A Secondary Metabolite of Cercospora sp., Associated with Rosa damascena Mill., Inhibits Proliferation, Biofilm Production, Ergosterol Synthesis and Other Virulence Factors in Candida albicans.

Here we describe the antimicrobial potential of secondary metabolites, fulvic acid (F.A.) and anhydrofulvic acid (AFA), produced by RDE147, an endophyte of Rosa damascena Mill. The endophyte was identified as Cercospora piaropi by ITS and ß-tubulin-based phylogenetic analyses, while chemoprofiling of the endophyte by column chromatography and spectroscopy yielded two pure compounds, F.A. and AFA. The compounds demonstrated different antimicrobial profiles, with AFA suppressing the growth of C. albicans at 7.3 µg ml-1 IC50. Further studies revealed that AFA strongly restricted the biofilm production and hyphae formation in C. albicans by down-regulating several biofilm and morphogenesis-related genes. The time-kill assays confirmed the fungicidal activity of AFA against C. albicans, killing 83.6% of the pathogen cells in 24 h at the MIC concentration, and the post-antibiotic effect (PAE) experiments established the suppression of C. albicans growth for extended time periods. The compound acted synergistically with amphotericin B and nystatin and reduced ergosterol biosynthesis by the pathogen, confirmed by ergosterol estimation and comparative expression profiling of selected genes and molecular docking of AFA with C. albicans squalene epoxidase. AFA also suppressed the expression of several other virulence genes of the fungal pathogen. The study determines the anti-C. albicans potential of AFA and its impact on the biology of the pathogen. It also indicates that Cercospora species may yield potential bioactive molecules, especially fulvic acid derivatives. However, it is imperative to conduct in vivo studies to explore this molecule's therapeutic potential further.

Setomimycin as a potential molecule for COVID­19 target: in silico approach and in vitro validation.

COVID-19 pandemic caused by the SARS-CoV-2 virus has led to a worldwide crisis. In view of emerging variants time to time, there is a pressing need of effective COVID-19 therapeutics. Setomimycin, a rare tetrahydroanthracene antibiotic, remained unexplored for its therapeutic uses. Herein, we report our investigations on the potential of setomimycin as COVID-19 therapeutic. Pure setomimycin was isolated from Streptomyces sp. strain RA-WS2 from NW Himalayan region followed by establishing in silico as well as in vitro anti-SARS-CoV-2 property of the compound against SARS-CoV-2 main protease (Mpro). It was found that the compound targets Mpro enzyme with an IC50 value of 12.02 ± 0.046 µM. The molecular docking study revealed that the compound targets Glu166 residue of Mpro enzyme, hence preventing dimerization of SARS-CoV-2 Mpro monomer. Additionally, the compound also exhibited anti-inflammatory and anti-oxidant property, suggesting that setomimycin may be a viable option for application against COVID-19 infections.

Protective effect of Bacillus species associated with Rumex dentatus against postharvest soil borne disease in potato tubers and GC-MS metabolite profile.

Potato is constantly exposed to various kinds of phytopathogens which cause diseases during the developmental stage and post-harvest storage. This investigation was designed to assay the anti-phytopathogen activity of bacterial endophytes and their suppressive effects on rot disease in potato. The study also aimed to screen isolates for their plant growth-promoting traits and establish GC-MS-based metabolite profile of the potent isolate. Endophytes were isolated from Rumex dentatus and identified based on 16S rRNA gene. They were screened in dual culture assay against fungal phytopathogens and the potent isolate was tested for its capability to suppress Fusarium rot disease in potato tubers. The mechanism of action of endophytes on the phytopathogens was assessed using scanning electron microcopy. Isolates were also screened in vitro to assay their capability to produce phytohormones, hydrolytic enzymes, and to solubilize phosphates. Endophytic isolates produced proteases with a diameter of halo zone ranging from 7 to 32 mm. Bacillus sp. KL5 exhibited the highest production of indole acetic acid (IAA) with the amount of 104.28 µg/mL and was the most potent antagonist of Fusarium oxysporum and Verticillium dahliae with an inhibitory percentage of 61.53 and 100%, respectively. It showed a reduction of potato rot disease severity by more than 50%. GC-MS of active fractions of KL5 showed the presence of dibutylphthalate and 2,4-di-tert-butylphenol as major metabolites. From this study, it is evident that endophytic Bacillus species from R. dentatus are potent antagonists of F. oxysporum and V. dahliae. Bacillus sp. KL5 is a potent inhibitor of pathogenic F. oxysporum in potato tubers and can be developed as a biocontrol agent.

