Use of marine microorganisms in designing anti-infective strategies for sustainable aquaculture production.

Aquaculture, a noteworthy food production sector, is confronted with disease occurrences. Treatment of aquaculture pathogens with antibiotics is often rendered ineffective due to biofilm formation and the development of resistant strains. Marine ecosystems encompass unusual microorganisms that produce novel bioactive compounds, including agents that could be used as alternatives to antibiotics. Moreover, biomass and/or biomolecules associated with these microorganisms could act as feed supplements to enhance the overall health of aquaculture species' and improve water quality parameters. The present review summarizes the contents of studies on such marine microorganisms with the potential to be developed as agents for tackling bacterial diseases in the aquaculture segment. Bioactive compounds produced by marine bacteria are known to inhibit biofilm-associated infections mediated by their bactericidal properties (produced by Bacillus, Vibrio, Photobacterium, and Pseudoalteromonas species), surfactant activity (obtained from different species of Bacillus and Staphylococcus lentus), anti-adhesive activity (derived from Bacillus sp. and Brevibacterium sp.), and quorum sensing inhibition. Several marine fungal isolates capable of producing antibacterial agents have also been effective in inhibiting aquaculture-associated pathogens. Another strategy followed by investigators to reduce the severity of infections is the use of bacterial, yeast, and microalgae biomass as feed supplements, probiotics, and immunostimulants. In some cases, marine microalgae have been employed as sustainable alternatives to fish oil and fish meal without compromising on nutritional quality. Their inclusion in aquaculture feed has enhanced growth, favored better survival of cultured species, and improved water quality parameters. Marine microorganisms (by providing effective bioactive compounds and being used as feed supplements) could enable aquaculture practices to be more sustainable in the future.

Assessment of recombinant glutathione-S-transferase (HaGST-8) silica nano-conjugates for effective removal of pesticides.

Diverse glutathione-S-transferases (GSTs) are produced by insect pests including Helicoverpa armigera (HaGSTs) for detoxification of insecticides or xenobiotic compounds that they encounter. In an earlier study, the HaGST-8 gene was isolated from H. armigera larvae exposed to pesticide mixtures and the recombinant protein was expressed in the yeast Pichia pastoris. In this investigation, HaGST-8 was successfully immobilized on glutaraldehyde-activated APTES functionalized silica nanoparticles to obtain SiAPT-HaGST-8 nano-conjugates. Although enzyme activity associated with these conjugates was comparable to that of free HaGST-8, the specific activity of the former was found to be 1.25 times higher than the latter. In comparison with the free enzyme (that demonstrated a pH optimum of 9.0), for the nano-conjugates, the pH range was extended between pH 8.0 to 9.0. The optimum temperature for activity of both forms of the enzyme was found to be 30 °C. Stability of the enzyme was improved from 20 d for free HaGST-8 to 30 d for SiAPT-HaGST-8 nano-conjugates. Some loss in GST activity was detected after every reuse cycle of nano-conjugates and in all, 63% reduction was observed after three cycles. When 3 kinds of pesticides (namely, chlorpyrifos, dichlorvos and cypermethrin) were reacted with SiAPT-HaGST-8, more than 80% reduction in levels were observed. On the basis of the results obtained, the use of such silica nanoparticle-based systems for stable enzyme conjugation followed by effective removal of pesticides from aqueous media is envisaged.

Transcriptome Response of the Tropical Marine Yeast Yarrowia lipolytica on Exposure to Uranium.

In our earlier investigation, we reported the consequences of uranium (U)-induced oxidative stress and cellular defense mechanisms alleviating uranium toxicity in the marine yeast Yarrowia lipolytica NCIM 3589. However, there is lack of information on stress response towards uranium toxicity at molecular level in this organism. To gain an insight on this, transcriptional response of Y. lipolytica after exposure to 50 µM uranium was investigated by RNA sequencing at the global level in this study. The de novo transcriptome analysis (in triplicates) revealed 56 differentially expressed genes with significant up-regulation and down-regulation of 33 and 23 transcripts, respectively, in U-exposed yeast cells as compared to the control, U-unexposed cells. Highly up-regulated genes under U-treated condition were identified to be primarily involved in transport, DNA damage repair and oxidative stress. The major reaction of Y. lipolytica to uranium exposure was the activation of oxidative stress response mechanisms to protect the important biomolecules of the cells. On the other hand, genes involved in cell wall and cell cycle regulation were significantly down-regulated. Overall, the transcriptional profiling by RNA sequencing to stress-inducing concentration of uranium sheds light on the various responses of Y. lipolytica for coping with uranium toxicity, providing a foundation for understanding the molecular interactions between uranium and this marine yeast.

