Biomimetic ion substituted and Co-substituted hydroxyapatite nanoparticle synthesis using Serratia Marcescens.

Biomimicry is becoming deep-rooted as part of bioceramics owing to its numerous functional advantages. Naturally occurring hydroxyapatite (HA) apart from primary nano structures are also characterised by various ionic substitutions. The ease of accommodating such key elements into the HA lattice is known to enhance bone healing properties of bioceramics. In this work, hydroxyapatite synthesized via biomimetic approach was substituted with individual as well as multiple cations for potential applications in bone repair. Ion substitutions of Sr, Mg and Zn was carried out on HA for the first time by using Serratia grown in a defined biomineralization medium. The individual ions of varying concentration substituted in Serratia HA (SHA) (Sr SHA, Mg SHA and Zn SHA) were analysed for crystallinity, functional groups, morphology and crystal size. All three showed decreased crystallinity, phase purity, large agglomerated aggregates and needle-shaped morphologies. Fourier transform infrared spectroscopy (FTIR) spectra indicated increased carbonate content of 5.8% resembling that of natural bone. Additionally, the reduced O-H intensities clearly portrayed disruption of HA lattice and subsequent ion-substitution. The novelty of this study lies primarily in investigating the co-substitution of a combination of 1% Sr, Zn and Mg in SHA and establishing the associated change in bone parameters. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images clearly illustrated uniform nano-sized agglomerates of average dimensions of 20-50 nm length and 8-15 nm width for Sr SHA; 10-40 nm length and 8-10 nm width for both Zn SHA and Mg SHA and 40-70 nm length and 4-10 nm width in the case of 1% Sr, Zn, Mg SHA. In both individual as well as co-substitutions, significant peak shifts were not observed possibly due to the lower concentrations. However, cell volumes increased in both cases due to presence of Sr2+ validating its dominant integration into the SHA lattice. Rich trace ion deposition was presented by energy dispersive X-ray spectroscopy (EDS) and quantified using inductively coupled plasma optical emission spectrometer (ICP-OES). In vitro cytotoxicity studies in three cell lines viz. NIH/3T3 fibroblast cells, MG-63 osteosarcoma cells and RAW 264.7 macrophages showed more than 90% cell viability proving the biocompatible nature of 1% Sr, Zn and Mg in SHA. Microbial biomineralization by Serratia produced nanocrystals of HA that mimicked "bone-like apatite" as evidenced by pure phase, carbonated groups, reduced crystallinity, nano agglomerates, variations in cell parameters, rich ion deposition and non-toxic nature. Therefore ion-substituted and co-substituted biomineralized nano SHA appears to be a suitable candidate for applications in biomedicine addressing bone injuries and aiding regeneration as a result of its characteristics close to that of the human bone.

Studies on expression levels of pil Q and fli P genes during bio-electrogenic process in Kluyvera georgiana MCC 3673.

The bacterium Kluyvera georgiana MCC 3673 transfers electrons directly to the electrode for bio-electricity generation in microbial fuel cell (MFC). This could be due to the formation of biofilm on the surface of electrode or with through the extracellular appendages, or both. The role of extracellular appendages pili and flagella in exo-electron transfer mechanism was investigated. The expression level of the genes fli P and pil Q for pili and flagella, respectively, in K. georgiana MCC 3673 was compared in MFC and in shake flask. The transcript analysis was done by qRT-PCR at different times and conditions. The expression level of pil Q transcript in K. georgiana MCC 3673 showed over twofold higher expression during bio-electrogenic process, compared to the one inoculated in shake flask. Similarly, fli P had also showed similar kind of expression in MFC compared to that in shake flask. Higher level of pil Q and fli P transcripts were observed throughout bio-electrogenic process. The level of pil Q was found to be nearly fourfold higher in biofilm-forming cells forming compared to the cells in suspension form. The obtained results suggest that flagella have a role in movement of bacterium towards electrode for donating the electron in absence of oxygen, and pili aiding in adhering on the surface of electrode and forming biofilm. The cumulative effect of fli P and pil Q resulted in exo-electron transfer to the electrode and bio-electricity generation process. The open circuit potential (OCV) of + 0.7 V was produced with the maximum power density of 393 ± 14 mW/m2 in MFC.

