INTERACTION OF PHOTOSYNTHESIS AND NITROGEN METABOLISM IN ACID STRESS TOLERANCE OF NOSTOC sp.
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Date
2019
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DIVISION OF Microbiology ICAR- INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Low pH tolerant Nostoc strains grown under control (pH 7.0) and low pH (pH 4.5)
conditions, and fresh water strain Nostoc punctiforme, grown in medium having pH
7.0, in absence or presence of nitrogen or carbon supplementation, were used to
study growth and physiological parameters during exponential phase of growth.
Comparative study amongst selected Nostoc strains under control pH (7.0)
and low pH (4.5) medium indicated a significant and variable influence of nitrogen
or carbon supplementation for specific traits. The chlorophyll content was not
influenced by supplementation, while, total soluble proteins exhibited a variable
pattern with N supplementation, and was reduced with carbon supplementation.
Extracellular ammonia release was higher without supplementation as compared to
supplemented medium. Intracellular sucrose remained more or less similar under
three conditions at pH 7.0, while under low pH, supplementation showed an
enhancement. Supplementation of medium increased oxygen evolution rate, and
Fv/Fm ratio without or with N indicated varied response, whereas Fv/Fm ratio was
reduced with carbon supplementation. Carbon supplementation in the medium
enhanced nitrogenase activity several folds and nitrate reductase activity enhanced
significantly with nitrogen supplementation as compared to un-supplemented
medium under pH 7.0 or 4.5. Carbon supplementation in the medium did not have
much impact on nitrate reductase activity. Nitrite reductase activity enhanced with N
or C supplementation, while the activity of glutamine synthetase depicted differential
response under two pH growing conditions. Proline content and lipid peroxidation
was higher in cultures in absence of N or C supplementation as compared to the
supplemented medium, whereas glycerol content was increased with nitrogen and
decreased with C supplementation. Glycine betaine remained more or less similar
under un-supplemented or supplemented medium of pH 7.0 or pH 4.5.
Activities of superoxide dismutase and catalase were higher under unsupplemented medium as compared to cultures grown in medium having N or C
supplementation. Catalase and ascorbate peroxidase activity also showed reduction
when the medium was supplemented with N or C as compared to un-supplemented
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medium. Statistical analysis indicated that the interactive effect was significant for
most of the selected parameters. Calculation for Principal Components Analysis was
done and the total % variance contributed by first four Principal Components
accounted for 96 %. Principal Components (PC1 and PC2) contributed positively
under some situations and negatively under others. Combined analyses of PC1-PC4
confirmed the individual analyses and clustering treatments in the same trend.
Pearson correlation coefficients analyses based on p value showed different levels of
correlation amongst selected parameters studied under two cultural conditions and
cluster analysis indicated trait variation amongst Nostoc cultures. Gene expression
study for nifH and rbcL gave variable results by low pH tolerant strains under two
conditions of growing medium (pH 7.0; pH 4.5). Studies conducted clearly indicated
complexity of abiotic stress mechanism involving morpho-physiological and genetic
attributes in cyanobacteria.
Description
T-10073
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