Molecular characterization and transcriptional regulation of nitrate reductase in a ruminal bacterium, Selenomonas ruminantium

The Journal of General and Applied Microbiology

Takahiro Yoshii¹  Miwa Iwamoto¹  Tsuneo Hino¹  Narito Asanuma¹ 

[1] Department of Life Science, College of Agriculture, Meiji University

关键词: nar gene;    nitrate reductase;    ruminal bacterium;    Selenomonas ruminantium;   

DOI  :  10.2323/jgam.50.55

学科分类：微生物学和免疫学

来源: Applied Microbiology, Molecular and Cellulrar Biosciences Research Foundation

【 摘 要 】

Nitrate reductase (NaR) of a strain of Selenomonas ruminantium was purified, and the gene encoding NaR (nar) was sequenced. The 6.4 kbp nar gene consisted of narG, H, J, and I in this order. The deduced amino acid sequences of these subunits resembled those of membrane-bound nitrate reductase-A reported for Escherichia coli. It was shown that narG, H, J, and I are transcribed as a single polycistronic message (nar operon). The level of intracellular nar-mRNA was higher when S. ruminantium was grown with nitrate than when grown without nitrate, suggesting that nar transcription is enhanced by nitrate. The level of nar-mRNA, which was in parallel to the amount of NaR per cellular nitrogen, was suggested to be enhanced in response to the deficiency of energy and electron supply. Therefore, NaR synthesis in S. ruminantium appeared to be regulated at the transcriptional level in response to the availability of energy and electrons. S. ruminantium reduced nitrate and fumarate simultaneously with no significant effect of fumarate on nar transcription. Addition of fumarate stimulated nitrate reduction, which was caused by increased cell growth because of increased acquirement of ATP via electron transport phosphorylation coupled with fumarate reduction.

【 授权许可】

Unknown