Laccase Immobilization Strategies for Application as a Cathode Catalyst in Microbial Fuel Cells for Azo Dye Decolourization.

Enzymatic biocathodes have the potential to replace platinum as an expensive catalyst for the oxygen reduction reaction in microbial fuel cells (MFCs). However, enzymes are fragile and prone to loss of activity with time. This could be circumvented by using suitable immobilization techniques to maintain the activity and increase longevity of the enzyme. In the present study, laccase from Trametes versicolor was immobilized using three different approaches, i.e., crosslinking with electropolymerized polyaniline (PANI), entrapment in copper alginate beads (Cu-Alg), and encapsulation in Nafion micelles (Nafion), in the absence of redox mediators. These laccase systems were employed in cathode chambers of MFCs for decolourization of Acid orange 7 (AO7) dye. The biocatalyst in the anode chamber was Shewanella oneidensis MR-1 in each case. The enzyme in the immobilized states was compared with freely suspended enzyme with respect to dye decolourization at the cathode, enzyme activity retention, power production, and reusability. PANI laccase showed the highest stability and activity, producing a power density of 38 ± 1.7 mW m-2 compared to 25.6 ± 2.1 mW m-2 for Nafion laccase, 14.7 ± 1.04 mW m-2 for Cu-Alg laccase, and 28 ± 0.98 mW m-2 for the freely suspended enzyme. There was 81% enzyme activity retained after 1 cycle (5 days) for PANI laccase compared to 69% for Nafion and 61.5% activity for Cu-alginate laccase and 23.8% activity retention for the freely suspended laccase compared to initial activity. The dye decolourization was highest for freely suspended enzyme with over 85% decolourization whereas for PANI it was 75.6%, Nafion 73%, and 81% Cu-alginate systems, respectively. All the immobilized laccase systems were reusable for two more cycles. The current study explores the potential of laccase immobilized biocathode for dye decolourization in a microbial fuel cell.

Characterization of membrane vesicles secreted by seaweed associated bacterium Alteromonas macleodii KS62.

Recent studies have reported abundant presence of bacterial extracellular membrane vesicles in the marine environment. However, the ecological significance of these bacterial vesicles in the marine environment is only beginning to be explored. In present study, for the first time we report and characterize membrane vesicles secreted by a seaweed associated bacterium, Alteromonas macleodii KS62. Proteomics studies revealed that the vesicle proteome was rich in hydrolytic enzymes (30%) like glycoside hydrolases, proteases, sulphatases, lipases, nucleases and phosphatases. Zymography experiments and enzyme assays established that the vesicles carry active κ-carrageenan degrading enzymes. κ-carrageenan is a major polysaccharide of cell walls of certain red seaweeds like Kappaphycus. Purified membrane vesicles were successfully able to degrade Kappaphycus biomass. Based on these results, we discuss how the hydrolase-rich vesicles may play a role in red seaweed cell wall degradation so that the bacteria can invade and colonise the seaweed biomass establishing a saprophytic lifestyle. We also discuss the role of these vesicles in nutrient acquisition and their ecological significance in the marine environment.

Xerogel based catalyst for improved cathode performance in microbial fuel cells.

