Isotropic Silver Nanoparticles from Cytobacillus kochii Strain SW6 Isolated from Bay of Bengal Sea Sediment Water and Their Antimicrobial, Antioxidant, and Catalytic Potential.

Green synthesis of nanoparticles provides numerous advantages over physical and chemical methods because of low toxicity, high yields, cost-effectiveness, environmentally benign, and energy efficiency. Therefore, we focused on the facile and green synthesis of isotropic silver nanoparticles using the metabolic extract of Cytobacillus kochii. During synthesis, the physicochemical parameters were optimized and validated using the response surface methodology statistical tool. The presence of potent bioactive compounds that aid in the biofabrication of nanoparticles was identified in the gas chromatography-mass spectroscopy analysis and the synthesis was confirmed by surface plasmon resonance peak at 420 nm. Characterization of nanoparticles was performed by high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and X-ray diffraction. The synthesized nanoparticles showed potent antioxidant properties and displayed an excellent catalytic reduction potential in the degradation of hazardous dyes, such as methylene blue, phenol red, and 4-nitrophenol. Furthermore, compared to the chemically synthesized silver nanoparticles and crude extract, the biogenic silver nanoparticles exhibited a broad-spectrum antimicrobial potential. Our results demonstrate that the reported silver nanoparticles with unique characteristics might be of great promise as biomedical and catalytic agents for industrial applications.

Multicomponent Self-Assembly of Diaminobenzoquinonato-Bridged Manganese(I) Metallosupramolecular Rectangles: Host-Guest Interactions, Anticancer Activity, and Visible-Light-Induced CO Releasing Studies.

The one-pot self-assembly of Mn2(CO)10, a bis-chelated diaminobenzoquinonato (ON∩ON) bridge (L), and a linear ditopic linker (N∩N) (L') has resulted into the formation of M4L2L2'-type manganese(I)-based tetranuclear metallorectangles of the general formula [{(CO)3Mn(µ-η4-L)Mn(CO)3}2(µ-(N-N)2)] (1-8), wherein L is 2,5-bis(n-butylamine)-1,4-benzoquinone (bbbq) and/or 2,5-bis(phenethylamino)-1,4-benzoquinone (bpbq) and N-N is 4,4'-bipyridine (bpy), trans-1,2-bis(4-pyridyl) ethylene (bpe), phenyl-1,4-bis(isonicotinate) (pbin), and N,N'-bis(4-pyridylformamide)-1,4-benzene (bpfb). Metallorectangles 1-8 were characterized by infrared, ultraviolet-visible (UV-vis) absorption, and 1H nuclear magnetic resonance spectroscopies, elemental analysis, and electrospray ionization-mass spectrometry. The molecular and crystal structures of 1•n(CHCl3) and coronene⊂3•coronene were determined by the single-crystal X-ray diffraction method. Host-guest binding abilities of 1, 3, and 7 with coronene, pyrene, and 4,4'-dihydroxybiphenyl were investigated using UV-vis absorption and emission spectroscopic techniques. Formation of host-guest complexes was further confirmed by the single-crystal X-ray structural analysis. Absorption of spectra of these metallorectangles showed high-intensity metal-ligand charge transfer as a broad band in the visible region. In vitro cytotoxicity assays were performed on 1, 3, 5, and 7 against lung, colon, and cervical cancer cells as well as normal cells. Compounds 5 and 7 were identified as visible-light-induced CO-releasing molecules from the myoglobin assay.

Self-Assembled Manganese(I)-Based Selenolato-Bridged Tetranuclear Metallorectangles: Host-Guest Interaction, Anticancer, and CO-Releasing Studies.

