insects and extreme environments. We also reported some isolation methods to easily recover rare Actinobacteria from various sources guided with some procedures to identify the rare Actinobacteria isolates. Finally, we reported the biosynthetic potential of rare actinomycetes and its role in the production of unique secondary metabolites that could be used in medicine, agriculture, and industry. These microbial resources will be of interest to humanity, as antibiotics, insecticides, anticancer, antioxidants, to mention but a few. Short conclusion Rare actinomycetes are increasingly being investigated for new medicinal compounds that could help to address existing human health challenges such as newly emerging infectious illnesses, antibiotic resistance, and metabolic disorders. The bioactive secondary metabolites from uncommon actinomycetes are the subject of this review, which focuses on their diversity in different habitats, isolation, identification and biosynthetic potentials.

Multi-resistant bacterial pathogens are a major public health problem for treating nosocomial infections owing to their high resistance to antibiotics. The objective of this research was to characterize the bioactive molecules secreted by a novel moderately halophilic actinobacterium strain, designated GSB-11, exhibiting a strong antagonistic activity against several multidrug-resistant pathogenic bacteria. This potential strain was identified by phenotypic, genotypic (16S rRNA), and phylogenetic analyses. GSB-11 was related to “Streptomyces acrimycini” NBRC 12736 T with 99.59% similarity. Molecular screening by PCR assay demonstrated that the strain possesses two biosynthetic genes coding for NRPS and PKS-II. Two active compounds GSB11-6 and GSB11-7 were extracted from the cell-free culture supernatant of Bennett medium and purified using reversed-phase HPLC. According to spectrometric (mass spectrum) and spectroscopic (1H NMR, 13C NMR, 1H-1H COSY, and 1H-13C HMBC) spectra analyses, the compounds GSB11-6 and GSB11-7 were identified to be maculosin and N-acetyltyramine, respectively. Their minimum inhibitory concentrations (MIC) revealed interesting values against certain multidrug-resistant pathogenic bacteria. They were between 5 and 15 mg/mL for GSB11-6, 10 and 30 mg/mL for GSB11-7. To our best knowledge, this is the first study of these active substances isolated from “Streptomyces acrimycini” showing an interesting antibacterial activity. Therefore, these essential compounds could be candidates for future research against multidrug-resistant bacteria. [ABSTRACT FROM AUTHOR]

The complete genome sequence of the opportunistic pathogen Nocardia vulneris is reported. The strain N. vulneris LPB4002 was isolated from a clinical sample of a patient with actinomycetoma. The reported genome comprises a single 9,489-Kb closed chromosome, with 8,584 protein-coding genes and 68% GC content.

The discovery of new bioactive compounds is an invaluable aid to the development of new drugs. Strategies for finding novel molecules can focus on the exploitation of less studied organisms and ecosystems such as planctomycetes and brackish habitats. The unique cell biology of the underexplored Planctomycetota mean it is of particular interest. In this study, we aimed to isolate planctomycetes from the estuary of the Tejo river (Portugal). To reach this goal, macroalgae, water and sediments were sampled and diverse media and isolation techniques applied. Sixty-nine planctomycetal strains were brought into pure culture. An analysis of the 16S rRNA genes found that the majority of the isolates were affiliated to the genus Rhodopirellula. Putative novel taxa belonging to genera Stieleria and Rhodopirellula were also isolated and characterized morphologically. Enterobacterial repetitive intergenic consensus fingerprinting analyses showed higher diversity and different genotypes within close strains. Relevant biosynthetic gene clusters were found in most isolates and acetone extracts from representative strains exhibited mild antimicrobial activities against Escherichia coli and Staphylococcus aureus. Our work has not only enlarged the number and diversity of cultured planctomycetes but has also shown the potential for the discovery of bioactive compounds from the novel taxa. [ABSTRACT FROM AUTHOR]

Stevia rebaudiana (Bertoni) Bertoni is a plant of economic interest in the food and pharmaceutical industries due its steviol glycosides (SG), which are rich in metabolites that are 300 times sweeter than sucrose. In addition, S. rebaudiana plants contain phenolic compounds and flavonoids with antioxidant activity. Endophytic bacteria promote the growth and development and modulate the metabolism of the host plant. However, little is known regarding the role of endophytic bacteria in the growth; synthesis of SG, flavonoids and phenolic compounds; and the relationship between trichome development and specialized metabolites in S. rebaudiana, which was the subject of this study. The 12 bacteria tested did not increase the growth of S. rebaudiana plants; however, the content of SG increased with inoculation with the bacteria Enterobacter hormaechei H2A3 and E. hormaechei H5A2. The SG content in leaves paralleled an increase in the density of glandular, short, and large trichome. The image analysis of S. rebaudiana leaves showed the presence of SG, phenolic compounds, and flavonoids principally in glandular and short trichomes. The increase in the transcript levels of the KO, KAH, UGT74G1, and UGT76G1 genes was related to the SG concentration in plants of S. rebaudiana inoculated with E. hormaechei H2A3 and E. hormaechei H5A2. In conclusion, inoculation with the stimulating endophytes E. hormaechei H2A3 and E. hormaechei H5A2 increased SG synthesis, flavonoid content and flavonoid accumulation in the trichomes of S. rebaudiana plants. [ABSTRACT FROM AUTHOR]

The main objective of the study is the evaluation of the diversity of actinobacteria associated with Polytrichum strictum — dominant species of widespread Antarctic Тall moss turf subformation and their characteristics as the producers of biologically active compounds. The actinobacterial isolates were isolated by direct inoculation, phenol pretreatment, and heated treatment. The cultural properties of the isolates were evaluated using diagnostic media. The antimicrobial activity of the isolates was determined by the point inoculations method. The phylogenetic analysis was based on sequence analysis of the 16S rRNA gene. The biosynthetic genes screening was performed using polymerase chain reaction. A total of 23 actinobacterial isolates associated with P. strictum were isolated, the four identified genera being Streptomyces (7 isolates), Micromonospora (14 isolates), Kribbella (1 isolate), and Micrococcus (1 isolate). Eight psychrotrophic strains of all identified genera were identified. The optimal pH values for all isolates were in the range 6–10. Four isolates grew on the medium with 7.5% NaCl. A significant number of the isolates showed a wide range of enzymatic activities. Antagonists of a wide range of pathogenic microorganisms were found, including against multidrug-resistant strain of Candida albicans and Methicillin-resistant Staphylococcus aureus. Some strains were active against phytopathogenic bacteria, namely three strains against Erwinia amylovora, one strain against Agrobacterium tumefaciens, and one strain against Pectobacterium carotovorum. More than half of the isolates showed antifungal activity against Fusarium oxysporum and Aspergillus niger. The biosynthetic genes involved in synthesizing a wide range of bioactive compounds were found in more than 80% of isolates. Antarctic actinobacteria isolated in this study demonstrate potential as the producers of a wide range of biologically active compounds. Further studies of these actinobacteria may lead to the identification of previously unknown biologically active compounds.

