NITRATE REDUCTASE ACTIVITY OF SULPHATE-REDUCING BACTERIA Desulfomicrobium SP. CRR3 AT THE DIFFERENT CONDITIONS OF THE CULTIVATION

97 Sulphate-reducing bacteria are unique group of microorganisms that are able to use various inorganic compounds including sulphate and nitrate as terminal electron acceptors during the obtaining energy. This exact feature is of considerable interest in studying mechanisms of nitrate reduction activity of sulphate-reducing bacteria. Nitrate reduction is widely spread among prokaryotes and described in few sulphatereducing bacteria, particularly in the genera of Desulfovibrio [1, 2], Desulfomonas [1] and others. High concentrations of nitrates inhibit sulfate reduction [2, 3]. Nitrate reductase (EC 1.6.6.2; NR) is a key enzyme of nitrate reduction with molibdopterynguaninedinucleotide that is a part of the active site [4]. It belongs to dymethylsulphoxydreductase and is found both in eukaryotic and in prokaryotic organisms and plays an important role in converting nitrogen compounds [1]. Depending on its location and function in cells of microorganisms cytoplasmic assimilatory nitrate reductase (NAS), periplasmic dissimilatory nitrate reductase (NAP) and dissimilatory membrane nitrate reductase (NAR) are described [4]. For the first time the presence of nitrate reductase in sulphate-reducing bacteria Desulfovibrio desulfuricans ATCC 27774 was shown by Bursakov and others. [5]. Some features of reduction of sulphates into the representatives of the genus of Desulfomicrobium at the presence of nitrates are described in the works of Sholyak and Dorosh [2, 3]. The aim of this work was to investigate nitrate reductase activity of sulphate-reducing bacteria Desulfomicrobium sp. CrR3 under the different culture conditions.