Identification of Quorum Quenching N-Acyl Homoserine Lactonases from Priestia aryabhattai J1D and Bacillus cereus G Isolated from the Rhizosphere.

Several pathogenic bacteria communicate using N-acyl homoserine lactone (AHL) as a quorum sensing (QS) molecule. The process of interfering with the QS system is known as quorum quenching (QQ), it is an effective tool to control QS-dependent virulence in pathogens. In the present study, rhizosphere bacterial isolates were screened for their ability to produce AHL lactonase enzyme as QQ molecules, which hydrolyses AHL signalling molecules and consequently blocks the QS system. Potent N-hexanoyl-l-homoserine lactone (C6HSL) hydrolytic QQ activity was detected in rhizosphere isolates namely Bacillus cereus G and Priestia aryabhattai J1D. The cell-free supernatant of the bacterial isolates indicated a reduction in biofilm formation in the human pathogens Vibrio cholerae, Pseudomonas aeruginosa, and Staphylococcus aureus without inhibiting cells, signifying their biocontrol property. Furthermore, liquid chromatography high resolution mass spectrometry analysis confirmed C6HSL hydrolytic activity by AHL lactonase produced by these rhizosphere isolates. Also, the aiiA homologous gene from the bacterial isolates showed similarity with the aiiA lactonase gene from Bacillus species, which was further confirmed by homology modelling. In silico structure analysis by comparing with the structure of Bacillus revealed the similarity in the active site, indicating the same degradation pattern. Based on available reported data, the present study indicates the first report of the presence of the aiiA lactonase gene in P. aryabhattai.

Lactic Acid Bacteria in the Management of Oily Spot Disease of Pomegranate.

The bacterial pathogen of oily spot disease, a major threat to pomegranate growers, was isolated from infected plant parts of pomegranate collected from orchards in Maharashtra, India. The pathogen was identified as Xanthomonas axonopodis pv. punicae (Xap) following phenotypic and molecular characterization by 16S rRNA gene sequencing. It produced pectinase, cellulase, xylanase in medium and in experimentally inoculated tissues with pathogen where pectinase activity was maximum (32.2 U/g). Pearson correlation analysis showed a perfect positive correlation (P < 0.05) between enzyme activity and disease rating scale. This indicates the co-synthesis of hydrolytic enzymes that aid in tissue degradation and suggests their role as virulence factors. Out of 150 indigenously isolated lactic acid bacteria (LAB), Lactococcus lactis subsp. cremoris PB6, Lactobacillus brevis PFR77 and L. lactis subsp. cremoris PFL9, the potent antagonists of Xap, were used in the management of bacterial blight. Under laboratory conditions, cell formulation of PB6, PFR77 and PFL9 were equally effective (P > 0.05) and significantly (P < 0.05) reduced the infection in fruits. Under field conditions, the disease severity index for the treatments where plants received a spray of PB6 with streptocycline, was lowest (4.61%) as compared to cells (15.74%), culture supernatant (20.66%) and their integrated treatments (21.38%), and streptocycline (15.37%) treatments. However, no significant difference (P > 0.05) was noticed between cells and streptocycline treatments, thus, indicating the effectiveness of LAB in treating bacterial blight. This is the first report on the use of antagonistic LAB for the control of oily spot disease of pomegranate.

Synthesis, Characterization and Anti-Biofilm Efficacy of Polypyrrole-Zinc Oxide Composites.

A nanocomposite of Polypyrrole (PPy) and zinc oxide (ZnO), termed as PPy-ZnO, was synthesized by two step route. In the first step, synthesis of PPy was carried out by chemical oxidative route. In the second step, the PPy-ZnO nanocomposite was synthesized under hydrothermal conditions. The as-synthesized PPy-ZnO nanocomposites were characterized using X-ray Diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infra-red (FTIR) and Ultra violetvisible (UV-vis) spectroscopy to reveal the phase, morphology, chemical and optical properties. The physical and chemical characterizations confirmed presence of both PPy and ZnO phases in the nanocomposite. In the present work, antimicrobial activity of the PPy-ZnO nanocomposite against human pathogen Y. lipolytica has been investigated. Attempts have been made to reveal the influence of PPy percentage on the antimicrobial activity. Interestingly, all PPy-ZnO nanocomposites, irrespective of PPy percentage, showed 90 to 95% inhibited growth of Yarrowia lipolytica. The results obtained herein imply the potential of PPy-ZnO biofilm in inhibiting the growth of Y. lipolytica and thus preventing infections caused due to Y. lipolytica in humans.

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.

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.

Psychrotrophic yeast Yarrowia lipolytica NCYC 789 mediates the synthesis of antimicrobial silver nanoparticles via cell-associated melanin.