ABSTRACT Natural products of lichen-forming fungi are structurally diverse and have a variety of medicinal properties. Despite this, they have limited implementation in industry mostly because the corresponding genes are unknown for most of their natural products. Here, we implement a long-read sequencing and bioinformatic approach to identify the putative biosynthetic gene cluster of the bioactive natural product gyrophoric acid (GA). Using 15 high-quality genomes representing nine GA-producing species of the lichen-forming fungal genus Umbilicaria, we identify the most likely GA cluster and investigate the cluster gene organization and composition across the nine species. Our results show that GA clusters are promiscuous within Umbilicaria, and only three genes are conserved across species, including the polyketide synthase (PKS) gene. In addition, our results suggest that the same cluster codes for different, but structurally similar compounds, namely, GA, umbilicaric-, and hiascic acid, bringing new evidence that lichen metabolite diversity is also generated through regulatory mechanisms at the molecular level. Ours is the first study to identify the most likely GA cluster and, thus, provides essential information to open new avenues for biotechnological approaches to producing and modifying GA and similar lichen-derived compounds. GA PKS is the first tridepside PKS to be identified. IMPORTANCE The implementation of natural products in the pharmaceutical industry relies on the possibility of modifying the natural product (NP) pathway to optimize yields and pharmacological effects. Characterization of genes and pathways underlying natural product biosynthesis is a major bottleneck for exploiting the medicinal properties of the natural products. Genome mining is a promising and relatively cost- and time-effective approach to utilize unexplored NP resources for drug discovery. In this study, we identify the most likely gene cluster for the lichen-forming fungal depside gyrophoric acid in nine Umbilicaria species. This compound shows cytotoxic and antiproliferative properties against several cancer cell lines and is also a broad-spectrum antimicrobial agent. This information paves the way for generating GA analogs with modified properties by selective activation/deactivation of genes.

Stevia rebaudiana (Bertoni) Bertoni is a plant of economic interest in the food and pharmaceutical industries due its steviol glycosides (SG), which are rich in metabolites that are 300 times sweeter than sucrose. In addition, S. rebaudiana plants contain phenolic compounds and flavonoids with antioxidant activity. Endophytic bacteria promote the growth and development and modulate the metabolism of the host plant. However, little is known regarding the role of endophytic bacteria in the growth; synthesis of SG, flavonoids and phenolic compounds; and the relationship between trichome development and specialized metabolites in S. rebaudiana, which was the subject of this study. The 12 bacteria tested did not increase the growth of S. rebaudiana plants; however, the content of SG increased with inoculation with the bacteria Enterobacter hormaechei H2A3 and E. hormaechei H5A2. The SG content in leaves paralleled an increase in the density of glandular, short, and large trichome. The image analysis of S. rebaudiana leaves showed the presence of SG, phenolic compounds, and flavonoids principally in glandular and short trichomes. The increase in the transcript levels of the KO, KAH, UGT74G1, and UGT76G1 genes was related to the SG concentration in plants of S. rebaudiana inoculated with E. hormaechei H2A3 and E. hormaechei H5A2. In conclusion, inoculation with the stimulating endophytes E. hormaechei H2A3 and E. hormaechei H5A2 increased SG synthesis, flavonoid content and flavonoid accumulation in the trichomes of S. rebaudiana plants.

Tectona grandis L.f. is a tropical hardwood tree which is known for its timber yield. Apart from its durable wood, the leaves of teak are rich source of anthocyanin. The main objective of the present study was to analyze the expression profile of major anthocyanin biosynthetic genes from the young and mature leaves of teak. The young leaves of teak contains significant amount of anthocyanin when compared to mature leaves. The key enzyme in the anthocyanin biosynthetic pathway, PAL, the regulatory enzyme, CHI and the end point enzyme UGT showed sound activity in young leaves. The obtained results were further correlated by the higher expression profile of major anthocyanin biosynthetic genes such as CHS1, CHS2, CHI1, CHI2, F3'5'H1, F3'5'H2, DFR, ANS and UF3GTin the young leaves. [ABSTRACT FROM AUTHOR]

Herbaceous peony (Paeonia lactiflora Pall.) is an ornamental plant with huge potential in the international flower market. Similar to the flowers of most other ornamental plants, the top sellers of P. lactiflora are those with red or pink flowers. However, most studies on flower colors have focused on the novel colors and have neglected the most common red flowers. In this study, a red cultivar of P. lactiflora ('Dafugui') and a pink cultivar ('Qingwen') were selected in order to study the discrepancy in the red color of the flowers. The results demonstrate that these two cultivars have the same compositions as anthocyanins, flavones, and flavonols but different contents. 'Dafugui' was found to have a high accumulation of upstream substances due to the higher expression of the early genes encoding phenylalanine ammonialyase (PlPAL) and flavonoid 3′-hydroxylase (PlF3′H). Moreover, the anthocyanidin synthase gene (PlANS) and UDP-glucose flavonoid 3-O-glucosyltransferase gene (PlUF3GT) encoding enzymes catalyze these upstream substances into anthocyanins, resulting in more redness in 'Dafugui' than in 'Qingwen'. Our study thus provides a better understanding of the anthocyanin accumulation and coloring mechanism of P. lactiflora and can serve as a theoretical basis for breeding more red flowers using genetic engineering techniques to cater to consumers' preferences. [ABSTRACT FROM AUTHOR]

