Expression Analysis of Genes in the Nif Cluster of Clostridium beijerinckii

摘要

The nif genes of Clostridium beijerinckii NRRL B593 occupy a region of about 16 kilobases. Besides the two glnB-like genes, five other genes are interspersed between the nifNB and the nifVw genes. An expression analysis of the nif genes in nitrogen-fixing and non-nitrogen-fixing cells with probes generated from various regions of the nif cluster by northern blot analysis revealed the presence of four different transcripts in nitrogen-fixing cells. Two of these transcripts had the predicted sizes spanning from nifH to nifK and from nifVw to nifVa, respectively. The other two transcripts did not have the expected sizes, but they suggested the presence of two other polycistronic mRNAs consisting of nifE-nifNB and nirJ1-nirJ2-nirD-nirH, respectively. The absence of the nif and nif-associated mRNAs in RNA samples from non-nitrogen-fixing cells indicated that nif-associated genes are regulated in parallel to nif genes.