In a microbial fuel cell (MFC) the reduction reaction at cathode has been a limiting factor in achieving maximum power density, and numerous strategies have been implemented in an attempt to overcome this. Herein, we demonstrate that carbon xerogel (CX) doped with iron (Fe) and nitrogen (N) followed by modification with graphene oxide (GO) is an efficient catalyst for MFCs. The CXFeNGO catalyst was characterized using a scanning electron microscope, and X-ray diffraction, and the catalytic activity was confirmed using cyclic voltammetry studies. At the anode, colonization of bacterial cells on the electrode surface, forming a biofilm, was observed. When the CXFeNGO-modified electrode was used at the cathode in the MFC, a maximum power density of 176.5 ± 6 mW m-2 was obtained, compared to that of plain graphite electrode, which produced 139.1 ± 4 mW m-2. The power density of the modified electrode is thus 26.8% higher. The power density further increased to 48.6% when the pH of the catholyte was increased to 12, producing a power density of 207 ± 4 mW m-2.

Capillary flow-driven microfluidic device with wettability gradient and sedimentation effects for blood plasma separation.

We report a capillary flow-driven microfluidic device for blood-plasma separation that comprises a cylindrical well between a pair of bottom and top channels. Exposure of the well to oxygen-plasma creates wettability gradient on its inner surface with its ends hydrophilic and middle portion hydrophobic. Due to capillary action, sample blood self-infuses into bottom channel and rises up the well. Separation of plasma occurs at the hydrophobic patch due to formation of a 'self-built-in filter' and sedimentation. Capillary velocity is predicted using a model and validated using experimental data. Sedimentation of RBCs is explained using modified Steinour's model and correlation between settling velocity and liquid concentration is found. Variation of contact angle on inner surface of the well is characterized and effects of well diameter and height and dilution ratio on plasma separation rate are investigated. With a well of 1.0 mm diameter and 4.0 mm height, 2.0 µl of plasma was obtained (from <10 µl whole blood) in 15 min with a purification efficiency of 99.9%. Detection of glucose was demonstrated with the plasma obtained. Wetting property of channels was maintained by storing in DI water under vacuum and performance of the device was found to be unaffected over three weeks.

Decolourisation of Acid orange 7 in a microbial fuel cell with a laccase-based biocathode: Influence of mitigating pH changes in the cathode chamber.

Biocathodes may be a suitable replacement of platinum in microbial fuel cells (MFCs) if the cost of MFCs is to be reduced. However, the use of enzymes as bio-cathodes is fraught with loss of activity as time progresses. A possible cause of this loss in activity might be pH increase in the cathode as pH gradients in MFCs are well known. This pH increase is however, accompanied by simultaneous increase in salinity; therefore salinity may be a confounding variable. This study investigated various ways of mitigating pH changes in the cathode of MFCs and their effect on laccase activity and decolourisation of a model azo dye Acid orange 7 in the anode chamber. Experiments were run with catholyte pH automatically controlled via feedback control or by using acetate buffers (pH 4.5) of various strength (100mM and 200mM), with CMI7000 as the cation exchange membrane. A comparison was also made between use of CMI7000 and Nafion 117 as the transport properties of cations for both membranes (hence their potential effects on pH changes in the cathode) are different. Results show that using Nafion 117 membrane limits salinity and pH changes in the cathode (100mM acetate buffer as catholyte) leading to prolonged laccase activity and faster AO7 decolourisation compared to using CMI7000 as a membrane; similarly automatic pH control in the cathode chamber was found to be better than using 200mM acetate buffer. It is suggested that while pH control in the cathode chamber is important, it does not guarantee sustained laccase activity; as salinity increases affect the activity and it could be mitigated using a cation selective membrane.

Capillary flow of blood in a microchannel with differential wetting for blood plasma separation and on-chip glucose detection.

