Antibacterial p-terphenyl and α‑pyrone derivates isolated from the marine-derived actinomycete Nocardiopsis sp. HDN154086

Assisted by OSMAC strategy, one new p-terphenyl and two new α‑pyrone derivates, namely nocarterphenyl I (1) and nocardiopyrone D-E (2-3), were obtained and characterized from the marine sediment-derived actinomycete Nocardiopsis sp. HDN154086. The structures of these compounds were determined on the basis of MS, NMR spectroscopic data and single-crystal X-ray diffraction. Compound 1 with a rare 2,2'-bithiazole structure among natural products showed promising activity against five bacteria with MIC values ranging from 0.8 to 1.6 μM and 3 exhibited notable antibacterial activity against MRSA compared the positive control ciprofloxacin.

Bioprospecting the potential of metabolites from a Saharan saline soil strain Nocardiopsis dassonvillei GSBS4

Saharan soil samples collected in El-Oued province have been investigated for actinobacteria as a valuable source for the production of bioactive metabolites. A total of 273 isolates were obtained and subjected to antagonistic activity tests against human pathogenic germs. A strain with a broad-spectrum antimicrobial activity was selected and identified as Nocardiopsis dassonvillei GSBS4, with high sequence similarities to N. dassonvillei subsp. dassonvilleiT X97886.1 (99%) based on polyphasic taxonomy approach and 16S ribosomal ribonucleic acid gene sequence analysis. The GSBS4 ethyl acetate crude extract showed strong antibacterial activity towards pathogenic bacteria and Candida albicans. It inhibited biofilm formation by Staphylococcus aureus and methicillin-resistant S. aureus with minimum inhibitory concentrations estimated at 0.144 and 1.15 mg·mL-1 , respectively. A 44% biofilm reduction was obtained for S. aureus and 61% for Pseudomonas aeruginosa. Furthermore, phenols composition of the crude extract showed a significant dose-dependent antioxidant activity by α-diphenyl-β-picrylhydrazyl (57.21%) and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (64.29%) radicals scavenging assays. Although no inhibition was obtained on human coronavirus human coronavirus (HCoV) 229E and on model enterovirus (poliovirus 1) infection, a dose-dependent increase in cell viability of HCoV 229E-infected cells was noticed as the viability increased from 21% to 37%. Bioassay-guided fractionation of the crude extract gave a fraction showing antibacterial activity, which was analyzed by liquid chromatography-electrospray mass spectrometric technique, providing structural features on a major purple metabolite.

Co-application of citric acid and Nocardiopsis sp. strain RA07 enhances phytoremediation potentiality of Sorghum bicolor L

This study investigated the combined effects of citric acid (CA) and Nocardiopsis sp. RA07 on the phytoremediation potential of lead (Pb)- and copper (Cu)-contaminated soils by Sorghum bicolor L. The strain RA07 was able to tolerate Pb and Cu, and exhibited plant growth-promoting features like siderophore production, indole-3-acetic acid (IAA) synthesis, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and phosphate solubilization. The combined application of CA and strain RA07 significantly increased S. bicolor growth, chlorophyll content and antioxidant enzymatic activity, and decreased oxidative stress (hydrogen peroxide and malondialdehyde content) under Pb and Cu stress circumstances as compared to individual treatments (i.e., CA and strain RA07). Furthermore, the combined application of CA and RA07 significantly enhanced S. bicolor ability to accumulate Pb and Cu by 64.41% and 60.71% in the root and 188.39% and 125.56% in the shoot, respectively, as compared to the corresponding uninoculated plants. Our results indicate that inoculation of Nocardiopsis sp. together with CA could be a useful practical approach to mitigate Pb and Cu stress on plant growth and increase the effectiveness of phytoremediation in Pb- and Cu-polluted soils.

New Pyrroline Isolated from Antarctic Krill-Derived Actinomycetes Nocardiopsis sp. LX-1 Combining with Molecular Networking