A review on Arthrobacter sp. lipase: A versatile biocatalyst for the kinetic resolution to access enantiomerically pure/enriched compounds.

Over the last few years, there has been a dramatic increase in the number of reports related to Arthrobacter sp. lipase (ABL:MTCC No. 5125) catalyzed kinetic resolution performed in biphasic media. A strain displaying esterase/lipase activity and designated as ABL was isolated, during the course of a screening program at Indian Institute of Integrative Medicine, Jammu. Considerable research has shown that reactions catalyzed by ABL are more selective than many commercial lipases. Since new applications of this lipase are emerging, there is a great need to provide all the relevant information exclusively. This review article is an attempt to cover all the relevant reports based on isolation, purification, immobilization, and application of ABL in the biopharmaceutical sector.

Isolation and Characterization of Serratiopeptidase Producing Bacteria from Mulberry Phyllosphere.

Serratiopeptidase (EC 3.4.24.40), a proteolytic enzyme, is one of the most promising enzymes being used in biopharmaceutical industry. Mulberry phyllosphere, being an unexplored niche for exploration of protease production, was chosen for the present study. Protease producing bacteria were isolated from the tissues of mulberry plant as well as its rhizospheric soil. Two protease producing bacteria belonging to Serratia genus were found to be potential serratiopeptidase producers. Among them, the endophyte, i.e., Serratia marcescens MES-4 presented 95 Units/mL activity, while the soil isolate i.e., Serratia marcescens MRS-11 presented 156 Units/mL activity.

Lipovelutibols A-D: Cytotoxic Lipopeptaibols from the Himalayan Cold Habitat Fungus Trichoderma velutinum.

Four novel lipovelutibols A (1), B (2), C (3), and D (4) containing six amino acid residues with leucinol at the C-terminus and a fatty acyl moiety (n-octanoyl) at its N-terminus were isolated from the psychrotrophic fungus Trichoderma velutinum collected from the Himalayan cold habitat. The structures (1-4) were determined by NMR and MS/MS, and the stereochemistry of amino acids by Marfey's method. Lipopeptaibols 2 and 4 were found to contain d-isovaline, a nonproteinogenic amino acid, but lacked α-aminoisobutyric acid, characteristic of peptaibols. Cytotoxic activity of 2 and 4 was observed against HL-60, LS180, MDA-MB-231, and A549 cancer cell lines.

An Insight into the Secondary Metabolism of Muscodor yucatanensis: Small-Molecule Epigenetic Modifiers Induce Expression of Secondary Metabolism-Related Genes and Production of New Metabolites in the Endophyte.

