Comparison of transcript ranks for genes involved in stress responses and quorum sensing. Shown are comparisons for selected genes involved in oxidative stress (A); copper stress (B); efflux pumps (C); and homoserine lactone quorum sensing (D). Symbols correspond to individual data sets as given in Table 2 and Additional file 1. An asterisk next to a data point indicates a statistically significant difference between the indicated data set and the combined data of three standard comparator data sets (see Materials and Methods for specifics). Where a label such as "Cu stress" appears, it denotes a transcriptome that can be considered a positive control. Where no such label appears, a suitable positive control data set was lacking.