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ABSTRACT: Mangroves form an important ecosystem of Great Nicobar, a continental island in the Bay of Bengal with luxuriant tropical
rainforests. The rhizosphere of the mangrove plants of Great Nicobar was investigated for the presence of arbuscular mycorrhizal
fungus (AMF) and phosphate solubilising bacteria (PSB). The soils of the Great Nicobar mangroves were silt–clays and were
poor in phosphate content. Five species of AMF belonging to the genus Glomus were isolated. The %AMF colonization in the mangrove plants was between 0 and 17%, and the presence of AMF in the aerenchymatous
cortex suggests that the mangrove plants may be aiding in AMF survival by providing oxygen. Two strains of phosphate solubilising
Pseudomonas aeruginosa were found in the mangrove soils of Great Nicobar. Phosphate solubilisation by the two isolated strains was almost 70% under
in vitro conditions. PSB may play a role in the mangrove ecosystems of Great Nicobar by mobilising insoluble phosphate. The
plant roots could pick up the released phosphate directly or with the aid of AMF hyphae.
Biology and Fertility of Soils 04/2012; 42(4):358-361. · 2.32 Impact Factor
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ABSTRACT: Two psychrotrophic strains ofRhizobium, DDSS69, a non-cold acclimated strain, and ATRI, a cold acclimated strain, were subjected to cold stress. A 4-fold increase
in the specific activity of lactate dehydrogenase (LDH) was characteristic for cold stressed cells of DDSS69, whereas ATR1
showed a higher LDH activity in general, which increased 1.5-fold under cold stress. Cold sensitive mutants of DDSS69 which
could not grow below 15°C, in contrast to the wild type which could grow at 5°C, were isolated using Tn5-tagged mutagenesis.
These mutants showed a 40% lower LDH activity than the wild type grown at 5°C that was comparable to the wild type grown at
15°C. High specific activity of succinic dehydrogenase (SDH) at 28°C in both strains and mutants indicated that aerobic respirationvia the citrate cycle is the normal mode of saccharide utilization. Shifts to lower temperatures decreased the specific activity
of SDH. However, alcohol dehydrogenase (ADH) activity remained very low in both the strains and the mutants at low temperatures
indicating that a shift from aerobic saccharide metabolism to anaerobic one under cold stress involves lactate glycolysis
rather than alcohol fermentation. There was an increase in membrane-bound ATPase activity under cold stress which is correlated
to higher LDH activity. These data show that, in psychrotrophicRhizobium strains, cold stress induces a switchover of respiratory metabolism from aerobic to anaerobic pathway, especially lactate
glycolysis.
Folia Microbiologica 04/2012; 45(2):177-182. · 0.68 Impact Factor
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ABSTRACT: A novel serine protease inhibitor (AmPI) was purified from larval hemolymph of tasar silkworm, Antheraea mylitta by two-step process of trypsin-affinity and gel-filtration (FPLC) chromatography. AmPI was active against larval midgut and commercial bovine trypsin and chymotrypsin. The extent of purification was determined by SDS and Native PAGE. The protease inhibitor had an apparent molecular weight of approximately 14.5 kDa as determined by SDS-PAGE. Its activity was stable over a pH range of 4.5-9 and temperatures range of 4-65 degrees C. Molecular weight as determined by MALDITOF-MS was between 13241.63 and 13261.66 Da. MS profile of AmPI also suggests two isoforms of AmPI because of glycosylation by heptose (C(7)H(14)O(7)). This confirmed the result of Native PAGE showing two bands. N-terminal amino acid sequence of this protein did not show similarity to any known protease inhibitor. To study the functional implications of AmPI in insect, it was localized in insect body tissue of different larval instars by immunogold labeling technique using GAR-gold conjugate as secondary antibody. The pattern of localization suggests constitutive nature of AmPI, which may have role in insect's defense mechanism.
Peptides 09/2009; 31(3):474-81. · 2.43 Impact Factor
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ABSTRACT: Extracts of roots of Rumex nepalensis, Berberis aristata, Arnebia benthamii, bark of Taxus wallichiana, Juglans regia and petals of Jacquinia ruscifolia were tested for their antifungal activity against twelve different fungal pathogens. Ethanolic extracts of R. nepalensis and J. ruscifolia extracts showed a broad spectrum of activity.
Fitoterapia 08/2008; 79(7-8):589-91. · 1.85 Impact Factor
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Fitoterapia. 01/2008; 79:589-591.
