Microbial degradation, spectral analysis and toxicological assessment of malachite green by Streptomyces chrestomyceticus S20.

Malachite green (MG), a triphenylmethane dye is extensively used for coloring silk, aquaculture and textile industries, it has also has been reported toxic to life forms. This study aimed to investigate the biodegradation potential of MG by actinobacteria. The potent actinobacterial strain S20 used in this study was isolated from forest soil (Sabarimala, Kerala, India) and identified as Streptomyces chrestomyceticus based on phenotype and molecular features. Strain S20 degraded MG up to 59.65 ± 0.68% was studied in MSM medium and MG (300 mg l-1) and degradation was increased (90-99%) by additions of 1% glucose and yeast extract into the medium at pH 7. The treated metabolites from MG by S20 characterized by FT-IR and GC-MS. The results showed MG has been degraded into nontoxic compounds evaluated by (1) phytotoxic assay on Vigna radiata, (2) microbial toxicity on Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Streptococcus sp. and Escherichia coli, (3) cytotoxicity assay in a human cell line (MCF 7). The toxicity studies demonstrated that the byproducts from MG degradation by S. chrestomyceticus S20 were no toxic to plants and microbes and less toxic to human cells as compared to the parent MG. Perhaps this is the first work reported on biodegradation of MG by S. chrestomyceticus which could be a potential candidate for the removal of MG from various environments.

Understanding the molecular mechanisms for the enhanced phytoremediation of heavy metals through plant growth promoting rhizobacteria: A review.

Rapid industrialization, modern agricultural practices and other anthropogenic activities add a significant quantity of toxic heavy metals into the environment, which induces severe toxic effects on all form of living organisms, alter the soil properties and its biological activity. Remediation of heavy metal contaminated sites has become an urgent necessity. Among the existing strategies, phytoremediation is an eco-friendly and much convincing tool for the remediation of heavy metals. However, the applicability of phytoremediation in contaminated sites is restricted by two prime factors such as i) slow growth rate at higher metal contaminated sites and ii) metal bioavailability. This circumstance could be minimized and accelerate the phytoremediation efficiency by incorporating the potential plant growth promoting rhizobacterial (PGPR) as a combined approach. PGPR inoculation might improve the plant growth through the production of plant growth promoting substances and improve the heavy metal remediation efficiency by the secretion of chelating agents, acidification and redox changes. Moreover, rhizobacterial inoculation consolidates the metal tolerance and uptake by regulating the expression of various metal transporters, tolerant and metal chelator genes. However, the exact underlying molecular mechanism of PGPR mediated plant growth promotion and phytoremediation of heavy metals is poorly understood. Thus, the present review provides clear information about the molecular mechanisms excreted by PGPR strains in plant growth promotion and phytoremediation of heavy metals.

Isolation, characterization and identification of antibiofouling metabolite from mangrove derived Streptomyces sampsonii PM33.

In this study, we report the production, bioassay guided isolation and identification of antibiofouling metabolite from mangrove derived actinobacterium, Streptomyces sampsonii (PM33). The actinobacterial strain PM33 yields maximum amount of antifouling compounds through agar surface fermentation. In optimization, carbohydrates such as glucose, fructose and xylose, are suitable for maximum production of the active compound. In addition, other compounds such as malt extract, glutamine, and sodium chloride concentrations (2.5, 5 and 7.5%) and parameters such as pH 7.0 and temperature range 30 °C to 40 °C enhanced the production of antifouling metabolite. The antifouling metabolite was extracted in ethyl acetate. TLC and bioautography was used to separate and detect the antifouling metabolite present in the crude extract. The physico chemical features revealed that the antifouling metabolite PM33 - B as taxifolin (C15H12O7). The purified taxifolin was found to be active against biofouling bacteria, algal spore germination and mollusc foot adherence, respectively. Toxicity nature of taxifolin was also determined by adopting zebrafish embryos. The taxifolin isolated from mangrove-derived Streptomyces sampsonii PM33 is a promising candidate for the development of eco-friendly antifouling preparation.

Biocompatible silver, gold and silver/gold alloy nanoparticles for enhanced cancer therapy: in vitro and in vivo perspectives.

