Expression of genes encoding sigma factors under conditions of simulated stresses. The fold-change value was based on the ratio between the stress RPKM and the control RPKM. Green columns indicate the differentially expressed genes, independent of the fold-change cutoff established for the analysis, which was at least 2x. Red columns represent the genes not differentially expressed (p-value >0.001), established using the DEGseq programme. a, Osmotic stress. b, Acid stress. c, Thermal stress.