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ABSTRACT: The roles of serine proteases involved in the digestion mechanism of the cutworm Spodoptera litura (Lepidoptera: Noctuidae) were examined (in vitro and in vivo) following feeding of plant protease inhibitors. A trypsin inhibitor from Archidendron ellipticum (AeTI) was purified by ammonium sulfate fractionation, ion-exchange chromatography and size-exclusion chromatography (HPLC) and its bioinsecticidal properties against S. litura were compared with Soybean Kunitz trypsin inhibitor (SBTI). AeTI inhibited the trypsin-like activities of the midgut proteases of fifth instar larvae of S. litura by over 70%. Dixon plot analysis revealed competitive inhibition of larval midgut trypsin and chymotrypsin by AeTI, with an inhibition constant (K(i)) of 3.5x10(-9) M and 1.5x10(-9) M, respectively. However, inhibitor kinetics using double reciprocal plots for both trypsin and chymotrypsin inhibitions demonstrated a mixed inhibition pattern. Feeding experiments conducted on different (neonate to ultimate) instars suggested a dose-dependent decrease for both the larval body weight as well as % survival of larva fed on diet containing 50, 100 and 150 microM AeTI. Influence of AeTI on the larval gut physiology indicated a 7-fold decrease of trypsin-like protease activity and a 5-fold increase of chymotrypsin-like protease activity, after being fed with a diet supplemented with 150 microM AeTI. This study suggests that although the early (1st to 3rd) larval instars of S. litura are susceptible to the trypsin inhibitory action of AeTI, the later instars may facilitate the development of new serine proteases, insensitive to the inhibitor.
Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology 06/2007; 145(4):669-77. · 2.62 Impact Factor
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ABSTRACT: A Kunitz proteinase inhibitor from Archidendron ellipticum seeds (AeTI) was purified and complexed with bovine trypsin and chymotrypsin. The stoichiometric stability of AeTI with its interacting proteinases was then investigated using spectrophotometric, size exclusion chromatography (HPLC system), Western blotting and circular dichroism (CD) studies. All the methods were remarkably similar in revealing the preference of trypsin over chymotrypsin by AeTI for complex formation. Both Western blotting as well as spectrophotometry based assays for competition experiments indicated that trypsin displaces chymotrypsin from a previously formed AeTI–chymotrypsin complex. Chemical modification of lysine and arginine by TNBS and CHD treatments, respectively, suggested a lysine as the active site residue and also indicated the presence of a single protease-binding site for AeTI. CD of native AeTI showed a sharp minimum at 200 nm and deconvolution of the CD spectra revealed it to be an unordered protein possessing high β-sheet content. Complex formation of AeTI with trypsin induces a fractional switchover of its unordered structure towards the β-sheet fraction but lacked any such conversion in the presence of chymotrypsin. Prolonged exposure of excess trypsin generates conformational modifications both in the secondary and the tertiary structures.
Plant Physiology and Biochemistry 01/2006; 44(11-12-44 (11-12)):637-644. · 2.84 Impact Factor
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ABSTRACT: Mistletoe ribosome inactivating proteins (RIPs) are excellent immunomodulators obtained from a hemi-parasitic plant Viscum album L. In the present study, we have characterized and cloned a 65 kDa heterodimeric RIP from Himalayan V. album. Himalayan mistletoe ribosome inactivating protein (HmRIP) possessed unique sugar affinity for l-Rhamnose, Meso-inositol and l-Arabinose besides Galactose and N-acetyl-Galactosamine. The lectin activity was stable to a broad range of temperature (4–65 °C) and pH (2.5–12.5). cDNA cloning showed that HmRIP is 500 amino acids long and shortest among mistletoe RIPs. Amino acid sequence analyses revealed important differences at the functionally significant sites. In the lectin subunit, two critical residues forming base of the 2γ sugar-binding cleft were deleted. Such differences lead to a different conformation of sugar-binding cleft giving rise to unique sugar-binding properties of HmRIP. Toxin subunit also showed a sizeable deletion of four residue segment in the antigenic epitope (83–103) determining its antigenecity. Due to striking differences at the functional sites associated with medicinal properties, HmRIP is a novel type II RIP. In the phylogenetic tree based on amino acid sequence of type II RIPs from six dicot families, mistletoe RIPs branched out from the RIPs of all other taxa and formed a distinct and distant group supporting independent evolution of Viscaceae among the angiosperms.
