Browsing by Author "Sureshwar P. Singh"

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Antibacterial potential of γ-linolenic acid from Fischerella sp. colonizing Neem tree bark
(2006) Ravi K. Asthana; Arunima Srivastava; Arvind M. Kayastha; Gopal Nath; Sureshwar P. Singh
Pharmaceutically important γ-linolenic acid (GLA) was produced (4.1 mg g-1 dry wt) by laboratory grown cyanobacterium Fischerella sp. colonizing Neem (Azadirachta indica) tree bark. GLA isolated from the test cyanobacterium was active against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25992, Salmonella typhi (local strain), Pseudomonas aeruginosa ATCC 27853 and Enterobacter aerogenes MTCC 2822. The overproduction of GLA was also monitored by altering phosphate and nitrate levels in the nutrient medium. A doubling in phosphate concentration (58 μM) increased GLA level up to 12% over that of control cells while half of this phosphate level reduced GLA synthesis by 8%. In contrast, elevated nitrate concentrations (5 and 10 mM) stimulated biomass yield but not GLA, as the levels approximated to the nitrate-lacking control. The antibacterial potential of GLA from Fischerella sp. grown at varying P or N levels was at variance as evidenced by the diameter of inhibition zones against S. aureus. This variation in inhibition zones reflected differing levels of GLA as ascertained quantitatively by HPLC. © Springer 2005.
Heavy and trace metals in carcinoma of the gallbladder
(2013) Somprakas Basu; Manish K. Singh; Tej B. Singh; Satyanam K. Bhartiya; Sureshwar P. Singh; Vijay K. Shukla
Background: Carcinoma of the gallbladder is the commonest malignancy of the biliary tract in northern India The etiologic relation of specific metals (heavy and trace) and their compounds to neoplasia has been a topic of investigation for some time but not adequately described for carcinoma of the gallbladder. The aim of the present study was to evaluate the relation of heavy and trace metals to this malignancy. Methods: The levels of selenium, zinc, copper, manganese, cadmium, chromium, lead, and nickel were estimated in serum, bile, gallstones, and gallbladder tissue using atomic absorption spectrophotometry. The tests were carried out in 30 patients with gallbladder cancer and 30 sex-matched patients with cholelithiasis. Results: Selenium and zinc levels were significantly reduced (p < 0.001) and copper concentration was found to be significantly higher (p < 0.001) in serum, bile, and gallbladder tissue from patients with carcinoma of the gallbladder. Lead, cadmium, chromium, and nickel levels were elevated in serum and bile in patients with carcinoma of the gallbladder. Conclusions: The present study demonstrated a significant decrease in serum, biliary, and tissue levels of selenium and zinc but increased copper, lead, cadmium, chromium, and nickel levels in patients with carcinoma of the gallbladder, indicating a strong relation between the concentrations of these metals and gallbladder cancer. © 2013 Société Internationale de Chirurgie.
Identification of an antimicrobial entity from the cyanobacterium Fischerella sp. isolated from bark of Azadirachta indica (Neem) tree
(2006) Ravi K. Asthana; Arunima Srivastava; Akhilesh P. Singh; Deepali; Sureshwar P. Singh; Gopal Nath; Ranjana Srivastava; Brahm S. Srivastava
The active principle in a methanolic extract of the laboratory-grown cyanobacterium, Fischerella sp. isolated from Neem (Azadirachta indica) tree bark was active against Mycobacterium tuberculosis, Enterobacter aerogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli as well as three multi-drug resistant E. coli strains in in vitro assays. Based on MS, UV, IR 1H NMR analyses the active principle is proposed to be hapalindole T having the empirical formula C21H 23N2ClSO and a molecular weight of 386 with the melting point range 179-182°C. The estimated production of Hapalindole T from the cyanobacterium is 1.25 mg g-1 lyophilized biomass. It is suggested that cyanobacteria colonizing specialized niches such as tree bark could be an antibacterial drug resource. © Springer 2006.
Identification of maltooligosyltrehalose synthase and maltooligosyltrehalose trehalohydrolase enzymes catalysing trehalose biosynthesis in Anabaena 7120 exposed to NaCl stress
(Elsevier GmbH, 2005) Ravi K. Asthana; Subhasha Srivastava; Akhilesh P. Singh; Arvind M. Kayastha; Sureshwar P. Singh
Anabaena 7120 cells were exposed to NaCl (25-175 mM) stress. Maximum growth was recorded in media containing 150 mM NaCl. Short-term exposure (48 h) of the cyanobacterial biomass to 150 mM NaCl, induced highest trehalose level (37 mM). Control cells lacking NaCl did not show any trace of trehalose as ascertained by NMR and HPLC analysis. Trehalose biosynthesis observed with NaCl plus high temperature (40°C) indicated that its production was specifically triggered by NaCl, not temperature. The increase in trehalose level during NaCl stress was the result of overexpression of the trehalose-forming enzymes maltooligosyltrehalose synthase (MTSase), EC 5.4.99.15 (114 kDa) and maltooligosyltrehalose trehalohydrolase (MTHase), EC 3.2.1.141 (68 kDa) as evidenced by SDS-PAGE analysis. To our knowledge this is the first report of induced trehalose biosynthesis in Anabaena 7120 during salt-stress, accompanied by identification of MTSase and MTHase enzymes on gel. It is suggested that Anabaena 7120 cells synthesize the osmolyte trehalose to withstand osmotic fluctuations. © 2005 Elsevier GmbH. All rights reserved.