Pukzing cave, the largest cave of Mizoram, India was explored for bacterial diversity. Culture dependent method revealed 235 bacterial isolates using three different treatments. Identity of the microbial species was confirmed by 16S rDNA sequencing. The highest bacterial population was recovered from heat treatment (n = 97;41.2%) followed by normal (n = 79;33.6%) and cold treatment (n = 59;25.1%) indicating dominance of moderate thermophiles. Antimicrobial potential of isolates showed 20.4% isolates having antimicrobial ability against tested pathogens. Amplicon sequencing of PKSI, PKSII and NRP specific genes revealed presence of AMP genes in the microbial population. Six microbial pathogens were selected for screening as they are well known for different disease cause organism in various fields such as agriculture and human health. Cave environment harbors unique microbial flora and hypervariable region V4 is more informative. Higher activity of AMP assay against these microbes indicates that cave microbial communities could be potential source of future genomic resources. • Study revealed Pukzing cave ecosystem as a unique source of endemic and moderate thermophilic microorganisms. • Amplicon sequencing of PKSI, PKSII and NRP specific genes revealed presence of AMP genes in the microbial population. • Cave environment harbours unique microbial flora and hypervariable region V4 was found to be more informative. • The study concludes that cave microbial communities could be potential source of future genomic resources. [ABSTRACT FROM AUTHOR]

Fungal contamination of agricultural commodities, particularly by mycotoxigenic fungi, represents an enormous concern for global food security in terms of feeding the world's growing population with sufficient and safe food. Not only do they reduce crop yield and quality, but they also produce substantial numbers of mycotoxins, which pose serious adverse health effects in human and animals. As the genome of most mycotoxigenic species have been sequenced, the gene clusters involved in the biosynthesis of agriculturally important mycotoxins including aflatoxins, fumonisins, ochratoxins, zearalenone and trichothecenes, have been largely identified and characterised, with their roles elucidated by researchers. This review provides a comprehensive overview of the current knowledge of genes involved in the biosynthetic pathways of mycotoxins. In addition, the influence of climatic factors including water, temperature and carbon dioxide on differential mycotoxin gene expressions have been highlighted. Overall, the relationship between the relative expression of key regulatory and structural genes under different environmental conditions is significantly correlated with mycotoxins production. This indicates that mycotoxin gene induction can be used as a reliable indicator or marker to monitor mycotoxin production pre-and-post harvest. Furthermore, current strategies to manage mycotoxin risks still require improvement. Thus, an accurate understanding of the molecular mechanisms of mycotoxin biosynthesis in mycotoxigenic species could help to develop an innovative, robust targeted control strategy. This could include the exploitation of novel compounds, which can inhibit biosynthetic genes, to minimise mycotoxin risks. [ABSTRACT FROM AUTHOR]

Glucosinolates (GSLs) are important secondary metabolites in Brassicales related to insect and disease resistance, flavor formation, and human health. Here, we determined the GSL profile with sinigrin as the predominant GSL in Brassica nigra. A total of 184 GSL biosynthetic genes (BniGSLs) were identified in B. nigra by a genome-wide search for orthologs of 82 of the 95 known GSL genes in Arabidopsis thaliana. Transcriptome data demonstrated that at least one BniGSL was highly expressed in stems and leaves at each step of the sinigrin synthesis pathway, which ensured the synthesis of a large amount of sinigrin in B. nigra. Among these key candidates of BniGSLs, the high expression of BniMAM1-2, BniCYP79F1, and BniAOP2-1/2, and the absence of MAM3 and AOP3, may contribute remarkably to the synthesis and accumulation of sinigrin. In addition, the low expression of some key BniGSLs partially explains the low content of indolic and aromatic GSLs in B. nigra. This study provided a genetic explanation for the formation of the unique GSL profile with sinigrin as the main GSL in B. nigra. The results of this study will be valuable for further functional analysis of BniGSLs and genetic improvement of GSLs in B. nigra and other Brassica species. [ABSTRACT FROM AUTHOR]

Herbaceous peony (Paeonia lactiflora Pall.) is an ornamental plant with huge potential in the international flower market. Similar to the flowers of most other ornamental plants, the top sellers of P. lactiflora are those with red or pink flowers. However, most studies on flower colors have focused on the novel colors and have neglected the most common red flowers. In this study, a red cultivar of P. lactiflora (‘Dafugui’) and a pink cultivar (‘Qingwen’) were selected in order to study the discrepancy in the red color of the flowers. The results demonstrate that these two cultivars have the same compositions as anthocyanins, flavones, and flavonols but different contents. ‘Dafugui’ was found to have a high accumulation of upstream substances due to the higher expression of the early genes encoding phenylalanine ammonialyase (PlPAL) and flavonoid 3′-hydroxylase (PlF3′H). Moreover, the anthocyanidin synthase gene (PlANS) and UDP-glucose flavonoid 3-O-glucosyltransferase gene (PlUF3GT) encoding enzymes catalyze these upstream substances into anthocyanins, resulting in more redness in ‘Dafugui’ than in ‘Qingwen’. Our study thus provides a better understanding of the anthocyanin accumulation and coloring mechanism of P. lactiflora and can serve as a theoretical basis for breeding more red flowers using genetic engineering techniques to cater to consumers’ preferences.