Muscodor spp. are proficient producers of bioactive volatile organic compounds (VOCs) with many potential applications. However, all members of this genus produce varying amounts and types of VOCs which suggests the involvement of epigenetics as a possible explanation. The members of this genus are poorly explored for the production of soluble compounds (extrolites). In this study, the polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes from an endophyte, Muscodor yucatanensis Ni30, were cloned and sequenced. The PKS genes belonged to reduced, partially reduced, non-reduced, and highly reduced subtypes. Strains over-expressing PKS genes were developed through the use of small-molecule epigenetic modifiers (suberoylanilide hydroxamic acid (SAHA) and 5-azacytidine). The putative epigenetic variants of this organism differed considerably from the wild type in morphological features and cultural characteristics as well as metabolites that were produced. Each variant produced a different set of VOCs distinct from the wild type, and several VOCs including methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)hexane-2,4-diol and 2-carboxymethyl-3-n-hexylmaleic appeared in the variant strains, the production of which could be attributed to the activity of otherwise silent PKS genes. The bioactive extrolite brefeldin A was isolated and characterized from the wild type. However, this metabolite was not detected in EV-1, but instead, two other products were isolated and characterized as ergosterol and xylaguaianol C. Hence, M. yucatanensis has the genetic potential to produce several previously undetectable VOCs and organic solvent soluble products. It is also the case that small-molecule epigenetic modifiers can be used to produce stable variant strains of fungi with the potential to produce new molecules. Finally, this work hints to the prospect that the epigenetics of an endophytic microorganism can be influenced by any number of environmental and chemical factors associated with its host plant which may help to explain the enormous chemical diversity of secondary metabolic products found in Muscodor spp.

Optimization of nonribosomal peptides production by a psychrotrophic fungus: Trichoderma velutinum ACR-P1.

Trichoderma is an anamorphic filamentous fungal genus with immense potential for production of small valuable secondary metabolites with indispensable biological activities. Microbial dynamics of a psychrotrophic strain Trichoderma velutinum ACR-P1, isolated from unexplored niches of the Shiwalik region, bestowed with rich biodiversity of microflora, was investigated for production of nonribosomal peptides (NRPs) by metabolite profiling by intact-cell mass spectrometry (ICMS) employing matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometer. Being the first report on NRPs production by T. velutinum, studies on optimization of growth conditions by Response Surface Methodology (RSM) for production of NRPs by ACR-P1 was carried out strategically. Multifold enhancement in the yield of NRPs belonging to subfamily SF4 with medium chain of amino acid residues having m/z 1437.9, 1453.9, and 1452.0 at pH 5.9 at 20 °C and of subfamily SF1 with long-chain amino acid residues having m/z 1770.2, 1784.2, 1800.1, 1802.1, and 1815.1 was achieved at pH 7.0 at 25 °C. Complexities of natural mixtures were thus considerably reduced under respective optimized culture conditions accelerating the production of novel microbial natural products by saving time and resources.

Secondary Metabolites from Endophytic Fungus Penicillium pinophilum Induce ROS-Mediated Apoptosis through Mitochondrial Pathway in Pancreatic Cancer Cells.

The endophytic fungus strain MRCJ-326, isolated from Allium schoenoprasum, which is also known as Snow Mountain Garlic or Kashmiri garlic, was identified as Penicillium pinophilum on the basis of morphological characteristics and internal transcribed spacer region nucleotide sequence analysis. The endophytic fungus extract was subjected to 2D-SEPBOX bioactivity-guided fractionation and purification. The anthraquinone class of the bioactive secondary metabolites were isolated and characterized as oxyskyrin (1), skyrin (2), dicatenarin (3), and 1,6,8-trihydroxy-3-hydroxy methylanthraquinone (4) by spectral analysis. Dicatenarin and skyrin showed marked growth inhibition against the NCI60/ATCC panel of human cancer cell lines with least IC50 values of 12 µg/mL and 27 µg/mL, respectively, against the human pancreatic cancer (MIA PaCa-2) cell line. The phenolic hydroxyl group in anthraquinones plays a crucial role in the oxidative process and bioactivity. Mechanistically, these compounds, i.e., dicatenarin and skyrin, significantly induce apoptosis and transmit the apoptotic signal via intracellular reactive oxygen species generation, thereby inducing a change in the mitochondrial transmembrane potential and induction of the mitochondrial-mediated apoptotic pathway. Our data indicated that dicatenarin and skyrin induce reactive oxygen species-mediated mitochondrial permeability transition and resulted in an increased induction of caspase-3 apoptotic proteins in human pancreatic cancer (MIA PaCa-2) cells. Dicatenarin showed a more pronounced cytotoxic/proapopotic effect than skyrin due to the presence of an additional phenolic hydroxyl group at C-4, which increases oxidative reactive oxygen species generation. This is the first report from P. pinophilum secreating these cytotoxic/proapoptotic secondary metabolites.