A psychrotrophic marine strain of the ascomycetous yeast Yarrowia lipolytica (NCYC 789) synthesized silver nanoparticles (AgNPs) in a cell-associated manner. These nanostructures were characterized by UV-Visible spectroscopy and scanning electron microscope-energy dispersive spectrometer (SEM-EDS) analysis. The brown pigment (melanin) involved in metal-interactions was obtained from the cells. This extracted pigment also mediated the synthesis of silver nanoparticles that were characterized by a variety of analytical techniques. The melanin-derived nanoparticles displayed antibiofilm activity. This paper thus reports the synthesis of AgNPs by the biotechnologically important yeast Y. lipolytica; proposes a possible mechanism involved in the synthetic process and describes the use of the bio-inspired nanoparticles as antibiofilm agents.

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.

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.

Removal of hexavalent chromium ions by Yarrowia lipolytica cells modified with phyto-inspired Fe0/Fe3O4 nanoparticles.

The removal of hexavalent chromium [Cr (VI)], an important ground water pollutant by phyto-inspired Fe(0)/Fe(3)O(4) nanocomposite-modified cells of Yarrowia lipolytica (NCIM 3589 and NCIM 3590), was investigated. Electron microscopy and magnetometer studies indicated an effective modification of yeast cell surfaces by the nanocomposites. The effect of pH, temperature, agitation speed, contact time and initial metal ion concentration on the removal of Cr (VI) was determined. The specific uptake values at pH 2.0 were 186.32±3.17 and 137.31±4.53 mg g(-1) for NCIM 3589 and NCIM 3590, respectively, when 1000 mg L(-1) of metal ion concentrations were used. The equilibrium data fitted to Scatchard, Langmuir and linearized Freundlich models suggesting that adsorption played a role in the removal of Cr (VI) ions. The surface modified yeast cells displayed higher values of Langmuir and Scatchard coefficients than the unmodified cells indicating that the former were more efficient in Cr (VI) removal. The enhanced detoxification of Cr (VI) ions by this composite material could be attributed to the reductive power of the Fe(0)/Fe(3)O(4) nanocomposites as well the yeast cell surface functional groups.

Biosynthesis of colloidal gold nanoparticles by Streptomyces sp. NK52 and its anti-lipid peroxidation activity.

Gold nanoparticles (Au-NPs) were synthesized from chloroauric acid using cell free supernatant of Streptomyces sp. NK52 grown in nutrient broth. These nanoparticles were synthesized by varying pH and temperature of the reaction mixture and chloroauric acid concentration. The nanoparticles were characterized by spectrometry, X-ray diffraction, Scanning electron microscopy and energy dispersive spectrometry. Au-NP ranged from 10-100 nm in size and exhibited a polydispersive nature with various shapes like rods, hexagons, triangles, spheres. The diffraction peaks at 2theta = 38.1 degrees and 44.5 degrees could be assigned to the (1 1 1) and (2 0 0) planes of a faced centre cubic (fcc) lattice of gold. Au-NP showed 47% inhibition of lipid peroxidation in vitro. To the best of our knowledge, this is the first report on the rapid biosynthesis of Au-NP using cell free supernatant of Streptomyces sp. and its evaluation for anti-lipid peroxidation.

Bioleaching of fly ash by the tropical marine yeast, Yarrowia lipolytica NCIM 3589.

Fly ash collected from an Indian thermal power plant was characterised by scanning electron microscope (SEM)-energy dispersive spectrometer, X-ray diffraction and energy dispersive X-ray fluorescence analysis. The effect of fly ash on the growth and morphology of a metal-tolerant tropical marine yeast, Yarrowia lipolytica NCIM 3589, was studied. The growth of the yeast was unaffected by the presence 0.1, 0.2 or 0.3 % fly ash although the surface-to-volume ratio decreased. The yeast formed biofilms on immobilized fly ash as evidenced by SEM observations. The organism produced citric acid and additional extracellular proteins in the presence of fly ash. Leaching of metals from fly ash by Y. lipolytica was compared with chemical leaching by citric acid. Yeast cells were most effective in leaching Cu (59.41 %) although other metals (Zn, Ni, Cu and Cr) were also extracted. Transmission electron microscope images showed the deposition of metals at the cell wall, cell membrane and in the cytoplasm. This paper thus reports a potential application of Y. lipolytica for removal of different metals from solid waste material (fly ash).

Removal of Ni (II) ions from aqueous solutions by biosorption onto two strains of Yarrowia lipolytica.

The removal of Ni (II) ions from aqueous solutions by two strains of Yarrowia lipolytica (NCIM 3589 and NCIM 3590) under different environmental conditions was studied. Biosorption of Ni (II) was enhanced with an increase in pH, temperature, agitation, contact time and initial concentration of the metal ion. NCIM 3589 and NCIM 3590 at pH 7.5 in the presence of 1000 mg L(-1) Ni (II) at 35 °C exhibited a maximum uptake of 95.33 mg g(-1) and 85.44 mg g(-1), respectively. The experimental data fitted well to the Langmuir as well as the Freundlich isotherms. Dubinin-Radushkevich (D-R) isotherms suggested that a chemical ion-exchange mechanism was involved in the biosorption process. The biosorption process followed the pseudo-second-order kinetic mechanism with liquid film diffusion being the rate limiting step. Fourier transform infra red (FTIR) spectroscopic studies suggested the possible involvement of hydroxyl, caboxyl, carbonyl and amino groups in process of biosorption. Scanning electron microscopy and energy dispersive spectra (SEM-EDS) confirmed biosorption of Ni (II).