Little is known on the impact that climate change (CC) may have on Aspergillus carbonarius and Ochratoxin A (OTA) contamination of grapes, especially in the Mediterranean region where in CC scenarios temperature are expected to increase by +2–5 °C and CO 2 from 400 to 800/1200 ppm. This study examined the effect of (i) current and increased temperature in the alternating 11.5 h dark/12.5 h light cycle (15–28 °C vs 18–34 °C), representative of the North Apulia area, South Italy and (ii) existing and predicted CO 2 concentrations (400 vs 1000 ppm), on growth, expression of biosynthetic genes (AcOTApks , AcOTAnrps , AcOTAhal , AcOTAp450 , AcOTAbZIP) and regulatory genes of Velvet complex (laeA / veA / velB , "velvet complex") involved in OTA biosynthesis and OTA phenotypic production by three strains of A. carbonarius. The experiments made on a grape-based matrix showed that elevated CO 2 resulted in a general stimulation of growth and OTA production. These results were also supported by the up-regulation of both structural and regulatory genes involved in the OTA biosynthesis. Our work has shown for the first time that elevated CO 2 concentration in the Mediterranean region may result in an increased risk of OTA contamination in the wine production chain. • Influence of alternate T° and increase of CO 2 on ecophysiology of A spergillus carbonarius. • In vitro simulation of a climate change scenario in Apulia region. • Respect to other aspergilli, A. carbonarius grown faster under increased CO 2. • Relative expression of structural and regulatory genes paralleled OTA production. • Increased ochratoxigenic risk in grapes under higher CO 2 concentration. [ABSTRACT FROM AUTHOR]

We explored the relationship between skin color and the expression of genes related to carotenoid biosynthesis during fruit ripening in two citrus cultivars, 'Shiranuhi' (a hybrid mandarin cultivar) and 'Suneat' (mutant cultivar derived from a natural bud mutation of 'Shiranuhi'). We identified 16 and 7 genes putatively involved in carotenoid biosynthesis and regulation via phylogenetic analysis in sweet orange. Further, we determined the expression pattern of these genes by quantitative real time reverse transcriptase PCR (qRT-PCR). The result showed that the expression levels of CsPSY (Cs6g15910), CsZDS (Cs3g11180), CsZ-ISO (Cs5g24730), CsBCH1 (Cs9g19270), CsFUL2 (Cs5g12280), CsTAGL1 (Cs7g16960), CsRIN1 (Cs6g19680), CsRIN2 (Cs7g10980), and CsHY5 (Cs7g05140) were up-regulated in the skin of mutant cultivar 'Suneat' than any other tissues of both citrus cultivars. Of these CsPSY, CsZDS, CsZ-ISO and CsBCH1 genes were related to carotenoid biosynthesis and CsFUL2, CsTAGL1, CsRIN1, CsRIN2, and CsHY5 were known to involve in the regulation of carotenoid biosynthesis. Our results reveal that the attractive dark orange skin color of 'Suneat' might be due to the up-regulation of carotenoid biosynthetic as well as regulatory genes and thereby higher levels carotenoids at ripening. [ABSTRACT FROM AUTHOR]

Penicillium verrucosum contaminates temperate cereals with ochratoxin A (OTA) during harvesting and storage. We examined the effect of temperature (25 vs 30 oC), CO 2 (400 vs 1000 ppm) and matric/solute stress (-2.8 vs -7.0 MPa) on (i) growth, (ii) key OTA biosynthetic genes and (iii) OTA production on a milled wheat substrate. Growth was generally faster under matric than solute stress at 25 oC, regardless of CO 2 concentrations. At 30 oC, growth of P. verrucosum was significantly reduced under solute stress in both CO 2 treatments, with no growth observed at -2.8 MPa (=0.98 water activity, a w) and 1000 ppm CO 2. Overall, growth patterns under solute stress was slower in elevated CO 2 than under matric stress when compared with existing conditions. The otapks PV gene expression was increased under elevated CO 2 levels in matric stress treatments. There was fewer effects on the otanrps PV biosynthetic gene. This pattern was paralleled with the production of OTA under these conditions. This suggest that P. verrucosum is able to actively grow and survive in both soil and on crop debris under three way interacting climate-related abiotic factors. This resilience suggests that they would still be able to pose an OTA contamination risk in temperate cereals post-harvest. • Growth of Penicillium verrucosum was more sensitive to non-ionic solute than matric stress. • Exposure to climate-related interacting abiotic factors affected growth. • The otapks PV gene expression increased under elevated CO 2 levels in matric stress. • There was less effect on th e otanrps PV biosynthetic gene. • Ochratoxin A production was increased under matric stress at 30 °C and elevated CO 2. [ABSTRACT FROM AUTHOR]

Introduction: The white-spotted flower chafer ( Protaetia brevitarsis seulensis ), which is widely distributed in Asian countries, is traditionally used in oriental medicine. However, its larvae are prone to severe damage by green muscardine disease (caused by Metarhizium anisopliae ) during breeding. The aim of this study was to characterize Bacillus velezensis TJS119, which has been isolated from freshwater, and investigate its potential as a biocontrol agent against M. anisopliae in insects., Methods: TJS119 was obtained from freshwater samples in the Republic of Korea and was classified as B. velezensis . We evaluated its in vitro antifungal effect, sequenced the bacterial whole genome, mined genes responsible for the synthesis of secondary metabolites, performed secondary metabolite analysis Ultra performance liquid chromatography-mass spectrometry (UPLC-MS/MS), and conducted bioassays for determining green muscardine disease control ability., Results: Bacillus velezensis TJS119 inhibited the mycelial growth of M . anisopliae in vitro . The size of the B. velezensis TJS119 genome was estimated to be 3,890,913 bp with a GC content of 46.67% and 3,750 coding sequences. Biosynthetic gene clusters for secondary metabolites with antifungal activity were identified in the genome. Lipopeptides, including fengycin secreted by TJS119 exhibit antifungal activity. Application of TJS119 for the biocontrol against green muscardine disease increased the viability of white-spotted flower chafer by 94.7% compared to the control., Discussion: These results indicate that B. velezensis TJS119 is a potential biocontrol agent for insect pathogens., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Han, Nam, Hwang, Kim, Jung, Kim and Lee.)

8-Azaguanine (1) is a special 1,2,3-triazole containing natural product that possesses potent antibacterial and antitumor activities. In the present study, the entire 8-azaguanine biosynthetic gene cluster was located from Streptomyces CGMCC4.1633. Targeted gene disruption, heterologous expression analysis, and feeding experiments identified crucial genes for 8-azaguanine production. Moreover, we characterized the structure of two novel metabolites, analyzed NO (or reactive nitrogen species) related genes 8-azgA/B and radical SAM enzyme homologous 8-AzgG, and verified the non-enzymatic ring formation reaction of 8-azaguanine 1,2,3-triazole. All of the data and presumptions provide insight into the timing and mechanism of the enzymatic and non-enzymatic pathway that produce 8-azaguanine-type 1,2,3-triazole.