Cloning and functional characterization of nitrilase from Fusarium proliferatum AUF-2 for detoxification of nitriles.

A fungal nitrilase gene from Fusarium proliferatum AUF-2 was cloned through reverse transcription-PCR. The open reading frame consisted of 903 bp and potentially encoded a protein of 301 amino acid residues with a theoretical molecular mass of 33.0 kDa. The encoding gene was expressed in Escherichia coli strain BL21 and the recombinant protein with His6-tag was purified to electrophoretic homogeneity. The purified enzyme exhibited optimal activity in the range of 35-40 °C and pH 8.0. EDTA, Mg(2+), Zn(2+), Ca(2+), Fe(2+), Fe(3+) and Mn(2+) stimulated hydrolytic activity, whereas Cu(2+), Co(2+) and Ni(2+) had inhibitory effect on nitrilase activity. Ag(+) ions showed a strong inhibitory effect on the recombinant nitrilase activity. This nitrilase was specific towards aliphatic, heterocyclic and aromatic nitriles. The kinetic parameters V(max) and K(m) for benzonitrile substrate were determined to be 14.6 µmol/min/mg protein and 1.55 mM, respectively. Homology modelling and molecular docking studies provided an insight into the substrate specificity and the proposed catalytic triad for recombinant nitrilase consisted of Glu-54, Lys-133 and Cys-175. This is the first report on the cloning and heterologous expression of nitrilase from Fusarium proliferatum.

Engineering synthetic recursive pathways to generate non-natural small molecules.

Recursive pathways are broadly defined as those that catalyze a series of reactions such that the key, bond-forming functional group of the substrate is always regenerated in each cycle, allowing for a new cycle of reactions to begin. Recursive carbon-chain elongation pathways in nature produce fatty acids, polyketides, isoprenoids and α-keto acids (αKAs), which all use modular or iterative approaches for chain elongation. Recently, an artificial pathway for αKA elongation has been built that uses an engineered isopropylmalate synthase to recursively condense acetyl-CoA with αKAs. This synthetic approach expands the possibilities for recursive pathways beyond the modular or iterative synthesis of natural products and serves as a case study for understanding the challenges of building recursive pathways from nonrecursive enzymes. There exists the potential to design synthetic recursive pathways far beyond what nature has evolved.

Purification, functional characterization and enhanced production of serratiopeptidase from Serratia marcescens MES-4: An endophyte isolated from Morus rubra.

Serratiopeptidase, a proteolytic enzyme serves as an important anti-inflammatory and analgesic medication. Present study reports the production and purification of extracellular serratiopeptidase from an endophyte, Serratia marcescens MES-4, isolated from Morus rubra. Purification of the enzyme by Ion exchange chromatography led to the specific activity of 13,030 U/mg protein of serratiopeptidase, showcasing about 3.1 fold enhanced activity. The catalytic domain of the purified serratiopeptidase, composed of Zn coordinated with three histidine residues (His 209, His 213, and His 219), along with glutamate (Glu 210) and tyrosine (Tyr 249). The molecular mass, as determined by SDS-PAGE was ∼51 kDa. The purified serratiopeptidase displayed optimal activity at pH 9.0, temperature 50°C. Kinetic studies revealed Vmax and Km values of 33,333 U/mL and 1.66 mg/mL, respectively. Further, optimized conditions for the production of serratiopeptidase by Taguchi design led to the productivity of 87 U/mL/h with 87.9 fold enhanced production as compared to the previous conditions.

Identification and taxonomy of Streptomyces justiciae strain RA-WS2: a novel setomimycin producing actinobacterium.