Phyto-inspired silica nanowires: characterization and application in lipase immobilization.

Silica nanostructures were phyto-fabricated on different surfaces by using pomegranate (Punica granatum) leaf extracts. On zinc films, nanowires were obtained. On other surfaces such as silica, alumina, zinc oxide, and glass, spherical aggregates, cubic assemblies, microflakes, and acicular structures, respectively, were observed. The nanowires developed on Zn surfaces were characterized by scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), photoluminescence, and Fourier transform infrared (FTIR) spectroscopic analysis. XRD profiles displayed peaks at 2.4, 4.9, and 12.1° indicating the presence of silica nanostructures. When excited at 340 nm, the reaction mixtures displayed a characteristic blue luminescence at 404 nm. FTIR spectra showed the existence of Si-OH and Si-O-Si bonds. The nanowires were functionalized with amine groups and used for the covalent immobilization of Candida rugosa lipase. The immobilized enzyme displayed better pH and temperature stability and retained 80% activity after 20 cycles. This paper highlights a novel route for the phyto-mediated growth of silica nanowires on Zn surfaces, their characterization and effective use as a matrix for enzyme immobilization.

Banana peel extract mediated synthesis of gold nanoparticles.

Gold nanoparticles were synthesized by using banana peel extract (BPE) as a simple, non-toxic, eco-friendly 'green material'. The boiled, crushed, acetone precipitated, air-dried peel powder was used to reduce chloroauric acid. A variety of nanoparticles were formed when the reaction conditions were altered with respect to pH, BPE content, chloroauric acid concentration and temperature of incubation. The reaction mixtures displayed vivid colors and UV-vis spectra characteristic of gold nanoparticles. Dynamic light scattering (DLS) studies revealed that the average size of the nanoparticles under standard synthetic conditions was around 300nm. Scanning electron microscopy and energy dispersive spectrometry (EDS) confirmed these results. A coffee ring phenomenon, led to the aggregation of the nanoparticles into microcubes and microwire networks towards the periphery of the air-dried samples. X-ray diffraction studies of the samples revealed spectra that were characteristic for gold. Fourier transform infra red (FTIR) spectroscopy indicated the involvement of carboxyl, amine and hydroxyl groups in the synthetic process. The BPE mediated nanoparticles displayed efficient antimicrobial activity towards most of the tested fungal and bacterial cultures.

Environmental and industrial applications of Yarrowia lipolytica.

Yarrowia lipolytica is a fungus that degrades hydrophobic substrates very efficiently. The fungus displays several important characteristics that have encouraged researchers to study various basic biological and biotechnological applications in detail. Although the organism has been used as model system for studying dimorphism, salt tolerance, heterologous protein expression, and lipid accumulation, there are no recent reviews on the environmental and industrial applications of this organism. Included here are applications in bioremediation of environments contaminated with aliphatic and aromatic compounds, organic pollutants, 2,4,6-trinitrotoluene, and metals. A variety of industrially important recent processes for the synthesis of beta-hydroxy butyrate, L-dopa, and emulsifiers have also been reviewed. Production of unique inherent enzymes (inulinases, alpha-mannosidases), novel applications of esterases and lipases, and the use of the fungus for heterologous expression of biotechnologically relevant products have also been highlighted. The review while entailing a general overview focuses critically on some of the recent advances on the applications of this yeast. The examples cited here demonstrate the use of wild-type, mutant as well as genetically manipulated strains of Y. lipolytica for the development of different products, processes, and technologies. This also throws light on how a single organism can be versatile with respect to its metabolic abilities and how it can be exploited for a variety of purposes. This review will thus form a base for future developments in this field.

Removal of chromium (VI) ions from aqueous solution by adsorption onto two marine isolates of Yarrowia lipolytica.

The removal of chromium (VI) ions from aqueous solutions by the biomass of two marine strains of Yarrowia lipolytica (NCIM 3589 and 3590) was studied with respect to pH, temperature, biomass, sea salt concentration, agitation speed, contact time and initial concentration of chromium (VI) ions. Maximum biosorption was observed at pH 1.0 and at a temperature of 35 degrees C. Increase in biomass and sea salts resulted in a decreased metal uptake. With an agitation speed of 130 rpm, equilibrium was attained within 2h. Under optimum conditions, biosorption was enhanced with increasing concentrations of Cr (VI) ions. NCIM 3589 and 3590 displayed a specific uptake of Cr (VI) ions of 63.73+/-1.3 mg g(-1) at a concentration of 950 ppm and 46.09+/-0.23 mg g(-1) at 955 ppm, respectively. Scatchard plot analysis revealed a straight line allowing the data to be fitted in the Langmuir model. The adsorption data obtained also fitted well to the Freundlich isotherm. The surface sequestration of Cr (VI) by Y. lipolytica was investigated with a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS) as well as with ED-X-ray fluorescence (ED-XRF). Fourier transform infrared (FTIR) spectroscopy revealed the involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in chromium binding.