A new strain of Bacillus subtilis isolated from deep-sea core sediment sample (1400 m depth) produced antimicrobial peptides (AMPs) when cultured at 50 and 100 bar pressure conditions. The minimum inhibitory concentrations (MIC) showed that the AMPs had potent activity against V. cholerae and K. pneumoniae. AMPs extracted from cells grown at ambient and elevated pressure conditions exhibited distinct antifungal and antibacterial activities. Analysis of genes encoding AMPs revealed the presence of srfAA, sbo and bmyB biosynthetic genes. GC-MS analysis confirmed substantial accumulation of unsaturated fatty acids in membrane lipids of the cells in response to elevated pressure. [ABSTRACT FROM AUTHOR]

Curvulamine, a novel scaffold alkaloid with remarkable selective antibacterial activity, is produced by marine fungus Curvularia sp. IFB-Z10. However, its deep pharmaceutical research and application are severely restricted by the low yield, which needs to be solved urgently. The purpose of this study was to improve curvulamine production via precursors co-addition strategy and further reveal the regulation mechanism. In this work, the optimal precursors co-addition conditions were firstly obtained, and curvulamine production achieved 166.74 mg/L with the supply of 250 mg/L alanine and 200 mg/L proline at 60 h, which was 4.08 times that of control. It was observed that under alanine and proline stimulation, fungus exhibited the morphology of a small-diameter compact pellet. Furthermore, the organic acid levels in central carbon metabolism (CCM) were declined with precursors supplement. Besides, precursors also induced the critical biosynthetic gene transcriptions. The above findings collectively promoted curvulamine synthesis. Finally, Curvularia sp. IFB-Z10 fermentation process was successfully established by feeding alanine and proline at 0.021 g/L/h and 0.017 g/L/h rate from 60 to 72 h, and curvulamine production reached 133.58 mg/L in a 5-L bioreactor. The information acquired would facilitate the enhancement of curvulamine yield in submerged fermentation and the research on synthesis regulation of other alkaloids. [ABSTRACT FROM AUTHOR]

Actinobacteria are important producers of bioactive compounds. Extreme ecosystems cause evolution of novel secondary metabolic pathways of Actinobacteria and increase the possible discovery of new biological functions of bioactive compounds. Here, we isolated 65 Actinobacteria from rhizosphere soil samples of Opuntia stricta. An Actinobacteria strain (named SCA3-4) was screened against Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4, ATCC 76255). The strain produced pink–white aerial mycelia and brown substrate mycelium on Gause No. 1 agar. Biverticillate chains of cylindrical spores were observed by scanning electron microscopy (SEM). Based on alignment of 16S rRNA sequences, a constructed phylogenetic tree showed that strain SCA3-4 shared a 99.54% similarity with Streptomyces lilacinus NRRL B-1968T. The morphological, biochemical, physiological, and molecular characteristics further indicated that strain SCA3-4 belongs to the Streptomyces sp. It can grow well on medium with the following antibiotics chloramphenicol, streptomycin, penicillin-G, gentamicin, erythromycin, nystatin or neomycin sulfate. The polymerase chain reaction (PCR) amplification of types I and II polyketide synthase genes (PKS-I and PKS-II) suggested its bioactive potential. Under treatment with 100 μg/ml of ethyl acetate extracts isolated from Streptomyces sp. SCA3-4, growth of Foc TR4 was inhibited and cell membrane was destroyed. Crude extracts also showed a broad-spectrum antifungal activity against 13 phytopathogenic fungi including Foc TR4 and displayed the lowest minimum inhibitory concentration (MIC) (0.781 μg/ml) against Colletotrichum fragariae (ATCC 58718). A total of 21 different compounds identified by gas chromatography–mass spectrometry (GC-MS) were composed of phenolic compound, pyrrolizidine, hydrocarbons, esters, and acids. Besides the known active compounds, Streptomyces sp. SCA3-4 possesses antimicrobial or other biological activities. Further attention will be paid on other compounds with no functional annotation, aiming at the discovery of new bioactive substances.

• The positive effect of CaCl 2 addition on curvulamine production was firstly studied. • Intracellular Ca2+ controlled fungus morphology to promote curvulamine formation. • Intracellular Ca2+ up-regulated transcriptions and expressions of key biosynthetic genes to improve curvulamine biosynthesis. • CaCl 2 addition strategy was successfully established in 5-L scale fermentation. Curvulamine is a novel framework alkaloid with prominent antibacterial and acetylcholinesterase inhibitory activities produced by marine fungus, Curvularia sp. IFB-Z10. However, the low yield severely restricts its further pharmaceutical researches and applications. The study was aimed to enhance curvulamine production based on CaCl 2 addition strategy and further clarify the underlying regulation mechanism of Ca2+. In this work, the optimal addition conditions of CaCl 2 were firstly obtained, and curvulamine production achieved 42.96 mg/L under supplying 5 mM CaCl 2 at 0 h, which was 3.33-fold that of control in shake flask. It was further found that cytosolic Ca2+ level was markedly increased through calcium channel under CaCl 2 stimulation. Relatively high intracellular Ca2+ level could induce fungus to principally form pellets with small diameter and compact structure (morphology), and significantly up-regulate the transcriptional and expression levels of key biosynthetic genes, which collectively promoted curvulamine synthesis. Finally, CaCl 2 addition strategy was successfully applied in 5-L bioreactor. This work provided an effective regulation strategy to improve curvulamine production in submerged fermentation of Curvularia sp. and it would facilitate further research on the synthesis regulation of secondary metabolites from other marine filamentous fungi. [ABSTRACT FROM AUTHOR]