Supramolecular one-step self-assembly of dimanganese decacarbonyl, diaryl diselenide, and linear dipyridyl ligands (L = pyrazine (pz), 4,4'-bipyridine (bpy), and trans-1,2-bis(4-pyridyl)ethylene (bpe)) has resulted in the formation of selenolato-bridged manganese(I)-based metallorectangles. The synthesis of tetranuclear Mn(I)-based metallorectangles [{(CO)3Mn(µ-SeR)2Mn(CO)3}2(µ-L)2] (1-6) was facilitated by the oxidative addition of diaryl diselenide to dimanganese decacarbonyl with the simultaneous coordination of linear bidentate pyridyl linker in an orthogonal fashion. Formation of metallorectangles 1-6 was ascertained using IR, UV-vis, NMR spectroscopic techniques, and elemental analyses. The molecular mass of compounds 2, 4, and 6 were determined by ESI-mass spectrometry. Solid-state structural elucidation of 2, 3, and 6 by single-crystal X-ray diffraction methods revealed a rectangular framework wherein selenolato-bridges and pyridyl ligands define the shorter and longer edges, respectively. Also, the guest binding capability of metallorectangles 3 and 5 with different aromatic guests was studied using UV-vis absorption and emission spectrophotometric titration methods that affirmed strong host-guest binding interactions. The formation of the host-guest complex between metallorectangle 3 and pyrene has been explicitly corroborated by the single-crystal X-ray structure of 3•pyrene. Moreover, select metallorectangles 1-4 and 6 were studied to explore their anticancer activity, while CO-releasing ability of metallorectangle 2 was further appraised using equine heart myoglobin assay.

Molecular interaction of manganese based carbon monoxide releasing molecule (MnCORM) with human serum albumin (HSA).

In the present study, the interaction between the HSA and MnCORM in vitro under physiological conditions, was investigated through ultraviolet-visible (UV-vis) absorption, fluorescence, time-resolved fluorescence, circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopic techniques and in silico molecular docking methods. Binding parameters such as the binding constant, number of binding sites and binding force were obtained from the fluorescence data. Thermodynamic interaction revealed that the reaction was spontaneous (ΔG < 0) and hydrogen bond and van der Waals interaction were primarily involved in the binding. The changes induced in the secondary structure conformation due to the MnCORM interaction were monitored using CD and FT-IR spectroscopic techniques. The results showed reduction in α-helix conformation and corresponding increase in ß-sheet and unordered structures due to slight unfolding. The time-resolved fluorescence decay confirmed the static quenching mechanism of the MnCORM. The molecular docking studies revealed that the MnCORM interacted at Sudlow's site II of domain IIIA through hydrogen bond and van der Waals interactions. In order to understand the drug distribution and elimination, studies on the drug molecule interaction with HSA are vital. Therefore, it is evident that MnCORM interacts with HSA through ground state complex formation and thus suitable for in vivo delivery.

Single-Pot Self-Assembly of Heteroleptic Mn(I)-Based Aminoquinonato-Bridged Ester/Amide-Functionalized Dinuclear Metallastirrups: Potential Anticancer and Visible-Light-Triggered CORMs.

Multicomponent self-assembly of Mn2(CO)10, a bis-chelating aminoquinonato (ON∩ON) bridge (L), and an ester/amide-functionalized flexible neutral ditopic linker (L') has resulted into the formation of M2LL'-type manganese(I)-based dinuclear metallastirrups of general formula [{(CO)3Mn(µ-η4-L)Mn(CO)3}(µ-L')] (1-10). Compounds 1-10 were accomplished via orthogonal bonding of the aminoquinone ligand (2,5-bis(n-butylamino)-1,4-benzoquinone/2,5-bis(phenethylamino)-1,4-benzoquinone) and ditopic pyridyl ligand to manganese carbonyl. The resultant metallastirrups were characterized using elemental analyses and IR, UV-vis, 1H NMR, and electrospray ionization-mass spectroscopic techniques. The molecular structure of 6 was confirmed by single-crystal X-ray diffraction methods. Furthermore, molecular recognition capabilities of 1, 5, 7, and 9 were evaluated with aromatic compounds containing hydroxy/amine functionalities. Anticancer activities of compounds 1-3, 5-7, 9, and 10 were investigated against three cancer cell lines, that is, lung (A549), colon (HCT-15), and cervical (HeLa) as well as on normal cells (HEK 293). Compound 9 showed a broad-spectrum inhibition toward these cancer cells upon exposure to visible light. The myoglobin assay was performed using UV-vis absorption spectroscopy to investigate the visible-light-triggered CO release from 5 and 9 that could be related to their ability to effectively inhibit cancer cells. In addition, morphological studies confirmed the induction of autophagy due to the treatment of cancer cells using compound 9.

A novel guaiane sesquiterpene derivative, guai-2-en-10α-ol, from Ulva fasciata Delile inhibits EGFR/PI3K/Akt signaling and induces cytotoxicity in triple-negative breast cancer cells.