We report capillary flow of blood in a microchannel with differential wetting for the separation of a plasma from sample blood and subsequent on-chip detection of glucose present in a plasma. A rectangular polydimethylsiloxane microchannel with hydrophilic walls (on three sides) achieved by using oxygen plasma exposure enables capillary flow of blood introduced at the device inlet through the microchannel. A hydrophobic region (on all four sides) in the microchannel impedes the flow of sample blood, and the accumulated blood cells at the region form a filter to facilitate the separation of a plasma. The modified wetting property of the walls and hence the device performance could be retained for a few weeks by covering the channels with deionised water. The effects of the channel cross-section, exposure time, waiting time, and location and length of the hydrophobic region on the volume of the collected plasma are studied. Using a channel cross-section of 1000 × 400 µm, an exposure time of 2 min, a waiting time of 10 min, and a hydrophobic region of width 1.0 cm located at 10 mm from the device inlet, 450 nl of plasma was obtained within 15 min. The performance of the device was found to be unaffected (provides 450 nl of plasma in 15 min) even after 15 days. The purification efficiency and plasma recovery of the device were measured and found to be comparable with that obtained using the conventional centrifugation process. Detection of glucose at different concentrations in whole blood of normal and diabetic patients was performed (using 5 µl of sample blood within 15 min) to demonstrate the compatibility of the device with integrated detection modules.

Development of a microfluidic device for cell concentration and blood cell-plasma separation.

This work presents design, fabrication and test of a microfluidic device which employs Fahraeus-Lindqvist and Zweifach-Fung effects for cell concentration and blood cell-plasma separation. The device design comprises a straight main channel with a series of branched channels placed symmetrically on both sides of the main channel. The design implements constrictions before each junction (branching point) in order to direct cells that would have migrated closer to the wall (naturally or after liquid extraction at a junction) towards the centre of the main channel. Theoretical and numerical analysis are performed for design of the microchannel network to ensure that a minimum flow rate ratio (of 2.5:1, main channel-to-side channels) is maintained at each junction and predict flow rate at the plasma outlet. The dimensions and location of the constrictions were determined using numerical simulations. The effect of presence of constrictions before the junctions was demonstrated by comparing the performances of the device with and without constrictions. To demonstrate the performance of the device, initial experiments were performed with polystyrene microbeads (10 and 15 µm size) and droplets. Finally, the device was used for concentration of HL60 cells and separation of plasma and cells in diluted blood samples. The cell concentration and blood-plasma purification efficiency was quantified using Haemocytometer and Fluorescence-Activated Cell Sorter (FACS). A seven-fold cell concentration was obtained with HL60 cells and a purification efficiency of 70 % and plasma recovery of 80 % was observed for diluted (1:20) blood sample. FACS was used to identify cell lysis and the cell viability was checked using Trypan Blue test which showed that more than 99 % cells are alive indicating the suitability of the device for practical use. The proposed device has potential to be used as a sample preparation module in lab on chip based diagnostic platforms.

Finger millet bran supplementation alleviates obesity-induced oxidative stress, inflammation and gut microbial derangements in high-fat diet-fed mice.

Several epidemiological studies have shown that the consumption of finger millet (FM) alleviates diabetes-related complications. In the present study, the effect of finger millet whole grain (FM-WG) and bran (FM-BR) supplementation was evaluated in high-fat diet-fed LACA mice for 12 weeks. Mice were divided into four groups: control group fed a normal diet (10 % fat as energy); a group fed a high-fat diet; a group fed the same high-fat diet supplemented with FM-BR; a group fed the same high-fat diet supplemented with FM-WG. The inclusion of FM-BR at 10 % (w/w) in a high-fat diet had more beneficial effects than that of FM-WG. FM-BR supplementation prevented body weight gain, improved lipid profile and anti-inflammatory status, alleviated oxidative stress, regulated the expression levels of several obesity-related genes, increased the abundance of beneficial gut bacteria (Lactobacillus, Bifidobacteria and Roseburia) and suppressed the abundance of Enterobacter in caecal contents (P≤ 0·05). In conclusion, FM-BR supplementation could be an effective strategy for preventing high-fat diet-induced changes and developing FM-BR-enriched functional foods.

Oxidative stress protection and glutathione metabolism in response to hydrogen peroxide and menadione in riboflavinogenic fungus Ashbya gossypii.