Plant Science. 01/2005;
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ABSTRACT: Exposure of healthy wheat seeds (Triticum aestivum var Sonalika) to mild dose of cadmium (Cd(2+)) given as 50 microM CdCl(2) for 48 h and then washed off Cd(2+) offered resistance to the subsequent infection by Fusarium oxysporum inoculum. Seven days old seedlings having two primary leaves were aseptically inoculated with fungus, F. oxysporum (1 x 10(6)) spores. The seedlings pre-exposed to low level of Cd(2+) survived the Fusarium infection, while plantlets without Cd(2+) stress wilted and then perished due to Fusarium infection. The stress associated proteins induced by Cd(2+) (50 microM), F. oxysporum and by the co-stress (50 microM Cd(2+) and then with F. oxysporum) treatments were observed to be of same molecular weight (51 kDa). Antibody was raised against the purified Cd(2+)-stress associated protein (CSAP). Immuno-gold labeling of wheat seedling root tissue showed the presence of this CSAP in Cd(2+) pre-exposed and in co-stressed tissues and to be located predominantly on the inner linings of the cell membranes. We also observed that the anti-CSAP-antibody also labeled the root tissue of only Fusarium inoculated seedlings and the gold labeling was intensely located on the membrane. This cross-reaction of anti-CSAP suggests that Fusarium-induced stress protein (FISP) possibly has close homology to CSAP. We thus show for the first time the over expression of a high molecular mass protein by mild dose of Cd(2+) pre-exposure to wheat seeds which subsequently provided protection against Fusarium infection. This mode of resistance developed by an abiotic stress-causing agent against pathogen infection is novel.
Plant Physiology and Biochemistry 01/2005; 42(10):781-7. · 2.84 Impact Factor
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Chemistry & Biodiversity,. 01/2005; 2(4):429-446.
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Asian J. Chem. 01/2005; 17(1):149-154.
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Journal of Medical Microbiology 10/2003; 52(Pt 9):843. · 2.50 Impact Factor
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ABSTRACT: Plant root mucilage is known to enhance soil quality by contributing towards the soil carbon pool, soil aggregation, detoxification of heavy metal ions and interactions with rhizospheric microflora. Mucilage consists of many monosaccharide units, including fucose which can be used as an indicator for plant root based polysaccharides. This is the first report of an immunological technique developed to use anti-fucose antibodies as markers for probing and localizing fucosyl residues in mucilage polysaccharide and, in turn, for localization of plant root mucilage. Fucose was complexed with bovine serum albumin to raise antibodies against fucose. A fucose-directed antibody was shown to cross-react with root cap mucilages from grasses. This antibody was used to localize root mucilage polysaccharide in maize and wheat root caps using immunogold electron microscopy. Abundant labelling could be localized on the cell wall, and in the intercellular matrix and vesicles of the peripheral root cap cells. Labelling was less intense in cells towards the centre of the root cap tissue. Control experiments confirmed that immunogold localization of fucose was specific and reliable.
Annals of Botany 04/2002; 89(3):293-9. · 4.03 Impact Factor
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ABSTRACT: Plasmid genotypes of root nodulating rhizobial isolates of Sesbania, sampled from six ecologically distinct habitats, were characterized. Plasmid profile analysis revealed nine different plasmid types having molecular masses ranging from 30 to 300 MDa, distributed among six profile types that grouped the isolates into six plasmid classes. The six plasmid profiles were diverged from each other and lack many common plasmid types among them. Variation in number and types of symbiotic (Sym) plasmid was assessed by hybridization of plasmid profiles with sym gene probes. Relatedness among different plasmid types was assessed by hybridization of total DNAs as well as plasmid profiles of different isolates with labelled intact plasmid. Plasticity of plasmid genotype and possible recombination between different plasmid types is suggested from the results obtained. Structural diversity among sym plasmids was assessed by PCR amplified product profiles using primer corresponding to the reiterated nif promoter consensus element (NPC-PCR). A total of 26 NPC-PCR profile types were recognized. Genetic diversity among sym plasmids of isolates belonging to the same plasmid class and having similar sym plasmid suggested recombinations and rearrangements of sequences within the sym plasmids. Cluster analysis based upon similarity among profile types sorted the isolates across the ecological gradient. We suggest that habitat heterogeneity and plasticity of plasmid genotype together contribute for the generation of genetic diversity leading to strainal differentiation in rhizobia.
FEMS Microbiology Letters 01/2002; 205(2):171-8. · 2.04 Impact Factor
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Soil Biology and Biochemistry 01/2002; 34:965-. · 3.50 Impact Factor
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ABSTRACT: Non-compliance by patients and poor clinical management due to the use of incorrect regimens are the main reasons for the development of drug resistance by mycobacterial strains. New strategies for the control of multi-drug-resistant mycobacterial strains have become a necessity for proper management of tuberculosis, which, according to the WHO report (1997), is estimated to remain among the top 10 mortality-causing diseases of the twenty-first century. One of the strategies is the use of iron-sequestering agents like siderophores as active therapeutic agents in the treatment of tuberculosis. This report describes for the first time the inhibition of the growth of Mycobacterium tuberculosis H37Ra in vitro by a phytosiderophore isolated from the root washings of Tephrosia purpurea. This finding may help in the establishment of a new drug regimen which will be more effective in the treatment of tuberculosis.