A novel guaiane sesquiterpene derivative, guai-2-en-10α-ol, from Ulva fasciata Delile exhibits antimicrobial property. U. fasciata extract was reported to exhibit cytotoxicity against cancer. In the present study, we have studied the anticancer potential of the compound, guai-2-en-10α-ol, from U. fasciata. The compound showed selective cytotoxicity toward triple-negative breast cancer (TNBC) cell line (MDA MB-231) in a dose-dependent manner. In treated cells, the apoptotic hallmarks such as formation of apoptotic bodies, cell shrinkage, and nuclear condensation were observed. Many small molecules affect the function of cellular signaling pathways. As EGFR/PI3K/Akt pathway proteins are frequently altered in TNBC, we have studied the gene expression of key proteins of this pathway. The semiquantitative PCR results demonstrated the down-regulated expression of PDPK1 (positive regulator) and Akt (key activator) as well as up-regulated expression of PTEN (negative regulator), which suggested the interaction of guai-2-en-10α-ol with upstream protein. Further investigation showed the down-regulation of both PI3K and EGFR. As EGFR is the most upstream protein of the pathway, its protein level expression was investigated. Western blotting analysis confirmed the down-regulation of p-EGFR expression and activation of apoptosis upon compound treatment. Cell cycle analysis also evidenced the G1 phase arrest, which can be due to the inhibition of cell survival pathway. Computational studies showed the interaction of guai-2-en-10α-ol with Asp855 residue of EGFR kinase domain in active conformation. All these results demonstrate the anticancer potential of guai-2-en-10α-ol through EGFR/PI3K/Akt pathway.

Physico-cultural parameters during AgNPs biotransformation with bactericidal activity against human pathogens.

Production of AgNPs with desired morphologies and surface characteristics using facile, economic and non-laborious processes is highly imperative. Cell extract based syntheses are emerging as a novel technique for the production of diverse forms of NPs, and is assured to meet the requirements. Therefore, in order to have a better understanding, and to improvise and gain control over the NPs morphological and surface characteristics, the present investigation systematically evaluates the influence of various major physico-cultural parameters including diverse growth media, concentrations of precursor salts; pH and temperature on the biotransformation of ionic silver (Ag+) to nanopariculate silver nanoparticles (AgNPs), utilizing the cell free extract of the bacterium, P. plecoglossicida. The synthesis, purity, morphology and surface characteristics of the AgNPs during optimization studies were measured. The bactericidal effect of these AgNPs was assessed using multi-drug resistant human pathogens; Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica based on the diameter of inhibition zone in disk diffusion tests. The nanoparticles were found to be of higher toxicity to E. coli and S. enterica than A. baumannii and P. aeruginosa. The results demonstrate that the chosen parameters in whole or in part could have a significant influence on the morphology, surface characteristics, duration of production, overall yield and production of AgNPs.

In vitro antiproliferative, pro-apoptotic, antimetastatic and anti-inflammatory potential of 2,4-diacetylphloroglucinol (DAPG) by Pseudomonas aeruginosa strain FP10.

The 2,4-diacetylphloroglucinol (DAPG), a polyketide metabolite extracted from Pseudomonas aeruginosa strain FP10, exhibited selective cytoxicity against lung (A549), breast (MDA MB-231), cervical (HeLa) and colon (HCT-15) cancer cells in differential and dose-dependent manner. The anticancer and antimetastatic activities of DAPG were mediated by the inhibition of ROS, NF-κB, Bcl-2, MMP-2, VEGF and primary inflammatory mediators such as TNF-α, IL-6, IL-1ß and NO. The DAPG induced apoptosis in cancer cells by intrinsic and extrinsic pathways via the release of cytochrome-C, upregulation of Bax and the activation of caspases and also, exhibited anti-inflammatory activity by the inhibition of LPS-inflammed cell proliferation of macrophage (Raw 264.7), monocytic cells (THP-1) and peripheral blood mononuclear cells (PBMCs). Results further confirmed that the DAPG inhibited the primary inflammatory mediators in cancer cells and inflammed immune cells through the down regulation of NF-κB. In the present study, for the first time, antiproliferative, proapoptotic, antimetastatic and anti-inflammatory activities of DAPG in various cancer cells and inflammation-induced immune cells have been reported.

Draft Genome Sequence of a Novel Nicotine-Degrading Bacterium, Pseudomonas plecoglossicida TND35.

