Kapil Deo Pandey

Hydrogen production by Rhodopseudomonas at the expense of vegetable starch, sugarcane juice and whey

Four local strains of Rhodopseudomonas sp. (BHU strains 1–4) evolved hydrogen at the expense of potato starch, sugarcane juice and whey (1% in each case) in the presence of light (2 klux), under anaerobic conditions (argon/CO2, 95/5, v/v). Among the three substrates, sugarcane juice supported the maximum level of H2 production, followed by potato starch and whey at the rates of 45, 30 and 25 μl H2 h−1 mg−1 bacterial cell dry weight, respectively. Although elevated temperature (45°C) suppressed H2 evolution by strains 1, 2 and 3, the thermotolerant strain (BHU strain 4) has shown encouraging results. Alginate-immobilized cells under an identical experimental regime, exhibited an almost one-and-a-half times improvement in H2 production in the cases of all the above substrates over their free cell counterpart. Preliminary experiments have shown the presence of amylase in all the bacterial strains and work is in progress to characterize this enzyme so that the system could be used for efficient consumption of starch-based agro- products.

Enhanced hydrogen production by coupled system of Halobacterium halobium and chloroplast after entrapment within reverse micelles

Reverse micelles were used for the enhanced rate of photoproduction of hydrogen using the coupled system of Halobacterium halobium and chloroplasts organelles. Different combinations of organic solvents and surfactants were used for generating reverse micelles. A several fold enhancement in the rate of H2 production was observed when the coupled system was entrapped within reverse micelles as compared to the aqueous suspension where no detectable H2 was produced. The coupled system immobilized in reverse micelles formed by sodium lauryl sulfate and carbontetrachloride yielded maximum rate of H2 evolution. The optimum temperature for such hydrogen production was 40°C using light of 520–570 nm wavelength and 100 lux intensity.

Cyanobacteria in alkaline soil and the effect of cyanobacteria inoculation with pyrite amendments on their reclamation

The succession of cyanobacteria was studied in a usar (alfisol, solonetz, alkaline) soil, located in a tropical region of upper Gangetic plain, following the first rainfall for a period of 10 months (i.e., July–April). A dozen cyanobacteria were identified to grow on the soil surface and their appearance was in the following order: Microcoleus sp., Calothrix brevissima, Scytonema sp., Cylindrosprmum licheniformae, Cylindrosprmum fertilissima, Nostoc calcicola, Nostoc punctiformae, Aphanothece parietina, Nostoc commune, Aulosira fertilissima, Phormidium sp., and Oscillatoria sp. Among these cyanobacteria, N. calcicola was the dominant species. N. calcicola was inoculated on the alkaline soil and incubated under ambient conditions in the light for 2 years in the laboratory. Changes in soil properties were more rapid after the incorporation of pyrite (FeS2). Recovery was monitored by using a filamentous heterocystous cyanobacterium N. calcicola and its bicarbonate-resistant (HCO3−R) mutant. The mutant strain showed better response to modification of soil pH following growth in soil.

Environmental Determinants of Soil Methane Oxidation and Methanotrophs

Methane (CH4) is one of the strongest greenhouse gases. Sources of CH4 are anthropogenic and natural, former playing ∼60% role. Major sink for CH4 are the atmospheric OH and Cl radicals (originating from CFCs), and biological system. Biological CH4 sink is mediated through the CH4 oxidation by the specialized group of bacteria called methanotrophs (MB). Methanotrophs have been reported from almost all the soil systems such as sediments, oceans, extremes of pH, salinity, and temperature. They oxidize methane aerobically in the presence of the enzyme methane monooxygenase (MMO). Anaerobic methane oxidation (AOM) also occurs in marine ecosystem where sulfate is final electron acceptor. Methanotrophs are of two types, first is cultured and low affinity group while the second is uncultured and high affinity group. Most of them can be grouped as Type I and Type II belonging to γ- and α-Proteobacteria, respectively. They may constitute up to 2% of total bacterial population in soil depending on physical factors such as water, temperature, soil depth, pH, texture, gaseous atmosphere (methane, oxygen, and CO2), soil organic content, and biological factors such as vegetation and microbial consortia. Besides, anthropogenic factors such as fertilizers, agro- and organochemicals, and land use pattern have strong influence over them. Global climate change including acid rain, high temperature, increasing rainfall, and drought have potential to affect the global methane sink activity. The authors attempt to review the recent advances made regarding CH4 oxidation and methanotrophic population size as well as community structure as affected by the various natural and anthropogenic factors.

Nitrogenase activity of the antarctic cyanobacteriumNostoc commune: Influence of temperature

Nitrogenase activity (C2H2 reduction) ofNostoc commune isolated from Schirmacher Oasis (Antarctica) was compared withNostoc muscorum, N. calcicola, Anabaena doliolum andGloeocapsa sp. The temperature profile of acetylene reduction (5–30 °C) forN. commune revealed (a) that the highest rate of nitrogenase activity was at 25±1 °C, (b) that it was low (69 %) in comparison withN. muscorum, and (c) that nitrogenase activity continued at lower temperatures, which was not evident for other cyanobacteria. The results suggest thatN. commune is adapted to lower temperatures in terms of nitrogen fixation.

