Effect of lead on nitrogenase and enzymes of nitrogen assimilation in a cyanobacterium Nostoc muscorum.
Lead decreased the growth rates, total cell mass, heterocyst frequency, total cell protein, nitrogenase activity, glutamine synthetase (GS) and glutamate synthase (GOGAT) activities in N:muscorum. However, lead at 0.01 and 10 micrograms ml-1 conc. enhanced nitrogenase as well as GS activity of the cells. On transfer to excess lead (100 micrograms ml-1), nitrogenase and GS activities ceased almost after 24 hr in the cyanobacterium. It is deduced that lead has a two step effect on stimulation and inhibition of metabolic activity at 0.01 and 10 micrograms ml-1 concentration and 0.1 and 100 micrograms ml-1 concentration respectively indicating a close interaction between nitrogen fixation and GS activity. However, GOGAT activity is an exception to this two step stimulation and inhibition process.
Trehan
K
K
Department of Botany, Kurukshetra University, India.
Maneesha
D000458:Cyanobacteria / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D005970:Glutamate Synthase / Q000378:metabolism; D007854:Lead / Q000494:pharmacology*; D009584:Nitrogen / Q000378:metabolism*; D009591:Nitrogenase / Q000187:drug effects / Q000378:metabolism*
D007854:Lead; D009591:Nitrogenase; D005970:Glutamate Synthase; D009584:Nitrogen