Ashbya gossypii is a plant pathogen and a natural overproducer of riboflavin and is used for industrial riboflavin production. A few literature reports depict a link between riboflavin overproduction and stress in this fungus. However, the stress protection mechanisms and glutathione metabolism are not much explored in A. gossypii. In the present study, an increase in the activity of catalase and superoxide dismutase was observed in response to hydrogen peroxide and menadione. The lipid peroxide and membrane lipid peroxide levels were increased by H2O2 and menadione, indicating oxidative damage. The glutathione metabolism was altered with a significant increase in oxidized glutathione (GSSG), glutathione peroxidase (GPX), glutathione S transferase (GST), and glutathione reductase (GR) and a decrease in reduced glutathione (GSH) levels in the presence of H2O2 and menadione. Expression of the genes involved in stress mechanism was analyzed in response to the stressors by semiquantitative RT-PCR. The messenger RNA (mRNA) levels of CTT1, SOD1, GSH1, YAP1, and RIB3 were increased by H2O2 and menadione, indicating the effect of stress at the transcriptional level. A preliminary bioinformatics study for the presence of stress response elements (STRE)/Yap response elements (YRE) depicted that the glutathione metabolic genes, stress genes, and the RIB genes hosted either STRE/YRE, which may enable induction of these genes during stress.

Purification and characterization of novel halo-acid-alkali-thermo-stable xylanase from Gracilibacillus sp. TSCPVG.

An aerobic xylanolytic moderately halophilic and alkali-tolerant bacterium, Gracilibacillus sp. TSCPVG, produces multiple xylanases of unusual halo-acid-alkali-thermo-stable nature. The purification of a major xylanase from TSCPVG culture supernatant was achieved by hydrophobic and gel permeation chromatographic methods followed by electroelution from preparatory PAGE. The molecular mass of the purified xylanase was 42 kDa, as analyzed by SDS-PAGE, with a pI value of 6.1. It exhibited maximal activity in 3.5 % NaCl and retained over 75 % of its activity across the broad salinity range of 0-30 % NaCl, indicating a high halo-tolerance. It showed maximal activity at pH 7.5 and had retained 63 % of its activity at pH 5.0 and 73 % at pH 10.5, signifying the tolerance to broad acid to alkaline conditions. With birchwood xylan as a substrate, K m and specific activity values were 21 mg/ml and 1,667 U/mg, respectively. It is an endoxylanase that degrades xylan to xylose and xylobiose and had no activity on p-nitrophenyl-ß-D-xylopyranoside, p-nitrophenyl-ß-D-glucopyranoside, p-nitrophenyl acetate, carboxymethylcellulose, and filter paper. Since it showed remarkable stability over different salinities, broad pH, and temperature ranges, it is promising for application in many industries.

An assessment of temporal variations in physicochemical and microbiological properties of barmouths and lagoons in Chennai (Southeast coast of India).

Two estuary and two coastal lagoon stations along Chennai, Southeast coast of India were monitored for 1year to study both physicochemical and microbiological properties of the water. Influence of the marine environment over the systems was evident by elevated salinity levels. Considerable concentrations of total heterotrophic bacterial count and fecal bacteria such as total coliforms, fecal coliforms and fecal streptococci were observed throughout the study period which evinced a pattern of anthropogenic activities. Principle component analysis was employed for assessing the overall pattern of variation within the data sets. Climatic variation was highly correlated with changes in water quality, i.e. the Northeast monsoon and Summer had influenced considerably the microbial occurrence as well as the physicochemical parameters such as total suspended solids, chloride, sulphate and salinity. However, the effect of the Southwest monsoon was less prominent than the Northeast monsoon with its heavy rains. As both estuaries revealed elevated concentrations of polluted water, these stations can be used as indicators or alerts for the water quality along the coastal zone of Chennai.

Development of fluorescent reporter tagged RIB gene cassettes for replicative transformation, early expression, and enhanced riboflavin production in Eremothecium ashbyi.