Antarctic krill (Euphausia superba) of the Euphausiidae family comprise one of the largest biomasses in the world and play a key role in the Antarctic marine ecosystem. However, the study of E. superba-derived microbes and their secondary metabolites has been limited. Chemical investigation of the secondary metabolites of the actinomycetes Nocardiopsis sp. LX-1 (in the family of Nocardiopsaceae), isolated from E. superba, combined with molecular networking, led to the identification of 16 compounds a-p (purple nodes in the molecular network) and the isolation of one new pyrroline, nocarpyrroline A (1), along with 11 known compounds 2-12. The structure of the new compound 1 was elucidated by extensive spectroscopic investigation. Compound 2 exhibited broad-spectrum antibacterial activities against A. hydrophila, D. chrysanthemi, C. terrigena, X. citri pv. malvacearum and antifungal activity against C. albicans in a conventional broth dilution assay. The positive control was ciprofloxacin with the MIC values of <0.024 µM, 0.39 µM, 0.39 µM, 0.39 µM, and 0.20 µM, respectively. Compound 1 and compounds 7, 10, and 11 displayed antifungal activities against F. fujikuroi and D. citri, respectively, in modified agar diffusion test. Prochloraz was used as positive control and showed the inhibition zone radius of 17 mm and 15 mm against F. fujikuroi and D. citri, respectively. All the annotated compounds a-p by molecular networking were first discovered from the genus Nocardiopsis. Nocarpyrroline A (1) features an unprecedented 4,5-dihydro-pyrrole-2-carbonitrile substructure, and it is the first pyrroline isolated from the genus Nocardiopsis. This study further demonstrated the guiding significance of molecular networking in the research of microbial secondary metabolites.

Identification of Novel Sphydrofuran-Derived Derivatives with Lipid-Lowering Activity from the Active Crude Extracts of Nocardiopsis sp. ZHD001

Lipid-lowering is one of the most effective methods of prevention and treatment for cardiovascular diseases. However, most clinical lipid-lowering drugs have adverse effects and cannot achieve the desired efficacy in some complex hyperlipidemia patients, so it is of great significance to develop safe and effective novel lipid-lowering drugs. In the course of our project aimed at discovering the chemical novelty and bioactive natural products of marine-derived actinomycetes, we found that the organic crude extracts (OCEs) of Nocardiopsis sp. ZHD001 exhibited strong in vivo efficacies in reducing weight gain, lowering LDL-C, TC, and TG levels, and improving HDL-C levels in high-fat-diet-fed mice models. Chemical investigations of the active OCEs led to identifying two new sphydrofuran-derived compounds (1-2) and one known 2-methyl-4-(1-glycerol)-furan (3). Their structures were elucidated by the analysis of HRESIMS, 1D and 2D NMR spectroscopic data, and ECD calculations. Among these compounds, compound 1 represents a novel rearranged sphydrofuran-derived derivative. Bioactivity evaluations of these pure compounds showed that all the compounds exhibited significant lipid-lowering activity with lower cytotoxicity in vitro compared to simvastatin. Our results demonstrate that sphydrofuran-derived derivatives might be promising candidates for lipid-lowering drugs.

Nocardiopsis akebiae sp. nov., a novel endophytic actinomycete isolated from fruits of Akebia trifoliata

A novel actinobacterium, designated strain HDS12^T, was isolated from fruits collected from Changde city located in the northwest of Hunan Province, China and characterized using a polyphasic approach. The 16S rRNA gene sequence analysis indicated that strain HDS12^T belonged to the genus Nocardiopsis, and had highest similarities to N. dassonvillei subsp. dassonvillei CGMCC 4.1231^T (99.79%), N. deserti H13^T (99.73%), N. alborubida NBRC 13392^T (99.66%), N. dassonvillei subsp. crassaminis D1^T (99.64%), N. synnemataformans DSM 44143^T (99.45%), N. lucentensis DSM 44048^T (99.04%), N. aegyptia DSM 44442^T (98.90%), N. flavescens CGMCC 4.5723^T (98.76%), N. alba DSM 43377^T (98.69%) and N. halotolerans DSM 44410^T (98.63%), respectively. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain HDS12^T formed an independent subclade, suggesting that strain HDS12^T could belong to a potential novel species. Phylogenomic analysis demonstrated that strain HDS12^T was closely related to N. dassonvillei subsp. dassonvillei CGMCC 4.1231^T and N. dassonvillei subsp. crassaminis D1^T. However, the average nucleotide identity value and the digital DNA-DNA hybridization value between them were well below 95-96% and 70% cut-off point recommended for delineating species. Based on its phenotypic and chemotaxonomic characteristics, strain HDS12^T (= MCCC 1K06173^T = JCM 34708^T) represents the type strain of a novel species, for which the name Nocardiopsis akebiae sp. nov. is proposed.