Layer-by-Layer Assembled Nanostructured Lipid Carriers for CD-44 Receptor-Based Targeting in HIV-Infected Macrophages for Efficient HIV-1 Inhibition.

Macrophages act as a cellular reservoir in HIV infection. Elimination of HIV from macrophages has been an unfulfilled dream due to the failure of drugs to reach them. To address this, we developed CD44 receptor-targeted, novel hyaluronic acid (HA)-coated nanostructured lipid carriers (NLCs) of efavirenz via washless layer-by-layer (LbL) assembly of HA and polyallylamine hydrochloride (PAH). NLCs were subjected to TEM analysis, size and zeta potential, in vitro release and encapsulation efficiency studies. The uptake of NLCs in THP-1 cells was studied using fluorescence microscopy and flow cytometry. The anti-HIV efficacy was evaluated using p24 antigen inhibition assay. NLCs were found to be spherical in shape with anionic zeta potential (-23.66 ± 0.87 mV) and 241.83 ± 5.38 nm particle size. NLCs exhibited prolonged release of efavirenz during in vitro drug release studies. Flow cytometry revealed 1.73-fold higher uptake of HA-coated NLCs in THP-1 cells. Cytotoxicity studies showed no significant change in cell viability in presence of NLCs as compared with the control. HA-coated NLCs distributed throughout the cell including cytoplasm, plasma membrane and nucleus, as observed during fluorescence microscopy. HA-coated NLCs demonstrated consistent and significantly higher inhibition (81.26 ± 1.70%) of p24 antigen which was 2.08-fold higher than plain NLCs. The obtained results suggested preferential uptake of HA-coated NLCs via CD44-mediated uptake. The present finding demonstrates that HA-based CD44 receptor targeting in HIV infection is an attractive strategy for maximising the drug delivery to macrophages and achieve effective viral inhibition.

Gold nanoparticles biosynthesized by Nocardiopsis dassonvillei NCIM 5124 enhance osteogenesis in gingival mesenchymal stem cells.

Gold nanoparticles are widely used for biomedical applications owing to their biocompatibility, ease of functionalization and relatively non-toxic nature. In recent years, biogenic nanoparticles have gained attention as an eco-friendly alternative for a variety of applications. In this report, we have synthesized and characterized gold nanoparticles (AuNPs) from an Actinomycete, Nocardiopsis dassonvillei NCIM 5124. The conditions for biosynthesis were optimized (100 mg/ml of cell biomass, 2.5 mM tetrachloroauric acid (HAuCl4) at 80 °C and incubation time of 25 min) and the nanoparticles were characterized by TEM, SAED, EDS and XRD analysis. The nanoparticles were spherical and ranged in size from 10 to 25 nm. Their interactions with human gingival tissue-derived mesenchymal stem cells (GMSCs) and their potential applications in regenerative medicine were evaluated further. The AuNPs did not display cytotoxicity towards GMSCs when assessed by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay, DNA fragmentation patterns and Annexin V/propidium iodide staining techniques. These AuNPs induced faster cell migration when monitored by the in vitro wound healing assay. The effect of these nanoparticles on osteogenesis of GMSCs was also studied. Based on the results obtained from alkaline phosphatase, Von Kossa staining and Alizarin Red S staining, the AuNPs were seen to positively affect differentiation of GMSCs and enhance mineralization of the synthesized matrix. We therefore conclude that the biogenic, non-toxic AuNPs are of potential relevance for tissue regeneration applications.

An insight into the ecology, diversity and adaptations of Gordonia species.