The aims of nano oncology are to detect, target and treat cancer cells without any side effects. The present study describes the microbial synthesis of biocompatible nanoparticles of silver (AgNPs), gold (AuNPs) and their alloy (Ag/AuNPs) for hepatoprotective activity against diethylnitrosamine (DEN)-induced liver cancer in a Sprague Dawley (SD) rat model. The crystalline nature and physicochemical features of the nanoparticles were identified by Fourier transform infra-red (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analysis. Based on the instrumental analysis, the synthesised nanomaterials were found to be spherical in shape and have an average size in the nano region. Nitrate reductase was characterized after partial purification of the culture filtrate via polyacrylamide gel electrophoresis and its molecular weight was determined as ∼45 kDa. Furthermore, the IC50 values of the AgNPs, AuNPs and Ag/AuNPs on HepG2 cells were determined as 38.42 µg ml-1, 43.25 µg ml-1 and 39.20 µg ml-1, respectively, and the antioxidant potential of the nanoparticles was also systematically analyzed. The No-Observed-Adverse-Effect-Level (NOAEL) for the AgNPs was determined to be 2000 mg per kg of body weight (bw) from an acute toxicity test. Similarly, the NOAEL of AuNPs and Ag/AuNPs were calculated as 1000 mg per kg bw. Based on the in vivo studies, a significant tumour reduction (∼45 to 65%) was observed in the nanoparticle-treated animals, which was further confirmed by hematological, biochemical, TEM and histopathological analysis. Immunohistochemistry analysis confirmed the presence of BAX antibodies, up to immunoreactive (3+) level in treated animals. These results strongly suggest the potential anticancer activities of AgNPs, AuNPs and Ag/AuNPs against DEN-induced liver cancer and they could be potential candidates for effective nano drug development.

Bio-medically active zinc oxide nanoparticles synthesized by using extremophilic actinobacterium, Streptomyces sp. (MA30) and its characterization.

The present study describes the synthesis of zinc oxide nanoparticles (ZnO-NPs) using an extremophilic actinobacterial cell-free extract, supplied with aqueous zinc acetate solution. Crystalline nature, morphological features, and polydispersed nanoparticles size (15-30 nm) were identified by X-ray diffraction (XRD), atomic force and electron microscopic analysis with dynamic light scattering (DLS) study. The interaction between biomolecules and ZnO-NPs was analyzed using Fourier transform infra-red spectroscopy (FT-IR). Furthermore antibacterial, antioxidant activities, and cell viability test of ZnO-NPs were systematically evaluated. The present study opens a new avenue for the actinobacterial synthesis of oxide nanoparticles.

Terpenoid bioactive compound from Streptomyces rochei (M32): taxonomy, fermentation and biological activities.

The present study emphasized the production of biologically active terpenoid compound from Streptomyces rochei M32, which was isolated from Western Ghats ecosystem, South India. The presence of resistant genes like mecA, vanA of Staphylococcus aureus and bla SHV, bla TEM of Pseudomonas aeruginosa was confirmed by molecular studies. The isolated compound from Streptomyces rochei M32 inhibited wide range of standard and clinical drug resistant pathogens and enteric pathogens. The rice bran supplemented basal medium influenced the active compound production on 8th day of fermentation and yielded 1875 mg of crude extract from 10 g of rice bran substrate. Purification and characterization of crude ethyl acetate extract was achieved by preparative thin layer chromatography. The active fraction was identified as terpenoid class compound by chemical screening. Based on the results of spectral studies (NMR, LC-MS, FTIR, etc.), the active compound was tentatively identified as 1, 19-bis (3-hydroxyazetidin-1-yl) nonadeca-5, 14-diene-1, 8, 12, 19-tetraone with molecular weight 462.41 g/mol. Minimum inhibitory concentration value ranges between 7.6 and 31.2 µg/mL against test organisms was observed. The cytotoxicity results on cervical cancer (HeLa) cell line showed IC50 value of 2.034 µg/mL. The corresponding compound is not previously reported from any microbial resources.

Antibiofouling potential of quercetin compound from marine-derived actinobacterium, Streptomyces fradiae PE7 and its characterization.