Isolation and identification of a new antibacterial entity from the Antarctic cyanobacterium Nostoc CCC 537
(2009) Ravi K. Asthana; Deepali; Manoj K. Tripathi; Arunima Srivastava; Akhilesh P. Singh; Sureshwar P. Singh; Gopal Nath; Ranjana Srivastava; Brahm S. Srivastava
The present study was aimed at the isolation, purification and structural elucidation of an antibacterial entity/lead molecule from the Antarctic cyanobacterium Nostoc CCC 537. A methanolic extract of the cyanobacterium was bioassayed with Enterobacter aerogenes as a target. The extract was purified by TLC, and the most active band was subjected to HPLC. The fraction (retention time 15.7 min) designated as the active principle was antibacterial towards Gram positive Mycobacterium tuberculosis H37Rv, Staphylococcus aureus ATCC 25923, Gram negative Salmonella typhi MTCC 3216, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25992, Enterobacter aerogenes MTCC 2822 and multi-drug resistant strains of Escherichia coli GS 2003/01, 02, 03. Based on UV, IR, 1H NMR, EIMS, and ESIMS data, the structure of the active principle is proposed as 4-[(5-carboxy-2-hydroxy)-benzyl]-1,10-dihydroxy-3,4,7,11,11- pentamethyloctahydrocyclopentanaphthalene (Mr 428, Mp 243-249°C). This intracellular biomolecule is similar to anthraquinone and indane derivatives of a diterpenoid. The rate of production of the active principle currently corresponds to 1.70 mg g-1 biomass dry weight. The inherent property of Nostoc sp. to synthesise niche-specific biomolecules/lead molecules may be exploited for future drug development. © 2008 Springer Science+Business Media B.V.
Nickel uptake by Pseudomonas aeruginosa: Role of modifying factors
(1998) Pinaki Sar; Sufia K. Kazy; Ravi K. Asthana; Sureshwar P. Singh
Pseudomonas aeruginosa cells growing in minimal medium were 40-fold more sensitive to Ni2+ than cells growing in enriched medium, suggesting a possible protective role of medium ingredients. Likewise, cells pre-grown in enriched medium showed a high K(m) (6.15 mM) and increased Ni2+ uptake (950 nmol mg-1 protein, 1h) over cells pre-sown in minimal medium (K(m), 0.48 mM: 146 nmol mg-1 protein, 1 h). The overall pattern indicates that cells pre-grown in enriched medium were characterized by having lowered affinity towards Ni2+ than those with minimal medium background. The enhanced Ni2+ uptake by enriched medium-grown cells can be correlated with the improved metabolic state of the cells Ni2+ uptake was optimum at neutrality (pH 7.0). A major Ni2+ transport system was competitively inhibited by Mg2+, Zn2+, Cd2+, or Co2+ (400 μM each). Noticeably, a minor Ni2+ transport pathway was still operative even in the higher concentration range of Mg2+ (4 mM and 40 mM). The stimulation of Ni2+ uptake monitored in the presence of different carbon sources (0.5% wt/vol, each) showed the sequence: glucose (1.6-fold) > phenol = gallic acid (1.5 fold). Succinate, in comparison, reduced Ni2+ uptake (0.5-fold) possibly because of its acting as a metal chelator as well. Sensitivity of Ni2+ transport towards methyl viologen, azide, 2-4 DNP, and DCCD suggested that transport was energy- linked.
Trehalose-producing enzymes MTSase and MTHase in Anabaena 7120 under NaCl stress
(2008) Ravi K. Asthana; Subhasha Nigam; Archana Maurya; Arvind M. Kayastha; Sureshwar P. Singh
Salt tolerance, a multigenic trait, necessitates knowledge about biosynthesis and function of candidate gene(s) at the cellular level. Among the osmolytes, trehalose biosynthesis in cyanobacteria facing NaCl stress is little understood. Anabaena 7120 filaments exposed to 150 mm NaCl fragmented and recovered on transfer to -NaCl medium with the increased heterocysts frequency (7%) over the control (4%). Cells failed to retain Na+ beyond a threshold [2.19 mm/cm3 (PCV)]. Whereas NaCl-stressed cells exhibited a marginal rise in K+ (1.1-fold) only at 30 h, for Na+ it was 130-fold at 48 h over cells in control. A time-course study (0-54 h) revealed reduction in intracellular Na+ beyond 48 h [0.80 mm/cm 3 (PCV)] suggestive of ion efflux. The NaCl-stressed cells showed differential expression of maltooligosyltrehalose synthase (MTSase; EC 5.4.99.15) and maltooligosyltrehalose trehalohydrolase (MTHase; EC 3.2.1.141) depending on the time and the extent of intracellular Na+ buildup. © 2008 Springer Science+Business Media, LLC.