The bacterial genus Gordonia encompasses a variety of versatile species that have been isolated from a multitude of environments. Gordonia was described as a genus about 20 years ago, and to date, 39 different species have been identified. Gordonia is recognized for symbiotic associations with multiple hosts, including aquatic (marine and fresh water) biological forms and terrestrial invertebrates. Some Gordonia species isolated from clinical specimens are known to be opportunistic human pathogens causing secondary infections in immunocompromised and immunosuppressive individuals. They are also predominant in mangrove ecosystems and terrestrial sites. Members of the genus Gordonia are ecologically adaptable and show marked variations in their properties and products. They generate diverse bioactive compounds and produce a variety of extracellular enzymes. In addition, production of surface active compounds and carotenoid pigments allows this group of microorganisms to grow under different conditions. Several isolates from water and soil have been implicated in bioremediation of different environments and plant associated species have been explored for agricultural applications. This review highlights the prevalence of the members of this versatile genus in diverse environments, details its associations with living forms, summarizes the biotechnologically relevant products that can be obtained and discusses the salient genomic features that allow this Actinomycete to survive in different ecological niches.

Efficacy of cell free supernatant from Bacillus licheniformis in protecting Artemia salina against Vibrio alginolyticus and Pseudomonas gessardii.

Bacterial diseases are widespread in aquaculture farms and causative agents often adapt to biofilm mode of growth. These biofilms are detrimental to aquaculture species as they resist antibiotics and other agents that are used to control them. Two bacterial pathogens isolated from infected prawn samples were identified as Vibrio alginolyticus and Pseudomonas gessardii on the basis of morphological features, biochemical characteristics, 16S r RNA gene sequencing and phylogenetic analysis. Their pathogenic nature was confirmed by performing in vivo challenge experiments using Artemia salina as a model system. Seven days post infection, the mortality observed with V. alginolyticus and P. gessardii was 97 ±â€¯4.08% and 77.5 ±â€¯5.24%, respectively. The isolates formed extensive biofilms on polystyrene and glass surfaces. These infections could be controlled in an effective manner by using the cell free supernatant (CFS) of a tropical marine epizoic strain of Bacillus licheniformis D1 that is earlier reported to contain an antimicrobial protein (BLDZ1). The CFS inhibited biofilms in an efficient manner (82.35 ±â€¯1.69 and 82.52 ±â€¯1.11% for V. alginolyticus and P. gessardii, respectively) on co-incubation. In addition, pre-formed biofilms of V. alginolyticus and P. gessardii were also removed (84.53 ±â€¯1.26 and 67.08 ±â€¯1.43%, respectively). Fluorescence and scanning electron microscopic studies confirmed the antibiofilm potential of this protein on glass surfaces. The antibiofilm nature was due to the anti-adhesion and antimicrobial properties exhibited by the CFS. Treatment of A. salina with CFS (6 h prior to infections) was effective in protecting larvae against infections by field isolates. This study highlights the significance of marine natural products in providing alternative biofilm controlling agents to tackle infections and decreasing the usage of antibiotics in aquaculture settings.

Heavy metal tolerance in marine strains of Yarrowia lipolytica.

Heavy metal tolerance of two marine strains of Yarrowia lipolytica was tested on solid yeast extract peptone dextrose agar plates. Based on minimum inhibitory concentration esteems, it is inferred that the two strains of Y. lipolytica were tolerant to heavy metals such as Pb(II), Cr(III), Zn(II), Cu(II), As(V), and Ni(II) ions. The impact of various heavy metal concentrations on the growth kinetics of Y. lipolytica was likewise assessed. With increased heavy metal concentration, the specific growth rate was reduced with delayed doubling time. Furthermore, biofilm development of both yeasts on the glass surfaces and in microtitre plates was assessed in presence of different heavy metals. In microtitre plates, a short lag phase of biofilm formation was noticed without the addition of heavy metals in yeast nitrogen base liquid media. A lag phase was extended over increasing metal concentrations of media. Heavy metals like Cr(VI), Cd(II), and As(V) are contrastingly influenced on biofilms' formation of microtitre plates. Other heavy metals did not much influence on biofilms development. Thus, biofilm formation is a strategy of Y. lipolytica under stress of heavy metals has significance in bioremediation process for recovery of heavy metals from contaminated environment.

Morphological response of Yarrowia lipolytica under stress of heavy metals.