This study examined the effect of climate change (CC) abiotic factors of temperature (20, 25, 30 °C), water activity (a w ; 0.995, 0.98) and CO 2 exposure (400, 1000 ppm) may have on (a) growth, (b) gene expression of biosynthetic toxin genes (Tri5, Tri6, Tri16), and (c) T-2/HT-2 toxins and associated metabolites by Fusarium langsethiae on oat-based media and in stored oats. Lag phases and growth were optimum at 25 °C with freely available water. This was significantly reduced at 30 °C, at 0.98 a w and 1000 ppm CO 2 exposure. In oat-based media and stored oats, Tri5 gene expression was reduced in all conditions except 30 °C, 0.98 a w , elevated CO 2 where there was a significant (5.3-fold) increase. The Tri6 and Tri16 genes were upregulated, especially in elevated CO 2 conditions. Toxin production was higher at 25 °C than 30 °C. In stored oats, at 0.98 a w , elevated CO 2 led to a significant increase (73-fold) increase in T2/HT-2 toxin, especially at 30 °C. Nine T-2 and HT-2 related metabolites were detected, including a new dehydro T-2 toxin (which correlated with T-2 production) and the conjugate, HT-2 toxin, glucuronide. This shows that CC factors may have a significant impact on growth and mycotoxin production by F. langsethiae. [ABSTRACT FROM AUTHOR]

Actinobacteria are important producers of bioactive compounds. Extreme ecosystems cause evolution of novel secondary metabolic pathways of Actinobacteria and increase the possible discovery of new biological functions of bioactive compounds. Here, we isolated 65 Actinobacteria from rhizosphere soil samples of Opuntia stricta. An Actinobacteria strain (named SCA3-4) was screened against Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4, ATCC 76255). The strain produced pink–white aerial mycelia and brown substrate mycelium on Gause No. 1 agar. Biverticillate chains of cylindrical spores were observed by scanning electron microscopy (SEM). Based on alignment of 16 S rRNA sequences, a constructed phylogenetic tree showed that strain SCA3-4 shared a 99.54% similarity with Streptomyces lilacinus NRRL B-1968T. The morphological, biochemical, physiological, and molecular characteristics further indicated that strain SCA3-4 belongs to the Streptomyces sp. It can grow well on medium with the following antibiotics chloramphenicol, streptomycin, penicillin-G, gentamicin, erythromycin, nystatin or neomycin sulfate. The polymerase chain reaction (PCR) amplification of types I and II polyketide synthase genes (PKS-I and PKS-II) suggested its bioactive potential. Under treatment with 100 μg/ml of ethyl acetate extracts isolated from Streptomyces sp. SCA3-4, growth of Foc TR4 was inhibited and cell membrane was destroyed. Crude extracts also showed a broad-spectrum antifungal activity against 13 phytopathogenic fungi including Foc TR4 and displayed the lowest minimum inhibitory concentration (MIC) (0.781 μg/ml) against Colletotrichum fragariae (ATCC 58718). A total of 21 different compounds identified by gas chromatography–mass spectrometry (GC-MS) were composed of phenolic compound, pyrrolizidine, hydrocarbons, esters, and acids. Besides the known active compounds, Streptomyces sp. SCA3-4 possesses antimicrobial or other biological activities. Further attention will be paid on other compounds with no functional annotation, aiming at the discovery of new bioactive substances. [ABSTRACT FROM AUTHOR]

Bacterial natural products (NPs) are still a major source of new drug leads. Polyketides (PKs) and non-ribosomal peptides (NRP) are two pharmaceutically important families of NPs and recent studies have revealed Antarctica to harbor endemic polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes, likely to be involved in the production of novel metabolites. Despite this, the diversity of secondary metabolites genes in Antarctica is still poorly explored. In this study, a computational bioprospection approach was employed to study the diversity and identity of PKS and NRPS genes to one of the most biodiverse areas in maritime Antarctica—Maxwell Bay. Amplicon sequencing of soil samples targeting ketosynthase (KS) and adenylation (AD) domains of PKS and NRPS genes, respectively, revealed abundant and unexplored chemical diversity in this peninsula. About 20% of AD domain sequences were only distantly related to characterized biosynthetic genes. Several PKS and NRPS genes were found to be closely associated to recently described metabolites including those from uncultured and candidate phyla. The combination of new approaches in computational biology and new culture-dependent and -independent strategies is thus critical for the recovery of the potential novel chemistry encoded in Antarctica microorganisms.

An actinomycete strain, CB-75, was isolated from the soil of a diseased banana plantation in Hainan, China. Based on phenotypic and molecular characteristics, and 99.93% sequence similarity with Streptomyces spectabilis NBRC 13424 (AB184393), the strain was identified as Streptomyces sp. This strain exhibited broad-spectrum antifungal activity against 11 plant pathogenic fungi. Type I polyketide synthase (PKS-I) and non-ribosomal peptide synthetase (NRPS) were detected, which were indicative of the antifungal compounds that Streptomyces sp. CB-75 could produce. An ethyl acetate extract from the strain exhibited the lowest minimum inhibitory concentration (MIC) against Colletotrichum musae (ATCC 96167) (0.78 μg/ml) and yielded the highest antifungal activity against Colletotrichum gloeosporioides (ATCC 16330) (50.0 μg/ml). Also, spore germination was significantly inhibited by the crude extract. After treatment with the crude extract of Streptomyces sp. CB-75 at the concentration 2 × MIC, the pathogenic fungi showed deformation, shrinkage, collapse, and tortuosity when observed by scanning electron microscopy (SEM). By gas chromatography-mass spectrometry (GC-MS) of the crude extract, 18 chemical constituents were identified; (Z)-13-docosenamide was the major constituent. Pot experiments showed that the incidence of banana seedlings was reduced after using Streptomyces sp. CB-75 treatment. The disease index was 10.23, and the prevention and control effect was 83.12%. Furthermore, Streptomyces sp. CB-75 had a growth-promoting effect on banana plants. The chlorophyll content showed 88.24% improvement, the leaf area, root length, root diameter, plant height, and stem showed 88.24, 90.49, 136.17, 61.78, and 50.98% improvement, respectively, and the shoot fresh weight, root fresh weight, shoot dry weight, and root dry weight showed 82.38, 72.01, 195.33, and 113.33% improvement, respectively, compared with treatment of fermentation broth without Streptomyces sp. CB-75. Thus, Streptomyces sp. CB-75 is an important microbial resource as a biological control against plant pathogenic fungi and for promoting banana growth.

