Browsing by Author "H.D. Kumar"

Now showing 1 - 20 of 74

Adaptation of a strain of Spirulina platensis to grow in cobalt‐and iodine‐enriched media
(1994) Y. Singh; H.D. Kumar
Cobalt‐ and iodide‐enriched (adapted, tolerant) strains of the protein‐rich cyanobacterium, Spirulina platensis, were produced by repeated sub‐culturing in increasing concentrations of the two trace elements. The strains enriched with cobalt and iodide showed higher uptake of these elements than the controls. The LD50 values for the parent and cobalt‐adapted strains were 95 and 231 μmol 1‐1 Co2+, respectively. Likewise, the LD50 values for parent and iodide‐adapted strains were 12 and 42 mmol‐1 I‐1. The carotenoid : chlorophyll a ratio of the parent strains increased after cobalt addition. The cobalt‐adapted strain showed a much higher ratio than the cobalt‐grown parent (sensitive) cells which remained unchanged after cobalt addition. Intracellular Co2+ uptake by the cells was concentration‐dependent and followed Michaelis‐Menten kinetics with saturation in uptake occurring in the parent and adapted strains at 126 and 189 μmol 1‐1 Co2, respectively. At saturating concentrations, the maximum Co2+ uptake was 39.73 and 158.43 nmol Co2+ mg‐1 protein, respectively for the parent and adapted strains. The adapted strain also showed greater cobalt adsorption. The Km of intracellular Co2+ uptake was lower in the case of adapted cells as compared with the parent, whereas Vmax showed an opposite trend. Thus, the adapted cells appear to be more efficient than the parent strain in intracellular uptake of cobalt. Differences between kinetic constants of both the strains suggest that the strains may be physiologically different. Likewise, iodide uptake was significantly higher in iodide‐adapted cells than in controls. Copyright © 1994, Wiley Blackwell. All rights reserved
Akinete formation and division in Anabaena oscillarioides (Cyanophyta, Nostocales)
(1989) A.S. Ahluwalia; H.D. Kumar
[No abstract available]
Algal growth as a means of evaluation of nutrient status of the effluent of a fertilizer factory near Shahupuri, Varanasi
(1976) L.C. Rai; H.D. Kumar
The nutrient status of the effluent of a fertilizer factory has been assayed by growing the unicellular green alga Chlorella sp. and the filamentous blue-green alga Anabaena doliolum as the test organisms. Nitrogen content was estimated by (a) growing Chlorella in different proportions of effluent and culture medium; (b) estimating the rate of NH4-N absorption in the dark by Chlorella cells previously grown in either surplus or limiting nitrogen conditions; and (c) comparing the heterocyst frequencies of Anabaena in nitrogen-free medium and in nitrogen free medium supplemented with effluent. The nutrient status as evaluated by algal assay agrees well with that determined by actual physico-chemical analysis of the effluent.
Canavanine-lnduced inhibition of growth and heterocyst differentiation in Anabaena doliolum and isolation of a canavanine-resistant mutant
(Springer India, 1981) A. Kumar; H.D. Kumar
The effect of the arginine analogue, canavanine on growth and heterocyst differentiation in the nitrogen-fixing alga Anabaena doliolum has been studied. The analogue inhibited growth and heterocyst differentiation at a concentration as low as 1 μM. The treated algal cells lacked conspicuous granular inclusions, whereas treatment with chloramphenicol led to increased synthesis of granules (probably cyanophycin granules). Exogenously added arginine completely reversed the effect of the analogue but lysine could only partially relieve the effect. A time course study with canavanine indicated inhibition of fresh protein(s) synthesis at all steps where a new class of proteins is synthesized so that the action of the analogue does not seem to be specific for a particular kind of protein. A mutant resistant to this analogue has been successfully isolated indicating that this alga does not show mutational immunity at least to the amino acid analogues unlike in the observation with different antibiotics. Our observations indicate that canavanine either directly inhibits protein synthesis or forms defective protein(s) which produces all the observed effects. © 1981 Indian Academy of Sciences.
Cellular differentiation and nitrogenase activity in the cyanobacterium Anabaena
(Springer Netherlands, 1982) A.S. Ahluwalia; H.D. Kumar
Nitrogenase activity at periods of differentiation of heterocysts and akinetes was assayed by the acetylene reduction technique. There was no nitrogenase activity in ammoniumgrown, non-heterocystous Anabaena sp.; the activity appeared only after a lag-phase of about 17 - 21 h after the ammonium-grown culture had been transferred to medium free of combined nitrogen. This activity started appearing as the proheterocysts were developing to mature heterocysts. Maximum nitrogenase activity was attained with exponential phase of culture and mature heterocysts. This activity gradually decreased with the differentiation of akinetes. Only insignificant nitrogenase activity was observed in old cultures in which most cells had matured into akinetes. © 1982 Academia.