Structural Characterization, Antimicrobial, Antibiofilm, Antioxidant, Anticancer and Acute Toxicity Properties of N-(2-hydroxyphenyl)-2-phenazinamine From Nocardiopsis exhalans (KP149558)

The present study aimed to isolate and identify potential drugs from marine actinomycete Nocardiopsis exhalans and screen them for biomedical applications. The cell-free culture of N. exhalans was extracted with ethyl acetate and the solvent extract showed six fractions in thin-layer chromatography. The fractions were subjected to column chromatography for purification and evaluated for activity against human clinical pathogens. Fraction 4 showed significant activity and was identified as N-(2-hydroxyphenyl)-2-phenazinamine (NHP) using spectral analyses. Further, NHP showed excellent biofilm inhibitory activity against human clinical pathogens Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The in vitro antioxidant activity confirmed that NHP is scavenging the oxidative stress-enhancing molecules. The anti-proliferative activity of NHP against human breast cancer cells showed significant activity at 300 µg/ml and less cytotoxic activity against normal cells. Additionally, the toxicity assessment against zebrafish revealed that NHP does not cause any toxicity in the important organs. The results highlight N. exhalans as a promising candidate for the development of antibiotics with potential therapeutic applications.

Lipolytic Nocardiopsis for reduction of pollution load in textile industry effluent and SWISS model for structural study of lipase

The aim of this work was to study the reduction of pollution load in the textile industry effluent by lipase producing Nocardiopsis alba. Nocardiopsis alba was isolated from the soap-stock of an oil refinery located in North Gujarat, India. Lipase 2 (EC 3.1.1.3) protein sequence was identified from Nocardiopsis alba and the 3D model was predicted by SWISS Modeling. Lipolytic Nocardiopsis alba showed 84 ± 0.3 %, 75 ± 0.4 %, and 81 ± 0.3 % reduction of Chemical Oxygen Demand, Biochemical Oxygen Demand and Total Solids, respectively when was grown in textile industrial wastewater at 37 ± 1 °C, 120 rpm for 15 days. The findings of this research offer potential environmental benefits along with socio-economic benefits as well if implemented suitably.

An actinomycete strain of Nocardiopsis lucentensis reduces arsenic toxicity in barley and maize

Accumulation of arsenic in plant tissues poses a substantial threat to global crop yields. The use of plant growth-promoting bacterial strains to mitigate heavy metal toxicity has been illustrated before. However, its potential to reduce plant arsenic uptake and toxicity has not been investigated to date. Here, we describe the identification and characterization of a Nocardiopsis lucentensis strain isolated from heavy metal contaminated soil. Inoculation with this bioactive actinomycete strain decreased arsenic root and shoot bioaccumulation in both C3 and C4 crop species namely barley and maize. Upon arsenate treatment, N. lucentensis S5 stimulated root citric acid production and the plant's innate detoxification capacity in a species-specific manner. In addition, this specific strain promoted biomass gain, despite substantial tissue arsenic levels. Detoxification (metallothionein, phytochelatin, glutathione-S-transferase levels) was upregulated in arsenate-exposed shoot and roots, and this response was further enhanced upon S5 supplementation, particularly in barley and maize roots. Compared to barley, maize plants were more tolerant to arsenate-induced oxidative stress (less H₂O₂ and lipid peroxidation levels). However, barley plants invested more in antioxidative capacity induction (ascorbate-glutathione turnover) to mitigate arsenic oxidative stress, which was strongly enhanced by S5. We quantify and mechanistically discuss the physiological and biochemical basis of N. lucentensis-mediated plant biomass recovery on arsenate polluted soils. Our findings substantiate the potential applicability of a bactoremediation strategy to mitigate arsenic-induced yield loss in crops.

A novel substituted derivative of sterol from marine actinomycetes Nocardiopsis alba MCCB 110 antagonistic to the aquaculture pathogen Vibrio harveyi

In an attempt to screen antagonistic microorganisms from marine environment for the management of bacterial pathogens in aquaculture, an isolate of actinomycete MCCB 110 was segregated based on its comparatively higher inhibitory property on Vibrio harveyi (MCCB 111) and profound luminescent inhibition. Based on the culture characteristics, cell wall fatty acid profile and the nucleotide sequence of the 16S rRNA gene (1495 bp), the isolate was identified as Nocardiopsis alba. Solvent extraction of the fermentation broth followed by TLC and HPLC analyses resulted in the isolation of a major fraction active against luminescent Vibrio harveyi. Partial characterization of this bioactive fraction based on spectroscopic data obtained from FT-IR, UV, MS-MS and ¹H NMR analyses identified it as a substituted derivative of sterol, and was recognized to differ from those reportedly produced by the same genus. The fraction was not toxic to VERO cell line and shrimp haemocytes up to 1000 ppm tested. The study demonstrated the potential of the putative probiotic Nocardiopsis alba (MCCB 110) and its novel extra-cellular bioactive product in the management of Vibrio harveyi in aquaculture.