Glucosinolates are anti-carcinogenic, anti-oxidative biochemical compounds that defend plants from insect and microbial attack. Glucosinolates are abundant in all cruciferous crops, including all vegetable and oilseed Brassica species. Here, we studied the expression of glucosinolate biosynthesis genes and determined glucosinolate contents in the edible organs of a total of 12 genotypes of Brassica oleracea: three genotypes each from cabbage, kale, kohlrabi and cauliflower subspecies. Among the 81 genes analyzed by RT-PCR, 19 are transcription factor-related, two different sets of 25 genes are involved in aliphatic and indolic biosynthesis pathways and the rest are breakdown-related. The expression of glucosinolate-related genes in the stems of kohlrabi was remarkably different compared to leaves of cabbage and kale and florets of cauliflower as only eight genes out of 81 were expressed in the stem tissues of kohlrabi. In the stem tissue of kohlrabi, only one aliphatic transcription factor-related gene, Bol036286 (MYB28) and one indolic transcription factor-related gene, Bol030761 (MYB51), were expressed. The results indicated the expression of all genes is not essential for glucosinolate biosynthesis. Using HPLC analysis, a total of 16 different types of glucosinolates were identified in four subspecies, nine of them were aliphatic, four of them were indolic and one was aromatic. Cauliflower florets measured the highest number of 14 glucosinolates. Among the aliphatic glucosinolates, only gluconapin was found in the florets of cauliflower. Glucoiberverin and glucobrassicanapin contents were the highest in the stems of kohlrabi. The indolic methoxyglucobrassicin and aromatic gluconasturtiin accounted for the highest content in the florets of cauliflower. A further detailed investigation and analyses is required to discern the precise roles of each of the genes for aliphatic and indolic glucosinolate biosynthesis in the edible organs.

Ethylene is involved in regulation of various aspects of plant growth and development. Physiological and genetic analyses have indicated the existence of crosstalk between ethylene and other phytohormones, including auxin, cytokinin (CK), abscisic acid (ABA), gibberellin (GA), salicylic acid (SA), jasmonic acid (JA), brassinosteroid (BR) and strigolactone (SL) in regulation of different developmental processes. However, the effects of ethylene on the biosynthesis and contents of these hormones are not fully understood. Here, we investigated how overproduction of ethylene may affect the contents of other plant hormones using the ethylene-overproducing mutant ethylene-overproducer 1 ( eto1-1 ). The contents of various hormones and transcript levels of the associated biosynthetic genes in the 10-day-old Arabidopsis eto1-1 mutant and wild-type (WT) plants were determined and compared. Higher levels of CK and ABA, while lower levels of auxin, SA and GA were observed in eto1-1 plants in comparison with WT, which was supported by the up- or down-regulation of their biosynthetic genes. Although we could not quantify the BR and SL contents in Arabidopsis , we observed that the transcript levels of the potential rate-limiting BR and SL biosynthetic genes were increased in the eto1-1 versus WT plants, suggesting that BR and SL levels might be enhanced by ethylene overproduction. JA level was not affected by overproduction of ethylene, which might be explained by unaltered expression level of the proposed rate-limiting JA biosynthetic gene allene oxide synthase . Taken together, our results suggest that ET affects the levels of auxin, CK, ABA, SA and GA, and potentially BR and SL, by influencing the expression of genes involved in the rate-limiting steps of their biosynthesis. [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum L.) is one of the most important and popular vegetables worldwide. A wide range of tomato cultivars with different colored fruits is presently available. The purple peel of tomato fruit is due to the accumulation anthocyanin pigments, which are beneficial to both plants and humans. Cultivated tomatoes normally do not make anthocyanin in their fruit peel, but there are some wild relatives of cultivated tomato like Solanum chilense, S. habrochaites, S. cheesmanii, and S. lycopersicoides that do produce anthocyanins in their fruits. In this study, the purple fruit color was obtained by crossing ‘OSU blue’ (blue fruit) and ‘Purple mini’ (brown fruit) and subsequent self-pollination. Anthocyanins are produced via the flavonoid pathway and are regulated by the transcriptional complex of MYB, bHLH, and WD40 repeats transcription factors. We determined the expression profiles of genes related to anthocyanin biosynthesis in tomato genotypes with distinct fruit colors by qRT-PCR. Both the early and late biosynthetic genes of the anthocyanin pathway were up-regulated in the peels of purple tomato fruits, except Sl5GT. Moreover, the expression of the regulatory genes SlANT1 and SlAN1 was dramatically increased in the peels of purple tomato fruits. These results indicate that SlANT1 and SlAN1 might play an important role on anthocyanin biosynthesis in the peels of purple-fruited tomatoes via up-regulation of structural genes in the anthocyanin pathway. [ABSTRACT FROM AUTHOR]

Kohlrabi (Brassica oleracea var. gongylodes L.) is an important vegetable of the Brassicaceae family. The main edible part of kohlrabi is the swollen stem. The purple cultivars make anthocyanin mainly in the peel of the swollen stem, while in the leaf, it is limited to the midrib, but green cultivars do not. Anthocyanins are advantageous for both plants as well as humans. Two anthocyanin compounds were detected by high pressure liquid chromatography (HPLC) only in the peel of the purple kohlrabi cultivar. Three MYBs, three bHLHs, and one WD40 TF were identified as the candidate regulatory genes in kohlrabi. There was an abundance of transcript levels for the late biosynthetic genes more specifically for BoF3′H, BoDFR, BoLDOX, and BoGST in the purple peel while scarcely detectable in other tissues for both cultivars. The expression of BoPAP2 and BoTT8 was higher in the peel of the purple cultivar than the green cultivar. The expression of BoMYBL2.2 orthologue of Arabidopsis MYBL2, a negative regulator of anthocyanins, was dramatically decreased in the purple peel. The expression of BoACO1, a key gene for ethylene biosynthesis, and BoNCED3, an important gene of the ABA pathway, was down- and upregulated, respectively, in the peel of purple kohlrabi. [ABSTRACT FROM AUTHOR]