Pseudomonas plecoglossicida TND35 is a potent nicotine-degrading bacterium. The draft genome sequence of strain TND35 contains 6,209,227 bp, 5,511 coding genes, and a G+C content of 62.3%. It encompasses genes related to catabolism of nicotine, N-heterocyclic aromatic compounds, heavy metal degradation, and butanol biosynthesis.

Green Chemistry Approach for the Synthesis of Gold Nanoparticles Using the Fungus Alternaria sp.

The synthesis of gold nanoparticles has gained tremendous attention owing to their immense applications in the field of biomedical sciences. Although several chemical procedures are used for the synthesis of nanoparticles, the release of toxic and hazardous by-products restricts their use in biomedical applications. In the present investigation, gold nanoparticles were synthesized biologically using the culture filtrate of the filamentous fungus Alternaria sp. The culture filtrate of the fungus was exposed to three different concentrations of chloroaurate ions. In all cases, the gold ions were reduced to Au(0), leading to the formation of stable gold nanoparticles of variable sizes and shapes. UV-Vis spectroscopy analysis confirmed the formation of nanoparticles by reduction of Au(3+) to Au(0). TEM analysis revealed the presence of spherical, rod, square, pentagonal, and hexagonal morphologies for 1 mM chloroaurate solution. However, quasi-spherical and spherical nanoparticles/heart-like morphologies with size range of about 7-13 and 15-18 nm were observed for lower molar concentrations of 0.3 and 0.5 mM gold chloride solution, respectively. The XRD spectrum revealed the face-centered cubic crystals of synthesized gold nanoparticles. FT-IR spectroscopy analysis confirmed the presence of aromatic primary amines, and the additional SPR bands at 290 and 230 nm further suggested that the presence of amino acids such as tryptophan/tyrosine or phenylalanine acts as the capping agent on the synthesized mycogenic gold nanoparticles.

Biodegradation of nicotine by a novel nicotine-degrading bacterium, Pseudomonas plecoglossicida TND35 and its new biotransformation intermediates.

Tobacco wastes that contain nicotine alkaloids are harmful to human health and the environment. In the investigation, a novel nicotine-biodegrading bacterium TND35 was isolated and identified as Pseudomonas plecoglossicida on the basis of phenotypic, biochemical characteristics and 16S rRNA sequence homology. We have studied the nicotine biodegradation potential of strain TND35 by detecting the intermediate metabolites using an array of approaches such as HPLC, GC-MS, NMR and FT-IR. Biotransformation metabolites, N-methylmyosmine, 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) and other three new intermediate metabolites namely, 3,5-bis (1-methylpyrrolidin-2-yl) pyridine, 2,3-dihydro-1-methyl-5-(pyridin-3-yl)-1H-pyrrol-2-ol and 5-(pyridin-3-yl)-1H-pyrrol-2(3H)-one have been identified. Interestingly, these intermediate metabolites suggest that the strain TND35 employs a novel nicotine biodegradation pathway, which is different from the reported pathways of Aspergillus oryzae 112822, Arthrobacter nicotinovorans pAO1, Agrobacterium tumefaciens S33 and other species of Pseudomonas. The metabolite, HPB reported in this study can also be used as biochemical marker for tobacco related cancer studies.

Extracellular synthesis of mycogenic silver nanoparticles by Cylindrocladium floridanum and its homogeneous catalytic degradation of 4-nitrophenol.

Green synthesis of extracellular mycogenic silver nanoparticles using the fungus, Cylindrocladium floridanum is reported. The synthesized mycogenic silver nanoparticles were characterized using UV-Vis absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. The nanoparticles exhibit fcc structure with Bragg's reflections of (111), (200), (220) and (311) was evidenced by XRD pattern, high-resolution TEM lattice fringes and circular rings in selected-area electron diffraction (SAED) pattern. The morphology of nanoparticles was roughly spherical in shape with an average size of ca. 25 nm. From FTIR spectrum, it was found that the biomolecules with amide I and II band were involved in the stabilization of nanoparticles. These mycogenic silver nanoparticles exhibited the homogeneous catalytic potential in the reduction of pollutant, 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using sodium borohydride, which followed a pseudo-first-order kinetic model. Thus, the synthesis of metal nanoparticles using sustainable microbial approach opens up possibilities in the usage of mycogenic metal nanoparticles as catalysts in various chemical reactions.

