C. jejuni CsrA is divergent from the E. coli ortholog, including in the RNA binding domains. A) CsrA orthologs from 20 diverse pathogenic and non-pathogenic bacterial species were aligned using CLUSTALW (neighbor joining). Numbers at tree nodes indicate the percent of bootstrap replicates that support the adjacent branches. Protein lengths (number of amino acids) are indicated to the right of each ortholog. Accession numbers for each protein are listed in Additional file 1: Table S1. B) Alignment of the amino acid sequences of CsrA orthologs. Regions 1 and 2 of E. coli CsrA important for RNA binding  are indicated by boxes and other amino acid residues important for CsrA regulation are indicated by an asterisk (*). Red shading indicates amino acids that are identical to those of E. coli CsrA; purple shading indicates amino acids that are different from E. coli CsrA but identical within the C. jejuni-containing clade of Figure 1A. Amino acids within RNA binding sequences 1 and 2 of C. jejuni CsrA that are conservative substitutions compared to E. coli CsrA are underlined.