Eremothecium ashbyi is a riboflavin overproducing filamentous fungus in which the metabolic pathways have not been genetically characterized. Two genes of the riboflavin biosynthetic (RIB) pathway, RIB1 and RIB3, which encode GTP-cyclohydrolase II (GCH II) and 3,4-dihydroxy-2-butanone 4-phosphate (DHBP) synthase respectively, were selected for the present study. The two RIB genes under their native promoters were obtained from Ashbya gossypii genomic library. Yeast enhanced green fluorescent protein (yEGFP) and mCherry genes were tagged to the C-terminal ends of RIB1 and RIB3 genes to analyse the functionality of the RIB transgenes in E. ashbyi. Shuttle vectors with the reporter tagged RIB genes contained the Escherichia coli kan(R) gene and Saccharomyces cerevisiae ARS element. On transformation with these plasmids, the ARS element was found to be functional in E. ashbyi. The E. ashbyi transcription factors could recognize the Ashbya RIB gene promoters and express the reporter tagged RIB genes as cytoplasmic proteins, in early cell development. Replicative transformants carrying RIB1-mCherry plasmids showed 2.95 times more GCH II activity and 2.44 times more riboflavin production when compared to untransformed. This is the first report of genetic transformation of E. ashbyi and is of significance as the first step towards genetic engineering of this genus.

Sequence analysis and structural characterization of a glyceraldehyde-3-phosphate dehydrogenase gene from the phytopathogenic fungus Eremothecium ashbyi.

Eremothecium ashbyi is a phytopathogenic fungus infesting cotton, soybeans and several other plants. This highly flavinogenic fungus has been phylogenetically characterized, but the genetic aspects of its central metabolic and riboflavin biosynthetic pathways are unknown. An ORF of 996 bp was obtained from E. ashbyi by using degenerate primers for glyceraldehyde-3-phosphate dehydrogenase (GPD) through reverse transcriptase polymerase chain reaction (RT-PCR) and 5'-3' rapid amplification of cDNA ends (RACE-PCR). This nucleotide sequence had a high similarity of 88% with GPD sequence of Ashbya gossypii. The putative GPD peptide of 331-aa had a high similarity of 85% with the GPD sequence from other ascomycetes. The ORF had an unusually strong codon bias with 5 amino acids showing strict preference of a single codon. The theoretical molecular weight for the putative peptide was 35.58 kDa with an estimated pI of 5.7. A neighbor-joining tree showed that the putative peptide from E. ashbyi displayed the highest similarity to GPD of A. gossypii. The gene sequence is available at the GenBank, accession number EU717696. Homology modeling done with Kluyveromyces marxianus GPD (PDB: 2I5P) as template indicated high structural similarity.

Molecular and structural characterization of GTP-cyclohydrolase II in Eremothecium ashbyi NRRL Y-1363: cDNA cloning, comparative sequence analysis and molecular modeling.

GTP-cyclohydrolase II (GCH II) encoded by RIB1 gene catalyzes the first committed step in the riboflavin biosynthetic pathway. We report here the cloning and characterization of the entire RIB1 ORF (EaRIB1) of 942bp by reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE-PCR) in Eremothecium ashbyi where it was found to be present as a single-copy gene. EaRIB1 sequence is available at the GenBank Accession Number EF565374. The putative peptide of 313-aa has a high similarity of 60-70% with GCH II sequences from other ascomycete fungi. Gene expression and alignment studies confirmed the functional annotation of this gene. Homology model was developed with Escherichia coli (PDB 2BZ1) as template to identify the catalytic domains and to explore its functional architecture. We report here the first three-dimensional model of any fungal GCH II which due to its absence in humans assumes significance for anti-fungal drug targeting.

Stimulation of biomethanation by Clostridium sp. PXYL1 in coculture with a Methanosarcina strain PMET1 at psychrophilic temperatures.