Journal of Medical Microbiology 11/2001; 50(10):916-8. · 2.50 Impact Factor
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ABSTRACT: Cold stress induces a lag phase in the growth cycle of Rhizobium DDSS69. Two cold sensitive mutants of DDSS69 were generated through Tn5 tagged mutagenesis. These mutants do not grow below 15 degrees C but show a growth curve comparable with the wild type grown at 5 degrees C. There is a rapid induction of two high molecular weight membrane polypeptides of 135 and 119 kDa within 15 min of exposure to 5 degrees C in DDSS69. PAGE membrane protein profiles of stressed and non-stressed cells reveal differential regulation of genes. At 15 degrees C both mutants lack the high molecular weight polypeptides, suggesting a role in alleviation of cold stress.
Microbiological Research 02/2001; 156(3):279-84. · 2.31 Impact Factor
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ABSTRACT: Cold stress resulted in a decrease in the poly-beta-hydroxybutyrate (PHB) content of non-cold-acclimated Rhizobium DDSS69 cultures. Analysis of the specific activity of beta-ketothiolase and beta-hydroxybutyrate dehydrogenase revealed that decrease in PHB levels was a result of the inhibition of synthesis of PHB rather than an increase in its breakdown. Rhizobium ATR1, a cold-acclimated strain, revealed the presence of a stable PHB metabolism that did not show any significant differences either in PHB levels or in the activity of enzymes of the PHB metabolism under cold stress, suggesting that PHB is not involved in cold tolerance. Analysis of specific activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of the pentose phosphate pathway showed the upward regulation of alternate pathways of carbohydrate metabolism under cold stress to rapidly generate energy to overcome the stress. There is diversity in the switching mechanisms of carbon metabolism among cold-acclimated and non-cold-acclimated Rhizobium isolates. Upward regulation of malate dehydrogenase in both isolates suggests that it is a critical input for cold tolerance.
Current Microbiology 02/2001; 42(1):53-8. · 1.82 Impact Factor
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ABSTRACT: Two psychrotrophic strains of Rhizobium, DDSS69, a non-cold acclimated strain, and ATR1, a cold acclimated strain, were subjected to cold stress. A 4-fold increase in the specific activity of lactate dehydrogenase (LDH) was characteristic for cold stressed cells of DDSS69, whereas ATR1 showed a higher LDH activity in general, which increased 1.5-fold under cold stress. Cold sensitive mutants of DDSS69 which could not grow below 15 degrees C, in contrast to the wild type which could grow at 5 degrees C, were isolated using Tn5-tagged mutagenesis. These mutants showed a 40% lower LDH activity than the wild type grown at 5 degrees C that was comparable to the wild type grown at 15 degrees C. High specific activity of succinic dehydrogenase (SDH) at 28 degrees C in both strains and mutants indicated that aerobic respiration via the citrate cycle is the normal mode of saccharide utilization. Shifts to lower temperatures decreased the specific activity of SDH. However, alcohol dehydrogenase (ADH) activity remained very low in both the strains and the mutants at low temperatures indicating that a shift from aerobic saccharide metabolism to anaerobic one under cold stress involves lactate glycolysis rather than alcohol fermentation. There was an increase in membrane-bound ATPase activity under cold stress which is correlated to higher LDH activity. These data show that, in psychrotrophic Rhizobium strains, cold stress induces a switchover of respiratory metabolism from aerobic to anaerobic pathway, especially lactate glycolysis.
Folia Microbiologica 02/2000; 45(2):177-82. · 0.68 Impact Factor
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ABSTRACT: We have used RT PCR and 3'RACE to identify diverse serine proteinase genes expressed in the midguts of the rice yellow stem borer (Scirpophaga incertulas) and Asian corn borer (Helicoverpa armigera). The RT-PCR primers encoded the conserved regions around the active site histidine57 and serine195 of Drosophila melanogaster alpha trypsin, including aspartate189 of the specificity pocket. These primers amplified three transcripts (SiP1-3) from midguts of S. incertulas, and two transcripts (HaP1-2) from midguts of H. armigera. The five RT PCR products were sequenced to permit design of gene-specific forward primers for use with anchored oligo dT primers in 3'RACE. Sequencing of the 3'RACE products indicated that SiP1, SiP2 and HaP1 encoded trypsin-like serine proteinases, while HaP2 encoded a chymotrypsin-like serine proteinases. The SiP3 transcript proved to be an abundant 960 nt mRNA encoding a trypsin-like protein in which the active site serine195 was replaced by aspartate. The possible functions of this unusual protein are discussed.
Insect Biochemistry and Molecular Biology 02/2000; 30(1):57-68. · 3.25 Impact Factor