Nutrient status, algal and cyanobacterial flora of six fresh water streams of Schirmacher Oasis, Antarctica

The algal and cyanobacterial flora and the chemical environment of six freshwater streams of Schirmacher Oasis, Antarctica were investigated. Over 30 species of algae, predominantly cyanobacteria (Cyanophyceae), were recorded. N2-fixing species, both heterocystous and unicellular diazotrophs, contributed more than 50% to the counts and their dominance was greatest in the middle of the stream where nitrogen and other nutrients were low. Green algae and diatoms also contributed to the flora. The species composition varied between streams. Glacial and snow drift meltwater streams contained a distinctive community. Based on diversity indices, these streams could be classified into two clusters.

Hydrogen photoproduction by filamentous non-heterocystous cyanobacterium Plectonema boryanum and simultaneous release of ammonia

Abstract Plectonema boryanum (filamentous, non-heterocystous cyanobacterium) photoproduced H 2 when cells grown aerobically in nitrate were transferred to microaerobic or anaerobic conditions without nitrate. It was observed that H 2 photoproducing cells simultaneously excreted ammonium in the medium, which was possibly due to phycocyanin degradation [decrease in chlorophyll a (Chl a ):phycocyanin ratio in comparison to aerobic nitrate-grown cells]. Although nitrogenase (measured as H 2 evolution) was induced in Ar:CO 2 (96:4 v/v), inclusion of N 2 in the gas phase (Ar:CO 2 :N 2 , 72:4:24 v/v) resulted in a 2-fold increase in H 2 evolution. Addition of l -methionine DL-sulphoximine (MSX, glutamine-synthetase inhibitor), besides stimulating ammonium excretion in the medium, resulted in a 4.5-fold increment of H 2 photoproduction (1.43 μmol H 2 mg −1 dry wt h −1 ) in comparison to cells in Ar:CO 2 gas phase (0.31 μmol H 2 mg −1 dry wt h −1 ). Inhibition of photosystem II by 3(3,4-dichlorophenyl)1,1-dimethyl urea (DCMU) caused an increment of 1.6 and 3.2-fold in Ar:CO 2 and Ar:CO 2 :N 2 , respectively, in comparison to cells incubated in Ar:CO 2 gas phase alone. Simultaneous production of H 2 and NH 4 + was at a maximum when MSX and DCMU were added together in suboptical concentrations. Immobilization of cells in calcium alginate prolonged the duration (12 days) of H 2 evolution and NH 4 − excretion.

Enhanced hydrogen photoproduction by non-heterocystous cyanobacterium Plectonema boryanum

Abstract Nitrogenase activity was derepressed in Plectonema boryanum following 18–24 h of microaerobic incubation. The cyanobacterium evolved hydrogen at a slow rate. Addition of reducing substances (sulfide, sulfite or dithionite) to the diazotrophic cultures resulted in an increase in nitrogenase activity or photoproduction of hydrogen. The reducing substances also restored phycocyanin degradation.

Endophytic bacteria: a new source of bioactive compounds

In recent years, bioactive compounds are in high demand in the pharmaceuticals and naturopathy, due to their health benefits to human and plants. Microorganisms synthesize these compounds and some enzymes either alone or in association with plants. Microbes residing inside the plant tissues, known as endophytes, also produce an array of these compounds. Endophytic actinomycetes act as a promising resource of biotechnologically valuable bioactive compounds and secondary metabolites. Endophytic Streptomyces sp. produced some novel antibiotics which are effective against multi-drug-resistant bacteria Antimicrobial agents produced by endophytes are eco-friendly, toxic to pathogens and do not harm the human. Endophytic inoculation of the plants modulates the synthesis of bioactive compounds with high pharmaceutical properties besides promoting growth of the plants. Hydrolases, the extracellular enzymes, produced by endophytic bacteria, help the plants to establish systemic resistance against pathogens invasion. Phytohormones produced by endophytes play an essential role in plant development and drought resistance management. The high diversity of endophytes and their adaptation to various environmental stresses seem to be an untapped source of new secondary metabolites. The present review summarizes the role of endophytic bacteria in synthesis and modulation of bioactive compounds.

NITROGEN-FIXATION BY NON-HETEROCYSTOUS CYANOBACTERIAIN AN ANTARCTIC ECOSYSTEM

Unicellular, non-heterocystous, diazotrophic cyanobacteria Gloeocapsa sp. isolatedfrom Schirmacher Oasis, Antarctica, showed N2-fixation (C2H2-reduction) whichwas comparable to that of Gloeocapsa sp. isolated from a tropical rice field. The optimum temperature of the Antarctic isolate for nitrogenase activity was 20whereas the tropical isolate expressed its maximum activity at 30supported the nitrogenase activity of both the isolates in darkness. The results indicated that the Antarctic isolate behaved differently with respect to temperature compared to the tropical isolate.