Chromatic adaptation and photoreversal in blue-green alga Calothrix clavata West
(Springer India, 1980) A.S. Ahluwalia; R.K. Rai; H.D. Kumar
Complementary chromatic adaptation, a well-established phenomenon in some blue-green algae, has been observed in Calothrix clavata, a heterocystous blue-green alga of the family Rivulariaceae. The chromatic adaptation has been observed for fluorescent and incandescent light by measuring the absorption spectra. The material grown in fluorescent light forms more of phycoerythrin whereas more of phycocyanin tends to be formed in incandescent light. Besides this, photoreversal was observed by transferring the incandescent light grown alga to fluorescent light conditions and vice-versa. Effect of photoreversal and chromatic adaptation has also been discussed for this alga under different monochromatic light conditions. The influence of different light conditions on morphological changes, heterocysts and hormogonia formation has also been investigated. Both chromatic adaptation and photomorphogentic phenolmena in this alga show the involvement of some photoreversible (red:green) pigment. © 1980 Indian Academy of Sciences.
Copper toxicity in the fresh water cyanobacterium nostoc linckia
(1985) D. Kumar; M. Jha; H.D. Kumar
The effect of copper (CuC12.2H2O) on growth, heterocyst frequency, acetylene reduction, H2production and photosynthetic O2evolution of Nostoc linckia was studied. Whereas copper inhibited growth and other physiological processes, it increased heterocyst frequency and H2production. We conclude that copper pollution could considerably alter nitrogen dynamics in fresh water systems. © 1985, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.
DIFFERENTIAL EFFECT OF ULTRAVIOLET‐B RADIATION ON CERTAIN METABOLIC PROCESSES IN A CHROMATICALLY ADAPTING Nostoc
(1992) Rashmi Tyagi; G. Srinivas; Deepak Vyas; Ashok Kumar; H.D. Kumar
Abstract— The impact of UV‐B radiation on growth, pigmentation and certain physiological processes has been studied in a N2‐fixing chromatically adapting cyanobacterium, Nostoc spongiaeforme. A brownish form (phycoerythrin rich) was found to be more tolerant to UV‐B than the blue‐green (phycocyanin rich) form of N. spongiaeforme. Continuous exposure to UV‐B (5.5 W m‐2) for 90 min caused complete killing of the blue‐green strain whereas the brown strain showed complete loss of survival after 180 min. Pigment content was more strongly inhibited in the blue‐green strain than in the brown. Nitrogenase activity was completely abolished in both strains within 35 min of UV‐B treatment. Restoration of nitrogenase occurred upon transfer to fluorescent or incandescent light after a lag of 5–6 h, suggesting fresh synthesis of nitrogenase. Unlike the above processes, in vivo nitrate reductase activity was stimulated by UV‐B treatment, the degree of enhancement being significantly higher in the blue‐green strain. Like the effect of UV‐B on nitrogenase, 14CO2 uptake was also completely abolished by UV‐B treatment in both strains. Our findings suggest that UV‐B may produce a deleterious effect on several metabolic activities of cyanobacteria, especially in cells lacking phycoerythrin. Strains containing phycoerythrin appear to be more tolerant to UV‐B, probably because of their inherent property of adapting to a variety of light qualities. Copyright © 1992, Wiley Blackwell. All rights reserved
Differential effects of amino acid analogs on growth and heterocyst differentiation in two nitrogen-fixing blue-green algae
(1980) A. Kumar; H.D. Kumar
Effects of a few amino acid analogs on growth and heterocyst differentiation have been studied in two nitrogen-fixing species of Anabaena. All the analogs except α-methyl-dl-aspartic acid inhibited growth. Exposure of Anabaena doliolum, to dl-5-fluorotryptophan and dl-p-fluorophenylalanine caused pronounced fragmentation of filaments into single cells. At low concentrations (0.01 mM), α-methyl-dl-aspartic acid stimulated growth of the strain of A. doliolum as well as the strain of the second (unidentified)Anabaena species. Ethionine, dl-p-fluorophenylalanine, dl-5-fluorotryptophan, and canavanine blocked heterocyst differentiation, whereas α-methyl-dl-aspartic acid, α-methyl-dl-methionine, N-o-nitrophenylsulfenyl-l-tryptophan, norleucine, and S-2-aminoethyl-l-cysteine did not show any significant effect. Treatment with 7-azatryptophan, dl-β-hydroxynorvaline, l-methionine-dl-sulfoximine, l-methionine sulfone, and β-2-thienyl-dl-alanine led to a twofold increase in heterocyst frequency. Possible modes of action of the analogs in growth inhibition and changes in heterocyst frequency are discussed. © 1980 Springer-Verlag New York Inc.
Ecological studies on algae isolated from the effluents of an oil refinery, a fertilizer factory and a brewery
(1974) H.D. Kumar; G.P. Bisaria; L.M. Bhandari
The algal flora and physicochemical characteristics of the effluents of the Indian Oil Refinery, Barauni, the Sindri Fertilizer Factory, Sindri, and the Mohan Meakin Brewery, Ghaziabad were studied. The studies indicate that algae can tolerate and grow in highly polluted waters. The blue green algae, flagellates and euglenoids are mostly associated with organically rich effluents, low in dissolved oxygen, whereas waters rich in nitrogenous compounds favour the growth of green algae, e.g., Chlorella. A combination of algal and chemical characteristics may be successfully employed to evaluate the water quality of a given habitat.
