Comparison of phylogenetic trees based on complete sequences of luxS (A), lsrB (B) and rpoB (C). All trees are restricted to strains which are both luxS- and lsrB-positve. The distance tree was generated by the NJ method with the JC formula, without choosing any outgroup. Nodal supports were assessed by 1000 bootstrap replicates. Only bootstrap values greater than 50% are shown. The scale bar represents the number of substitutions per site. All sequences were retrieved at the NCBI database or in published genome projects (see Methods for accession numbers).