AIM: Bioaugumentation of low temperature biogas production was attempted by addition of cold-adapted Clostridium and a methanogen. METHODS AND RESULTS: A psychrotrophic xylanolytic acetogenic strain Clostridium sp. PXYL1 growing optimally at 20 degrees C and pH 5.3 and a Methanosarcina strain, PMET1, growing optimally on acetate and producing methane at 15 degrees C were isolated from a cattle manure digester. Anaerobic conversion of xylose at 15 degrees C with the coculture of the two strains was performed, and batch culture methane production characteristics indicated that methanogenesis occurred via acetate through 'acetoclastic' pathway. Stimulation studies were also undertaken to evaluate the effect of exogenous addition of the coculture on biogas yields at 15 degrees C. Addition of 3 ml of PXYL1 at the rate of 12 x 10(2) CFU ml(-1) increased the biogas 1.7-fold (33 l per kg cowdung) when compared to control (19.3 l per kg cowdung) as well as increased the volatile fatty acid (VFA) levels to 3210 mg l(-1) when compared to 1140 mg l(-1) in controls. Exogenous of addition of 10 ml PMET1 inoculum at the rate of 6.8 + or - 10(2) CFU ml(-1) in addition to PXYL1 served to further improve the biogas yields to 46 l kg(-1) as well as significantly brought down the VFA levels to 1350 mg l(-1). CONCLUSIONS: Our results suggest that the rate-limiting methanogenic step at low temperatures could be overcome and that biogas yields improved by manipulating the population of the acetoclastic methanogens. SIGNIFICANCE AND IMPACT OF THE STUDY: Stimulation of biomethanation at low temperature by coculture.

Do earthworms affect dynamics of functional response and genetic structure of microbial community in a lab-scale composting system?

Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH(4)(+)-N and ash content) showed similar evolution in both systems except a higher NH(4)(+)-N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.

High power density from Pt thin film electrodes based microbial fuel cell.

Microbial Fuel Cells (MFC) are robust devices capable of taping biological energy, converting sugars into potential sources of energy. Persistent efforts are directed towards increasing power output. However, they have not been researched to the extent of making them competitive with chemical fuel cells. The power generated in a dual-chamber MFC using neutral red (NR) as the electron mediator has been previously shown to be 152.4 mW/m2 at 412.5 mA/m2 of current density. In the present work we show that Pt thin film coated carbon paper as electrodes increase the performance of a microbial fuel cell compared to conventionally employed electrodes. The results obtained using E. coli based microbial fuel cell with methylene blue and neutral red as the electron mediator, potassium ferricyanide in the cathode compartment were systematically studied and the results obtained with Pt thin film coated over carbon paper as electrodes were compared with that of graphite electrodes. Platinum coated carbon electrodes were found to be better over the previously used for microbial fuel cells and at the same time are cheaper than the preferred pure platinum electrodes.

Structural divergence of bacterial communities from functionally similar laboratory-scale vermicomposts assessed by PCR-CE-SSCP.

AIMS: To evaluate bacterial community structure and dynamics in triplicate vermicomposts made from the same start-up material, along with certain physico-chemical changes. METHODS AND RESULTS: The physico-chemical parameters (pH, temperature, carbon, nitrogen, soluble substances and cellulose) evolved similarly in the triplicate vermicomposts, indicating a steady function. The 16S bacterial gene abundance remained constant over time. To monitor changes in the bacterial community structure, fingerprinting based on capillary electrophoresis single-strand conformation polymorphism was employed. A rise in bacterial diversity occurred after precomposting and it remained stable during the maturation phase. However, a rapid shift in the structure of the bacterial community in the vermicompost replicates was noted at the beginning that stabilized with the process maturation. Multivariate analyses showed different patterns of bacterial community evolution in each vermicompost that did not correlate with the physico-chemical changes. CONCLUSIONS: The broad-scale functions remained similar in the triplicates, with stable bacterial abundance and diversity despite fluctuation in the community structure. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has demonstrated that microbial fingerprinting with multivariate analysis can provide significant understanding of community structure and also clearly suggests that an ecosystem's efficacy could be the outcome of functional redundancy whereby a number of species carry out the same function.