The marine dimorphic yeast Yarrowia lipolytica has been proposed as a suitable model for the dimorphism study. In this study, the morphological behaviour of two marine strains of Y. lipolytica (NCIM 3589 and NCIM 3590) was studied under stress of different heavy metals. Scanning electron microscopy was used to investigate the morphological features of yeast cells. This study revealed that the normal ellipsoidal shape of yeast cells was changed into oval, rounded, or elongated in response to different heavy-metal stress. Light microscopy was also used to investigate individual properties of yeast cells. The average cell length and radius of both marine strains was increased with increasing concentrations of heavy-metal ions. In addition, the elongation factor was calculated and was increased in the presence of heavy metals like Pb(II), Co(II), Cr(III), Cr(VI), and Zn(II) under the static conditions.

Metals in mangrove ecosystems and associated biota: A global perspective.

Mangrove forests prevalent along the intertidal regions of tropical and sub-tropical coastlines are inimitable and dynamic ecosystems. They protect and stabilize coastal areas from deleterious consequences of natural disasters such as hurricanes and tsunamis. Although there are reviews on ecological aspects, industrial uses of mangrove-associated microorganisms and occurrence of pollutants in a region-specific manner, there is no exclusive review detailing the incidence of metals in mangrove sediments and associated biota in these ecosystems on a global level. In this review, mangrove forests have been classified in a continent-wise manner. Most of the investigations detail the distribution of metals such as zinc, chromium, arsenic, copper, cobalt, manganese, nickel, lead and mercury although in some cases levels of vanadium, strontium, zirconium and uranium have also been studied. Seasonal, tidal, marine, riverine, and terrestrial components are seen to influence occurrence, speciation, bioavailability and fate of metals in these ecosystems. In most of the cases, associated plants and animals also accumulate metals to different extents and are of ecotoxicological relevance. Levels of metals vary in a region specific manner and there is disparity in the pollution status of different mangrove areas. Protecting these vulnerable ecosystems from metal pollutants is important from environmental safety point of view.

Role of induced glutathione-S-transferase from Helicoverpa armigera (Lepidoptera: Noctuidae) HaGST-8 in detoxification of pesticides.

The present study deals with glutathione-S-transferase (GST) based detoxification of pesticides in Helicoverpa armigera and its potential application in eliminating pesticides from the environment. Dietary exposure of a pesticide mixture (organophosphates - chlorpyrifos and dichlorvos, pyrethroid - cypermethrin; 2-15ppm each) to H. armigera larvae resulted in a dose dependant up-regulation of GST activity and gene expression. A variant GST from H. armigera (HaGST-8) was isolated from larvae fed with 10ppm pesticide mixture and it was recombinantly expressed in yeast (Pichia pastoris HaGST-8). HaGST-8 had a molecular mass of 29kDa and was most active at pH 9 at 30°C. GC-MS and LC-HRMS analysis validated that HaGST-8 was effective in eliminating organophosphate type of pesticides and partially reduced the cypermethrin content (53%) from aqueous solutions. Unlike the untransformed yeast, P. pastoris HaGST-8 grew efficiently in media supplemented with pesticide mixtures (200 and 400ppm each pesticide) signifying the detoxification ability of HaGST-8. The amino acid sequence of HaGST-8 and the already reported sequence of HaGST-7 had just 2 mismatches. The studies on molecular interaction strengths revealed that HaGST-8 had stronger binding affinities with organophosphate, pyrethroid, organochloride, carbamate and neonicotinoid type of pesticides. The abilities of recombinant HaGST-8 to eliminate pesticides and P. pastoris HaGST-8 to grow profusely in the presence of high level of pesticide content can be applied for removal of such residues from food, water resources and bioremediation.

Mutants of Yarrowia lipolytica NCIM 3589 grown on waste cooking oil as a biofactory for biodiesel production.

