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Archaea
Volume 1 (2002), Issue 2, Pages 143-150
http://dx.doi.org/10.1155/2002/362813
Research Article

Functional organization of a single nif cluster in the mesophilic archaeon Methanosarcina mazei strain Gö1

1Abteilung Allgemeine Mikrobiologie, Institut für Mikrobiologie und Genetik der Georg-August-Universität, Grisebachstr. 8, 37077 Göttingen, Germany
2Göttingen Genomics Laboratory, Institut für Mikrobiologie und Genetik der Georg-August-Universität, Grisebachstr. 8, 37077 Göttingen, Germany

Received 6 June 2002; Accepted 10 July 2002

Copyright © 2002 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The mesophilic methanogenic archaeon Methanosarcina mazei strain Gö1 is able to utilize molecular nitrogen (N2) as its sole nitrogen source. We have identified and characterized a single nitrogen fixation (nif) gene cluster in M. mazei Gö1 with an approximate length of 9 kbp. Sequence analysis revealed seven genes with sequence similarities to nifH, nifI1, nifI2, nifD, nifK, nifE and nifN, similar to other diazotrophic methanogens and certain bacteria such as Clostridium acetobutylicum, with the two glnB-like genes (nifI1 and nifI2) located between nifH and nifD. Phylogenetic analysis of deduced amino acid sequences for the nitrogenase structural genes of M. mazei Gö1 showed that they are most closely related to Methanosarcina barkeri nif2 genes, and also closely resemble those for the corresponding nif products of the gram-positive bacterium C. acetobutylicum. Northern blot analysis and reverse transcription PCR analysis demonstrated that the M. mazei nif genes constitute an operon transcribed only under nitrogen starvation as a single 8 kb transcript. Sequence analysis revealed a palindromic sequence at the transcriptional start site in front of the M. mazei nifH gene, which may have a function in transcriptional regulation of the nif operon.