The taxonomic position of novel bianthraquinone antibiotic producer Streptomyces strain RA-WS2, a soil isolate from Shivalik region of NW Himalayas, India, has been described. The isolate produces Setomimycin as a major secondary metabolite under defined submerged fermentation conditions. 16S rRNA partial gene sequencing of the isolate indicated its closest similarity (99.4%) with Streptomyces cyaneochromogenes, followed by Streptomyces aquilus. However, the morphological characteristics i.e. colony colour, mycelium and spore chain arrangement were found to be close to Streptomyces aquilus. Therefore, a polyphasic approach was used for taxonomic positioning of the isolate. The Whole genome based similarity with 88.4% dDDH value, 98.65% ANI and 96.99% AAI value indicated its closest identity with Streptomyces justiciae. The taxonomic characteristics such as white colony with smooth surface, cylindrical spores arranged in straight chain, diffusible melanin production, high salt tolerance, 16S rRNA gene sequencing and phylogenomic studies, led to the identification of the strain as Streptomyces justiciae RA-WS2. The predicted biosynthetic gene clusters further confirmed the presence of the BGC for setomimycin biosynthesis in Streptomyces justiciae strain RA-WS2. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03459-5.

A biostatistical approach for augmenting rare bianthraquinone antibiotic production by Streptomyces sp. RA-WS2 using Taguchi design.

Consistent production of bioactives from microbial sources remains a big challenge for fermentation based bio-processes. Setomimycin, a rare 9,9'-bianthrylanthracene antibiotic reported to be active against Gram positive bacteria i.e. Staphyloccocus aureus, Bacillus subtilis, Bacillus cereus, and Mycobacterium smegmatis, including mycobacteria is one of the least exploited antibiotic. Present work aims to enhance and maximize setomimycin production using One Factor at a Time (OFAT) approach, followed by Taguchi L9 orthogonal array (OA) design in 30L fermenter. Four most influential parameters, namely carbon source, nitrogen source, air and agitation were selected for optimization studies. The optimized production medium supplemented with 150 g/L glycerol and 7.5 g/L soyabean meal with an agitation rate of 100 RPM and air flow rate of 20 LPM (Liters Per Minute) resulted in 675 mg/L setomimycin production within 96-108 h of fermentation as compared to the initial production i.e. 40 mg/L. Thus, an overall enhancement of 16.8 folds was achieved in setomimycin production after optimization in 30L fermenter.

Isolation and anticancer activity evaluation of rare Bisaryl anthraquinone antibiotics from novel Streptomyces sp. strain of NW Himalayan region.

Biosynthesis of bisaryl preanthraquinone antibiotics by various microorganisms differs in monomeric subunits as well as their dimerization positions leading to different configurations. The present study relates to the production of rare bisaryl anthraquinone antibiotics by a new Streptomyces strain isolated from Shivalik region of NW Himalayas. In vitro anticancer and anti-migratory effects of Setomimycin (9,9' bisanthraquinone antibiotic) was seen with a significant reduction in the expression of both MEK as well as ERK pathways in a dose dependent manner at 6.5 µM & 8 µM concentration in HCT-116 and 5.5 µM & 7 µM concentration in MCF-7 cells. In vivo studies in aggressive orthotopic mouse mammary carcinoma model (4T1) demonstrated about 76% reduction of primary tumor weight and 90.5% reduction in the tumor volume within two weeks. In vivo pharmacokinetics study of setomimycin revealed that it can be rapidly absorbed with an adequate plasma exposure and half-life which can be linked to its in vivo efficacy.

Purification and characterization of thermoactive serratiopeptidase from Serratia marcescens AD-W2.

Serratiopeptidase is a proteolytic enzyme extensively used as an anti-inflammatory and analgesic drug. Present work reports a thermoactive serratiopeptidase from Serratia marcescens AD-W2, a soil isolate from the North-Western Himalayan region of India. The extracellular metalloprotease has been purified by a simple two-step procedure resulting in a specific activity of 20,492 Units/mg protein with 5.28-fold purification. The molecular mass of the metalloprotease, as determined by SDS-PAGE was ~ 51 kDa. The purified serratiopeptidase presented optimum activity at pH 9.0, temperature 50 °C and stability in wide pH and temperature range. Critical temperature of 50 °C confirmed the thermoactivity of the purified serratiopeptidase. The kinetic studies of the purified serratiopeptidase revealed Vmax and Km of 57,256 Units/mL and 1.57 mg/mL, respectively, for casein. The purified serratiopeptidase from S. marcescens AD-W2 was found to be 100% identical to serralysin from Serratia marcescens ATCC 21074/E-15. The catalytic domain comprising of Zn coordinated with three histidine residues (His192, His196, His202), along with glutamate (Glu193) and tyrosine (Tyr232) residues, further confirmed that the purified protein is identical to serralysin.

