Differences between aquatic and soil N2-fixing Cyanobacteria in relation to nitrogen compounds metabolism
1997
Svircev, Z.B. | Gajin, S.K. | Matavulj, M.N. | Stojkovic, S.S. (University of Novi Sad, Novi Sad (Yugoslavia). Institute of Biology)
Heterocystous Cyanobacteria are the group of N2-fixing photosynthetic prokaryotes, that have an important role of nitrogen balance in aquatic and soil ecosystems. In this paper we present N2-fixing and excretion characteristics of six strains (Nostoc and Anabaena genus) isolated from soil, and aquatic samples. According to the results of the acetylene reduction, which indicate the ability of the atmospheric nitrogen intake, three soil isolates have even 16 times higher activity of the nitrogenase related to the three aquatic isolates. In conditions without combined nitrogen, aquatic isolates do not excrete the ammonium, while the soil strains show significant specific production of ammonium. The ability of aminoacids and proteins discharging has been observed in culture with aquatic strains, but statistically significant higher production of these compounds was determined only in soil strains. At the same time the percentage of heterocysts, as the place of nitrogenase activity, is not significantly different between soil and aquatic isolates, leading to the conclusion that physiological differences are not the result of heterocysts differentiation, but the consequence of physiological and biochemical changes specific to the ecology of the strains.
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