BACKGROUND: Oleaginous yeasts are fast emerging as a possible feedstock for biodiesel production. Yarrowia lipolytica, a model oleaginous yeast is known to utilize a variety of hydrophobic substrates for lipid accumulation including waste cooking oil (WCO). Approaches to increase lipid content in this yeast include metabolic engineering which requires manipulation of multiple genes in the lipid biosynthesis pathway. A classical and cost-effective approach, namely, random chemical mutagenesis on the yeast can lead to increased production of biodiesel as is explored here. RESULTS: In this study, chemical mutagenesis using the alkylating agent, N- methyl-N'-nitro-N-nitrosoguanidine (MNNG) as well as an additional treatment with cerulenin, a fatty acid synthase inhibitor generated 800 mutants of Y. lipolytica NCIM 3589 (761 MNNG treated and 39 MNNG + cerulenin treated). A three-stage screening using Sudan Black B plate technique, Nile red fluorimetry and total lipid extraction using solvent was performed, which enabled selection of ten high lipid yielding mutants. Time course studies of all the ten mutants were further undertaken in terms of biomass, lipid yield and lipid content to select three stable mutants (YlB6, YlC7 and YlE1) capable of growing and accumulating lipid on WCO, with lipid contents of 55, 60 and 67% as compared to 45% for the wild type. The mutants demonstrated increased volumetric lipid productivities (0.062, 0.044 and 0.041 g L-1 h-1) as compared to the wild type (0.033 g L-1 h-1). The fatty acid profile of the three mutants consisted of a high content of C16 and C18 saturated and monounsaturated fatty acids and was found to be suitable for biodiesel production. The fuel properties, namely, density, kinematic viscosity, total acid number, iodine value of the three mutants were evaluated and found to lie within the limits specified by internationally accepted standards. Additionally, it was noted that the mutants demonstrated better cetane numbers and higher heating values than the wild type strain. CONCLUSION: The chemical mutagenesis strategy adopted in this study resulted in the successful isolation of three stable high SCO yielding mutants. The mutants, namely, YlB6, YlC7 and YlE1 exhibited a 1.22, 1.33 and 1.49-fold increase in lipid contents when grown on 100 g L-1 waste cooking oil than the parental yeast strain. The fatty acid methyl ester (FAME) profiles of all the three mutants was determined to be suitable for biodiesel suggesting their potential applicability while simultaneously addressing the management of waste cooking oil.

Relationship between salt tolerance and nanoparticle synthesis by Williopsis saturnus NCIM 3298.

This work describes cell associated and extracellular synthesis of nanoparticles by the yeast, Williopsis saturnus. The yeast was able to grow in the absence and presence of sodium chloride (NaCl) and form nanoparticles in a cell associated manner. The content of melanin, a stress-associated pigment was found to be progressively greater in the presence of increasing concentrations of NaCl. With higher quantities of melanin (extracted from yeast cells grown in the presence of 4% of NaCl), smaller sized nanoparticles were obtained. This is the first report on understanding the relationship between halotolerance, production of a stress-related pigment (melanin) and synthesis of nanoparticles with antioxidant properties by using W. saturnus as a model system. The cell free extracts derived from cultures grown in the absence of NaCl were able to mediate extracellular synthesis of gold and silver nanoparticles and the biomolecule mediating nanoparticle synthesis was identified to be a glycolipid. Extracellularly synthesized gold nanoparticles displayed good catalytic activity and rapidly mediated the reduction of 4-nitrophenol to 4-aminophenol.

Biotransformation of hexavalent chromium into extracellular chromium(III) oxide nanoparticles using Schwanniomyces occidentalis.

OBJECTIVES: To demonstrate biotransformation of toxic Cr(VI) ions into Cr2O3 nanoparticles by the yeast Schwanniomyces occidentalis. RESULTS: Reaction mixtures containing S. occidentalis NCIM 3459 and Cr(VI) ions that were initially yellow turned green after 48 h incubation. The coloration was due to the synthesis of chromium (III) oxide nanoparticles (Cr2O3NPs). UV-Visible spectra of the reaction mixtures showed peaks at 445 and 600 nm indicating (4)A2g → (4)T1g and (4)A2g → (4)T2g transitions in Cr2O3, respectively. FTIR profiles suggested the involvement of carboxyl and amide groups in nanoparticle synthesis and stabilization. The Cr2O3NPs ranged between 10 and 60 nm. Their crystalline nature was evident from the selective area electron diffraction and X-ray diffraction patterns. Energy dispersive spectra confirmed the chemical composition of the nanoparticles. These biogenic nanoparticles could find applications in different fields. CONCLUSIONS: S. occidentalis mediated biotransformation of toxic Cr(VI) ions into crystalline extracellular Cr2O3NPs under benign conditions.

Yarrowia lipolytica NCIM 3589, a tropical marine yeast, degrades bromoalkanes by an initial hydrolytic dehalogenation step.