Anthocyanins are the resultant end-point metabolites of phenylapropanoid/flavonoid (F/P) pathway which is regulated at transcriptional level via a series of structural genes. Identifying the key genes and their potential interactions can provide us with the clue for novel points of intervention for improvement of the trait in strawberry. We profiled the expressions of putative regulatory and biosynthetic genes of cultivated strawberry in three developmental and characteristically colored stages of fruits of contrastingly anthocyanin rich cultivars: Tokun, Maehyang and Soelhyang. Besides FaMYB10, a well-characterized positive regulator, FaMYB5, FabHLH3 and FabHLH3-delta might also act as potential positive regulators, while FaMYB11, FaMYB9, FabHLH33 and FaWD44-1 as potential negative regulators of anthocyanin biosynthesis in these high-anthocyanin cultivars. Among the early BGs, Fa4CL7, FaF3H, FaCHI1, FaCHI3, and FaCHS, and among the late BGs, FaDFR4-3, FaLDOX, and FaUFGT2 showed significantly higher expression in ripe fruits of high anthocyanin cultivars Maehyang and Soelhyang. Multivariate analysis revealed the association of these genes with total anthocyanins. Increasingly higher expressions of the key genes along the pathway indicates the progressive intensification of pathway flux leading to final higher accumulation of anthocyanins. Identification of these key genetic determinants of anthocyanin regulation and biosynthesis in Korean cultivars will be helpful in designing crop improvement programs. [ABSTRACT FROM AUTHOR]

An actinomycete strain, CB-75, was isolated from the soil of a diseased banana plantation in Hainan, China. Based on phenotypic and molecular characteristics, and 99.93% sequence similarity with Streptomyces spectabilis NBRC 13424 (AB184393), the strain was identified as Streptomyces sp. This strain exhibited broad-spectrum antifungal activity against 11 plant pathogenic fungi. Type I polyketide synthase (PKS-I) and non-ribosomal peptide synthetase (NRPS) were detected, which were indicative of the antifungal compounds that Streptomyces sp. CB-75 could produce. An ethyl acetate extract from the strain exhibited the lowest minimum inhibitory concentration (MIC) against Colletotrichum musae (ATCC 96167) (0.78µg/ml) and yielded the highest antifungal activity against Colletotrichum gloeosporioides (ATCC 16330) (50.0µg/ml). Also, spore germination was significantly inhibited by the crude extract. After treatment with the crude extract of Streptomyces sp. CB-75 at the concentration 2 x MIC, the pathogenic fungi showed deformation, shrinkage, collapse, and tortuosity when observed by scanning electron microscopy (SEM). By gas chromatography-mass spectrometry (GC-MS) of the crude extract, 18 chemical constituents were identified; (Z)-13-docosenamide was the major constituent. Pot experiments showed that the incidence of banana seedlings was reduced after using Streptomyces sp. CB-75 treatment. The disease index was 10.23, and the prevention and control effect was 83.12%. Furthermore, Streptomyces sp. CB-75 had a growth-promoting effect on banana plants. The chlorophyll content showed 88.24% improvement, the leaf area, root length, root diameter, plant height, and stem showed 88.24, 90.49, 136.17, 61.78, and 50.98% improvement, respectively, and the shoot fresh weight, root fresh weight, shoot dry weight, and root dry weight showed 82.38, 72.01, 195.33, and 113.33% improvement, respectively, compared with treatment of fermentation broth without Streptomyces sp. CB-75. Thus, Streptomyces sp. CB-75 is an important microbial resource as a biological control against plant pathogenic fungi and for promoting banana growth. [ABSTRACT FROM AUTHOR]

The genus Streptomyces under phylum actinobacteria has been recognized as a prolific source for the production of bioactive secondary metabolites. An actinobacterial strain designated as DST103 isolated from a wetland fresh water sediment of Tamdil Lake, Mizoram, Northeast, India was identified as Streptomyces cyaneofuscatus (KY287599) using 16SrRNA gene sequencing which shares 99.87% sequence similarity with Streptomyces cyaneofuscatus NRRL B-2570T. The strain showed broad spectrum antimicrobial activities against Gram negative bacteria (Escherichia coli MTCC 739 and Pseudomonas aeruginosa MTCC 2453), Gram positive bacteria (Micrococcus luteus NCIM 2170 and Staphylococcus aureus MTCC 96) and yeast pathogen Candida albicans MTCC 3017). The methanolic extract of the strain DST103 exhibited highest antimicrobial activity against E. coli (IC50 = 2.10 μg/mL) and minimum activity against S. aureus (IC50 = 43.63 μg/mL). Five antibiotics [trimethoprim (18 μg/g), fluconazole (6 μg/g), ketoconazole (18 μg/g), nalidixic acid (135 μg/g), and rifampicin (56 μg/g)] were detected and quantified using ultra-performance liquid chromatography (UPLC-ESI-MS/MS). Further, biosynthetic potential genes [polyketide synthases type II, non-ribosomal peptide synthetases, and aminodeoxyisochorismate synthase (phzE)] were also detected in strain DST103 which may possibly be responsible for the production of antimicrobial compounds. Additionally, gas chromatography-mass spectrometry analysis showed the presence of four volatile compounds which might be responsible for their diverse biological activity. The present study revealed the presence of bioactive compounds in strain DST103, which may be a promising resource for the discovery of novel bioactive metabolites against wide range of pathogens.

The objective of this study was to investigate the effect of environmental factors, namely temperature and water activity, on genes involved in the regulation of ochratoxin A (OTA) production over time. For this purpose, the previously characterized toxigenic Aspergillus carbonarius Ac29 isolate from Greek vineyards and the A. carbonarius ITEM 5010 reference strain were subjected to combined temperature and water activity (aw) treatments to study OTA production and relative gene expression. The fungal isolates were grown on a synthetic grape juice liquid medium (SGM) under different temperature (20 °C, 25 °C and 30 °C) and aw (0.94 and 0.98) regimes. The expression of the AcOTApks, AcOTAnrps, and laeA OTA related genes was investigated using real time PCR. Gene expression was monitored at the same time points, along with fungal biomass and OTA accumulation at three, six and nine days of incubation. In gene expression analysis, stimulation of the biosynthetic genes was observed a few days before any toxin could be detected. This fact may underline a possible early indicator of potential toxin contamination of grapes. However, the transcript levels varied with respect to the different combinations of ecophysiological conditions and time, highlighting a complex regulation of OTA related gene expression of A. carbonarius in the specific medium. [ABSTRACT FROM AUTHOR]