Mycocrystallization of gold ions by the fungus Cylindrocladium floridanum.

The size and morphology determines the thermodynamic, physical and electronic properties of metal nanoparticles. The extracellular synthesis of gold nanoparticles by fungus, Cylindrocladium floridanum, which acts as a source of reducing and stabilizing agent has been described. The synthesized nanoparticles were characterized using techniques such as UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis (EDAX), and high-resolution transmission electron microscopy (HR-TEM). Based on the evidence of HR-TEM, the synthesized particles were found to be spherical with an average size of 19.05 nm. Powder XRD pattern proved the formation of (111)-oriented face-centered cubic crystals of metallic gold. This microbial approach by fungus for the green synthesis of spherical gold nanoparticles has many advantages such as economic viability, scaling up and environment friendliness.

Biosynthesis of silver nanoparticles by phytopathogen Xanthomonas oryzae pv. oryzae strain BXO8.

Extracellular biogenic synthesis of silver nanoparticles with various shapes using the rice bacterial blight bacterium Xanthomonas oryzae pv. oryzae BXO8 is reported. The synthesized silver nanoparticles were characterized by UV-Vis spectroscopy, powder X-ray diffractometry (XRD), scanning electron microscopy, energy dispersive X-ray spectrometry, and highresolution transmission electron microscopy (HR-TEM). Based on the evidence of HR-TEM, the synthesized particles were found to be spherical, with anisotropic structures such as triangles and rods, with an average size of 14.86 nm. The crystalline nature of silver nanoparticles was evident from the bright circular spots in the SAED pattern, clear lattice fringes in the high-resolution TEM images, and peaks in the XRD pattern. The FTIR spectrum showed that biomolecules containing amide and carboxylate groups are involved in the reduction and stabilization of the silver nanoparticles. Using such a biological method for the synthesis of silver nanoparticles is a simple, viable, cost-effective, and environmentally friendly process, which can be used in antimicrobial therapy.

Transgenic expression of plant chitinases to enhance disease resistance.

Crop plants have evolved an array of mechanisms to counter biotic and abiotic stresses. Many pathogenesis-related proteins are expressed by plants during the attack of pathogens. Advances in recombinant DNA technology and understanding of plant-microbe interactions at the molecular level have paved the way for isolation and characterization of genes encoding such proteins, including chitinases. Chitinases are included in families 18 and 19 of glycosyl hydrolases (according to www.cazy.org ) and they are further categorized into seven major classes based on their aminoacid sequence homology, three-dimensional structures, and hydrolytic mechanisms of catalytic reactions. Although chitin is not a component of plant cell walls, plant chitinases are involved in development and non-specific stress responses. Also, chitinase genes sourced from plants have been successfully over-expressed in crop plants to combat fungal pathogens. Crops such as tomato, potato, maize, groundnut, mustard, finger millet, cotton, lychee, banana, grape, wheat and rice have been successfully engineered for fungal resistance either with chitinase alone or in combination with other PR proteins.

Purification and characterization of a thermophilic cellulase from a novel cellulolytic strain, Paenibacillus barcinonensis.

A novel bacterial strain, MG7, with high cellulase activity was isolated and identified by morphological characteristics and molecular phylogeny analysis as Paenibacillus barcinonensis. Maximum production of cellulase by MG7 was observed at pH 7.0 and 35°C. The enzyme was purified with a specific activity of 16.88 U/mg, the cellulase activity was observed in a zymogram, and its molecular mass (58.6 kDa) was confirmed by SDS-PAGE. The purified enzyme showed maximum activity at pH 6.0 and 65°C and degraded cellulosic substrates such as carboxy methyl cellulose (CMC), Avicel, filter paper, and beta-glucan. The enzyme showed stability with 0.5% concentration of various surfactants. The K(m) and V(max) of cellulase for CMC and Avicel were found to be 0.459 mg/ml and 10.46 mg/ml/h, and 1.01 mg/ml and 10.0 mg/ml/h, respectively. The high catalytic activity and its stability to temperature, pH, surfactants, and metal ions indicated that the cellulase enzyme by MG7 is a good candidate for biotechnological applications.

Plant ß-1,3-glucanases: their biological functions and transgenic expression against phytopathogenic fungi.