Discovery of a Secalonic Acid Derivative from Aspergillus aculeatus, an Endophyte of Rosa damascena Mill., Triggers Apoptosis in MDA-MB-231 Triple Negative Breast Cancer Cells.

A new secalonic acid derivative, F-7 (1), was isolated from the endophytic Aspergillus aculeatus MBT 102, associated with Rosa damascena. The planar structure of 1 was established on the basis of 1D and 2D NMR and ESI-TOF-MS spectra. The relative configuration of 1 was determined applying a combined quantum mechanical/NMR approach and, afterward, the comparison of calculated and experimental electronic circular dichroism spectra determined the assignment of its absolute configuration. The compound possesses strong cytotoxic activity against triple negative breast cancer (TNBC) cells. It was found to induce apoptosis, as evidenced by scanning electron microscopy and phase contrast microscopy. Furthermore, flow cytometry analyses demonstrated that 1 induced mitochondrial damage and reactive oxygen species mediated apoptosis, arresting the G1 phase of the cells in a dose-dependent manner. Also, the compound causes significant microtubule disruption in TNBC cells. Subsequently, 1 restricted the cell migration leading to the concomitant increase in expression of cleaved caspase and PARP.

Arthrobacter sp. lipase immobilization for preparation of enantiopure masked beta-amino alcohols.

Recent reports on immobilization of lipase from Arthrobacter sp. (ABL, MTCC 5125; IIIM isolate) on insoluble polymers have shown altered properties including stability and enantioselectivity. Present work demonstrates a facile method for the preparation of enantiopure beta-amino alcohols by modulation of ABL enzyme properties via immobilization on insoluble as well as soluble supports using entrapment/covalent binding techniques. Efficacies of immobilized ABL on insoluble supports prepared from tetraethylorthosilicate/aminopropyltriethoxy silane and soluble supports derived from copolymerization of N-vinyl pyrrolidone-allylglycidyl ether (ANP type)/N-vinyl pyrrolidone-glycidyl methacrylate (GNP type) for kinetic resolution of masked beta-amino alcohols have been studied vis-à-vis free ABL enzyme/wet cell biomass. The immobilized lipase on different insoluble/soluble supports has shown 21-110 mg/g protein binding and 30-700 U/g activity for hydrolyzing tributyrin substrate. The findings have shown a significant enhancement in enantioselectivity (ee 99%) vis-à-vis wet cell biomass providing ee 70-90% for resolution of beta-amino alcohols.

Isolation of depsipeptides and optimization for enhanced production of valinomycin from the North-Western Himalayan cold desert strain Streptomyces lavendulae.

Exploration of microbial dynamics of Streptomyces lavendulae ACR-DA1, a psychrotrophic isolate from the North-Western Himalayan cold desert, was carried out using matrix-assisted laser desorbtion ionisation-time of flight mass spectrometer. Valinomycin was found as a major produce and cyclic depsipeptide montanastatin as a minor produce. The yield of the valinomycin was found to be 0.3 mg l-1 in submerged growth condition at the batch scale. Miniaturization of optimization experiments was adept to maximize the production using the expeditious and efficient technique of intact cell mass spectrometry. The present study showed that using optimized conditions and growing the culture in synthetic mineral base starch medium at 10 °C enhanced the production to 19.4 mg l-1. Our results demonstrated 64-fold increase in yield from the wild-type S. lavendulae ACR-DA1 strain using a simple and economical downstream process.