The widespread industrial use of organobromines which are known persistent organic pollutants has led to their accumulation in sediments and water bodies causing harm to animals and humans. While degradation of organochlorines by bacteria is well documented, information regarding degradation pathways of these recalcitrant organobromines is scarce. Hence, their fates and effects on the environment are of concern. The present study shows that a tropical marine yeast, Yarrowia lipolytica NCIM 3589 aerobically degrades bromoalkanes differing in carbon chain length and position of halogen substitution viz., 2-bromopropane (2-BP), 1-bromobutane (1-BB), 1,5 dibromopentane (1,5-DBP) and 1-bromodecane (1-BD) as seen by an increase in cell mass, release of bromide and concomitant decrease in concentration of brominated compound. The amount of bromoalkane degraded was 27.3, 21.9, 18.0 and 38.3 % with degradation rates of 0.076, 0.058, 0.046 and 0.117/day for 2-BP, 1-BB, 1,5-DBP and 1-BD, respectively. The initial product formed respectively were alcohols viz., 2-propanol, 1-butanol, 1-bromo, 5-pentanol and 1-decanol as detected by GC-MS. These were further metabolized to fatty acids viz., 2-propionic, 1-butyric and 1-decanoic acid eventually leading to carbon dioxide formation. Neither higher chain nor brominated fatty acids were detected. An inducible extracellular dehalogenase responsible for removal of bromide was detected with activities of 21.07, 18.82, 18.96 and 26.67 U/ml for 2-BP, 1-BB, 1,5-DBP and 1-BD, respectively. We report here for the first time the proposed aerobic pathway of bromoalkane degradation by an eukaryotic microbe Y. lipolytica 3589, involving an initial hydrolytic dehalogenation step.

Nocardiopsis species as potential sources of diverse and novel extracellular enzymes.

Members of the genus Nocardiopsis are generally encountered in locations that are inherently extreme. They are present in frozen soils, desert sand, compost, saline or hypersaline habitats (marine systems, salterns and soils) and alkaline places (slag dumps, lake soils and sediments). In order to survive under these severe conditions, they produce novel and diverse enzymes that allow them to utilize the available nutrients and to thrive. The members of this genus are multifaceted and release an assortment of extracellular hydrolytic enzymes. They produce enzymes that are cold-adapted (α-amylases), thermotolerant (α-amylases and xylanases), thermoalkalotolerant (cellulases, ß-1,3-glucanases), alkali-tolerant thermostable (inulinases), acid-stable (keratinase) and alkalophilic (serine proteases). Some of the enzymes derived from Nocardiopsis species act on insoluble polymers such as glucans (pachyman and curdlan), keratin (feathers and prion proteins) and polyhydroxyalkanoates. Extreme tolerance exhibited by proteases has been attributed to the presence of some amino acids (Asn and Pro) in loop structures, relocation of multiple salt bridges to outer regions of the protein or the presence of a distinct polyproline II helix. The range of novel enzymes is projected to increase in the forthcoming years, as new isolates are being continually reported, and the development of processes involving such enzymes is envisaged in the future.

Recent advances in production and applications of ectoine, a compatible solute of industrial relevance.

Extremophilic bacteria growing in saline ecosystems are potential producers of biotechnologically important products including compatible solutes. Ectoine/hydroxyectoine are two such solutes that protect cells and associated macromolecules from osmotic, heat, cold and UV stress without interfering with cellular functions. Since ectoine is a high value product, overviewing strategies for improving yields become relevant. Screening of natural isolates, use of inexpensive substrates and response surface methodology approaches have been used to improve bioprocess parameters. In addition, genome mining exercises can aid in identifying hitherto unreported microorganisms with a potential to produce ectoine that can be exploited in the future. Application wise, ectoine has various biotechnological (protein protectant, membrane modulator, DNA protectant, cryoprotective agent, wastewater treatment) and biomedical (dermatoprotectant and in overcoming respiratory and hypersensitivity diseases) uses. The review summarizes current updates on the potential of microorganisms in the production of this industrially relevant metabolite and its varied applications.

3, 4-dihydroxy-L-phenylalanine-derived melanin from Yarrowia lipolytica mediates the synthesis of silver and gold nanostructures.