ß-1,3-Glucanases are abundant in plants and have been characterized from a wide range of species. They play key roles in cell division, trafficking of materials through plasmodesmata, in withstanding abiotic stresses and are involved in flower formation through to seed maturation. They also defend plants against fungal pathogens either alone or in association with chitinases and other antifungal proteins. They are grouped in the PR-2 family of pathogenesis-related (PR) proteins. Use of ß-1,3-glucanase genes as transgenes in combination with other antifungal genes is a plausible strategy to develop durable resistance in crop plants against fungal pathogens. These genes, sourced from alfalfa, barley, soybean, tobacco, and wheat have been co-expressed along with other antifungal proteins, such as chitinases, peroxidases, thaumatin-like proteins and α-1-purothionin, in various crop plants with promising results that are discussed in this review.

Microbial diversity of vermicompost bacteria that exhibit useful agricultural traits and waste management potential.

Vermicomposting is a non-thermophilic, boioxidative process that involves earthworms and associated microbes. This biological organic waste decomposition process yields the biofertilizer namely the vermicompost. Vermicompost is a finely divided, peat like material with high porosity, good aeration, drainage, water holding capacity, microbial activity, excellent nutrient status and buffering capacity thereby resulting the required physiochemical characters congenial for soil fertility and plant growth. Vermicompost enhances soil biodiversity by promoting the beneficial microbes which inturn enhances plant growth directly by production of plant growth-regulating hormones and enzymes and indirectly by controlling plant pathogens, nematodes and other pests, thereby enhancing plant health and minimizing the yield loss. Due to its innate biological, biochemical and physiochemical properties, vermicompost may be used to promote sustainable agriculture and also for the safe management of agricultural, industrial, domestic and hospital wastes which may otherwise pose serious threat to life and environment.

Assessment of Microbial Richness in Pelagic Sediment of Andaman Sea by Bacterial Tag Encoded FLX Titanium Amplicon Pyrosequencing (bTEFAP).

Microbial diversity of 1,000 m deep pelagic sediment from off Coast of Andaman Sea was analyzed by a culture independent technique, bacterial tag encoded FLX titanium amplicon pyrosequencing. The hypervariable region of small subunit ribosomal rRNA gene covering V6-V9, was amplified from the metagenomic DNA and sequenced. We obtained 19,271 reads, of which 18,206 high quality sequences were subjected to diversity analysis. A total of 305 operational taxonomic units (OTUs) were obtained corresponding to the members of firmicutes, proteobacteria, plantomycetes, actinobacteria, chloroflexi, bacteroidetes, and verucomicrobium. Firmicutes was the predominant phylum, which was largely represented with the family bacillaceae. More than 44 % of sequence reads could not be classified up to the species level and more than 14 % of the reads could not be assigned to any genus. Thus, the data indicates the possibility for the presence of uncultivable or unidentified novel bacterial species. In addition, the community structure identified in this study significantly differs with other reports from marine sediments.

Green synthesis of biogenic metal nanoparticles by terrestrial and aquatic phototrophic and heterotrophic eukaryotes and biocompatible agents.

The size, shape and controlled dispersity of nanoparticles play a vital role in determining the physical, chemical, optical and electronic properties attributing its applications in environmental, biotechnological and biomedical fields. Various physical and chemical processes have been exploited in the synthesis of several inorganic metal nanoparticles by wet and dry approaches viz., ultraviolet irradiation, aerosol technologies, lithography, laser ablation, ultrasonic fields, and photochemical reduction techniques. However, these methodologies remain expensive and involve the use of hazardous chemicals. Therefore, there is a growing concern for the development of alternative environment friendly and sustainable methods. Increasing awareness towards green chemistry and biological processes has led to a necessity to develop simple, cost-effective and eco-friendly procedures. Phototrophic eukaryotes such as plants, algae, and diatoms and heterotrophic human cell lines and some biocompatible agents have been reported to synthesize greener nanoparticles like cobalt, copper, silver, gold, bimetallic alloys, silica, palladium, platinum, iridium, magnetite and quantum dots. Owing to the diversity and sustainability, the use of phototrophic and heterotrophic eukaryotes and biocompatible agents for the synthesis of nanomaterials is yet to be fully explored. This review describes the recent advancements in the green synthesis and applications of metal nanoparticles by plants, aquatic autotrophs, human cell lines, biocompatible agents and biomolecules.