Fig. 2. Y. pestis YhcN family genes highly induced in the flea gut are involved in an acid stress response. (a) Viability of Y. pestis cells assessed by formazan dye accumulation following a 10 min exposure to pH 4.5 and calculated as the ratio of the A 460 of 1 ml aliquots of cells resuspended in LB pH 4.5 and 7.0, respectively. (b) Relative transcription of the y0666, y1667, y3909 and y3519 genes following exposure of Y. pestis to acidic pH. The RT-qPCR transcript values were normalized to the constitutively expressed crr gene.
