Figure 2

Identification of an expression island in the A1501 genome that supports nitrogen fixation. (A) Schematic representation of the regions in the A1501 chromosome with upregulated and downregulated gene expression. Upregulated (red lines) and downregulated (blue lines) genes under nitrogen fixation and ammonium shock conditions. The 49-kb nif gene expression island (red bar) is located in the chromosome (from PST1302 to PST1359). (B) Predicted operons (black arrows) with conserved RpoN and NifA promoters. The open and filled boxes represent the putative σ⁵⁴-dependent promoter and upstream activator sequences, respectively.