An attempt has been made to isolate, purify and characterize antifouling compound from Streptomyces fradiae PE7 isolated from Vellar estuarine sediment, Parangipettai, South India. The microbial identification was done at species level based on its phenotypic, cell wall and molecular characteristics. Strain PE7 produced high quantity of antifouling compounds in agar surface fermentation when compared to submerged fermentation. In fermentation optimization, wide range of sugars, amino acids, minerals, pH, temperature and NaCl concentration was found to influence the antifouling compound production from the strain PE7. Antifouling compound PE7-C was purified from the crude extract by preparative TLC, and its activity against biofouling bacteria was confirmed by bioautography. Based on the physico-chemical characteristics, the chemical structure of the antifouling compound PE7-C was identified as quercetin (C15H10O7), a flavonoid class of compound with the molecular weight 302.23 g/mol. The purified quercetin was active against 18 biofouling bacteria with MIC range between 1.6 and 25 µg/ml, algal spore germination and mollusc foot adherence found at 100 µg/ml and 306 ± 19.6 µg ml(-1) respectively. The present study, for the first time, reported quercetin from marine-derived Streptomyces sp. PE7 with antifouling activity. This also leads to the repurposing of quercetin for the development of antifouling agent.

Biomedical potential of actinobacterially synthesized selenium nanoparticles with special reference to anti-biofilm, anti-oxidant, wound healing, cytotoxic and anti-viral activities.

Currently, there is an ever-increasing need to develop environmentally benign processes in place of synthetic protocols. As a result, researchers in the field of nanoparticle synthesis are focusing their attention on microbes from rare biological ecosystems. One potential actinobacterium, Streptomyces minutiscleroticus M10A62 isolated from a magnesite mine had the ability to synthesize selenium nanoparticles (SeNPs), extracellularly. Actinobacteria mediated SeNP synthesis were characterized by UV-visible, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and high resolution transmission electron microscopy (HR-TEM) analysis. The UV-spectral analysis of SeNPs indicated the maximum absorption at 510nm, FT-IR spectral analysis confirms the presence of capping protein, peptide, amine and amide groups. The selenium signals confirm the presence of SeNPs. All the diffraction peaks in the XRD pattern and HR-TEM confirm the size of SeNPs in the range of 10-250nm. Further, the anti-biofilm and antioxidant activity of the SeNPs increased proportionally with rise in concentration, and the test strains reduced to 75% at concentration of 3.2µg. Selenium showed significant anti-proliferative activity against HeLa and HepG2 cell lines. The wound healing activity of SeNPs reveals that 5% selenium oinment heals the excision wound of Wistar rats up to 85% within 18 days compared to the standard ointment. The biosynthesized SeNPs exhibited good antiviral activity against Dengue virus. The present study concludes that extremophilic actinobacterial strain was a novel source for SeNPs with versatile biomedical applications and larger studies are needed to quantify these observed effects of SeNPs.

A study of the bactericidal, anti-biofouling, cytotoxic and antioxidant properties of actinobacterially synthesised silver nanoparticles.

Actinobacteria- mediated synthesis of silver nanoparticles (AgNPs) is a reliable, eco-friendly and important aspect of nanobiotechnology. In this study, aqueous silver ions, which were exposed to an actinobacterial biomass of Streptomyces naganishii (MA7), were reduced to form stable AgNPs under optimised conditions. The microbially synthesised AgNPs were characterised by UV-Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), atomic force microscopy (AFM) and high- resolution transmission electron microscopy (HR-TEM). The size (5-50 nm) and shape (spherical) of the AgNPs were determined. The biosynthesised AgNPs exhibited good bactericidal, anti-biofouling, antioxidant and cytotoxic effects with regards to the HeLa cell line. A single protein band with a molecular weight of 44 kDa was obtained after partial purification of the culture filtrate via polyacrylamide gel electrophoresis. The potent actinobacterial strain was identified by its molecular (16s rRNA sequencing), phenotypic and cultural characteristics. The current study demonstrated the potential use of the extremophilic actinobacterial strain of S. naganishii (MA7) as a novel source for AgNPs synthesis with improved biomedical applications.