BACKGROUND: Nanobiotechnology applies the capabilities of biological systems in generating a variety of nano-sized structures. Plants, algae, fungi and bacteria are some systems mediating such reactions. In fungi, the synthesis of melanin is an important strategy for cell-survival under metal-stressed conditions. Yarrowia lipolytica, the biotechnologically significant yeast also produces melanin that sequesters heavy metal ions. The content of this cell-associated melanin is often low and precursors such as L-tyrosine or 3, 4-dihydroxy-L-phenylalanine (L-DOPA) can enhance its production. The induced melanin has not been exploited for the synthesis of nanostructures. In this investigation, we have employed L-DOPA-melanin for the facile synthesis of silver and gold nanostructures. The former have been used for the development of anti-fungal paints. METHODS: Yarrowia lipolytica NCIM 3590 cells were incubated with L-DOPA for 18 h and the resultant dark pigment was subjected to physical and chemical analysis. This biopolymer was used as a reducing and stabilizing agent for the synthesis of silver and gold nanostructures. These nanoparticles were characterized by UV-Visible spectra, X-ray diffraction (XRD) studies, and electron microscopy. Silver nanoparticles were evaluated for anti-fungal activity. RESULTS: The pigment isolated from Y. lipolytica was identified as melanin. The induced pigment reduced silver nitrate and chloroauric acid to silver and gold nanostructures, respectively. The silver nanoparticles were smaller in size (7 nm) and displayed excellent anti-fungal properties towards an Aspergillus sp. isolated from a wall surface. An application of these nanoparticles as effective paint-additives has been demonstrated. CONCLUSION: The yeast mediated enhanced production of the metal-ion-reducing pigment, melanin. A simple and rapid method for the extracellular synthesis of nanoparticles with paint-additive-application was developed.

Bioinspired inimitable cadmium telluride quantum dots for bioimaging purposes.

Synthesis of quantum nanoparticles of specific size, shape and composition are an aspect important in nanotechnology research. Although these nanostructures are routinely synthesized by chemical routes, the use of microorganisms has emerged as a promising option. The synthesis of cadmium telluride (CdTe) quantum dots by two hitherto unreported marine bacteria (Bacillus pumilus and Serratia marcescens) is reported here. Ultraviolet-visible (UV-vis) spectroscopy indicated the synthesis of CdTe nanoparticles and X-ray diffraction (XRD) patterns implicated their crystalline face-centered cubic nature. The size of the synthesized CdTe nanostructures estimated by XRD and dynamic light scattering (DLS) analysis was found to be approximately 10 nm. Photoluminescence (PL) studies were used to confirm the fluorescence properties of these semi-conducting nanoparticles. Scanning electron microscope (SEM) analysis showed the presence of well-defined nanostructures and energy dispersive spectra (EDS) confirmed the microbial synthesis of these nanoparticles. These bio-inspired CdTe nanostructures could be effectively used in imaging of yeast and animal cells. This work thus describes a cost-effective green method for synthesizing highly fluorescent biocompatible CdTe nanoparticles suitable for bio-labeling purposes.

Isolation and characterization of a rare waterborne lytic phage of Salmonella enterica serovar Paratyphi B.

A lytic phage of Salmonella serovar Paratyphi B, named φSPB, was isolated from surface waters of the Pavana River in India. Phage φSPB is a member of the Podoviridae family and is morphologically similar to the 7-11 phages of the C3 morphotype of tailed phages, characterized by a very long, cigar-shaped head. The head measured approximately 153 × 57 nm, and the tail size was 12 × 7 nm. The phage was stable over a wide range of pH (4-9) and temperature (4-40 °C). The adsorption rate constant was 4.7 × 10(-10). Latent and eclipse periods were 10 and 15 min, respectively, and the burst size was 100 plaque-forming units/infected cell after 25 min at 37 °C. The phage DNA was 59 kb in size. Ten major proteins were observed on SDS-PAGE, although some of these proteins could be bacterial contaminants. This is the first report of Salmonella enterica subsp. enterica serovar Paratyphi B phage of C3 morphotype from India that has many unique features, such as high replication potential, short replication time, and stability over a wide range of pH and temperature, making it a promising biocontrol agent against the drug-resistant strains of Salmonella Paratyphi B.