Effect of 7-azatryptophan on heterocyst differentiation in Anabaena doliolum Bharadwaja
(1978) Manju Agrawal; H.D. Kumar
The effect of DL-7-azatryptophan, an analogue of tryptophan, has been studied on the heterocyst spacing pattern and the probability of proheterocyst regression in Anabaena doliolum. 7-azatryptophan suppressed growth and induced heterocyst differentiation in nitrogen-free medium. In ammonium (1 mM), nitrite (2 mM) and nitrate (2 mM) supplemented media, it caused proheterocyst regression with a frequency of 100%, 35% and 10% respectively. The role of azatryptophan in nitrogen metabolism has been discussed in relation to ammonia-uptake study. © 1978 Indian Academy of Sciences.
Effect of different nitrogen sources on growth and glycerol production by Dunaliella salina
(1999) A. Thakur; H.D. Kumar
The growth and glycerol production of Dunaliella salina was studied with substitution of various nitrogen sources in the medium. Potassium nitrate (10 mM) was found to be the best of several nitrogen sources tested followed by urea, ammonium nitrate, glycine, ammonium acetate and ammonium chloride. The photosynthesis, respiration, glycerol production and 14CO2 uptake rates were assessed in medium containing potassium nitrate and urea. Ultimately, KNO3 was found to be a better substrate than urea for ascertaining the growth and cellular contents of D. salina.
Effect of guanine nucleoside and nucleotides on growth and heterocyst differentiation in cyanobacteria
(1981) M. Bhattacharya; H.D. Kumar
[No abstract available]
Effect of pH and inorganic carbon concentration on growth, glycerol production, photosynthesis and dark respiration of Dunaliella salina
(2000) Archana Thakur; H.D. Kumar; Sudha M. Cowsik
The growth of Dunaliella salina was studied with respect to pH and varying concentrations of NaHCO3 in the medium. The growth rate, photosynthesis and dark respiration were maximal at pH 8 and 4 mM NaHCO3 in the medium. Photosystem I of the Hill reaction was affected more by inorganic carbon concentration than photosystem II.
Effect of some physiological factors on the nitrogenase and hydrogenase of the Azolla-Anabaena Azollae association
(1990) D. Kumar; A.B. Pandey; H.D. Kumar
Nitrogenase (acetylene reducing) activity, nitrogenase-mediated hydrogen evolution and hydrogenase-catalysed hydrogen uptake activity was studied in intact Azolla fronds. Nitrogenase activity was significantly influenced by various physiological parameters. When incubated under light, the rate of H2 evolved by the fronds under anaerobic conditions was significantly higher than that under aerobic condition. H2 uptake was significantly inhibited by both acetylene and carbon monoxide incubations. © 1990.
Effects of Aqueous Oil Extracts on Four Microalgae
(1985) J.P. Gaur; H.D. Kumar
[No abstract available]
Effects of cellular metabolism and viability on metal ion accumulation by cultured biomass from a bloom of the cyanobacterium Microcystis aeruginosa
(American Society for Microbiology, 1998) D.L. Parker; L.C. Rai; N. Mallick; P.K. Rai; H.D. Kumar
The sorption of nickel, cadmium, and copper by cultured biomass from a naturally occurring bloom of Microcystis aeruginosa was demonstrated in two systems: cells suspended in culture medium and cells immobilized in alginate. Incubation in the absence of light, in the presence of metabolic inhibitors, and at 4°C did not substantially decrease the copper accumulation by cells in culture medium. Heat-killed, formaldehydetreated, and air-dried biomass samples sorbed nearly as much (or in some cases slightly more) copper as did viable samples.
Effects of cyclic nucleotides on morphogenesis in Nostoc muscorum
(Springer-Verlag, 1978) H.D. Kumar; Manju Gupta
The filamentous cyanophyte Nostoc muscorum A grew aseriately in light in a mineral salts (sugar-free) culture medium supplemented with adenosine 3′:5′-cyclic-monophosphate or N6, O2-dibutyryl adenosine 3′:5′-cyclic-monophosphate (1 mM). The aseriate morphology thus formed in the light on the 10th day following inoculation was similar to that formed in the dark after 20-30 days growth in cAMP-free medium containing glucose or sucrose. Inoculum previously grown in sucrose- or glucose-containing medium displayed aseriate morphology with lesser proliferation of coccoid cells as compared to inoculum grown in the absence of glucose or sucrose. cGMP, ADP, AMP and inhibitors of phosphodiesterase (theophylline and caffeine) did not have any effect on the persistence of aseriate morphology. However they stimulated cell division at the aseriate stage and delayed the release of hormogonia. © 1978 Springer-Verlag.
Effects of different amino acids on growth and nitrogen fixation in Nostoc linckia
(1985) D.K. Mishra; M. Jha; H.D. Kumar
[No abstract available]
Effects of low temperature on two cyanobacteria
(1992) D. Kumar; J.B. Singh; H.D. Kumar
[No abstract available]