Evidence for a sodium-dependent proline and glycine-betaine uptake in the cyanobacterium <Emphasis Type="Italic">Nostoc muscorum</Emphasis> |
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Authors: | S Bhargava R K Kachouli R Maithil V Kaithwas |
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Institution: | 1.Division of Microbiology, Department of Botany,Government Motilal Science College,Bhopal,India |
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Abstract: | The cyanobacterium Nostoc muscorum is able to utilized proline and glycine-betaine as a nitrogen source under unstressed growth conditions. This cyanobacterium
when grow in modified Chu No. 10 medium (without Na+) unable to utilized proline and glycine-betaine as a nitrogen source. Spontaneously occurring mutant clones defective in
Na+ transport (Na+-R) was isolated and analyzed for proline and glycine-betaine utilization. The mutant phenotype showed normal heterocyst frequency
and nitrogenase activity even in the medium containing 1 mM proline or 1 mM glycine-betaine, indicates the role of Na+ for proline/glycine-betaine uptake. The Na+-R mutant showed 100% survival at pH 11 and was simultaneously able to uptake and utilize proline/glycine-betaine at higher
alkaline pH. This indicates that proline and glycinebetaine uptake systems are more efficient at higher alkaline pH. Since,
the hypersaline environments are rich in Na+ contents and have alkaline pH, therefore it is suggested that the origin and evolution of specific compatible solutes may
not depend only on the osmoregulatory role they play, but also on the other ecological factors operating simultaneously in
the organism’s niche. |
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