Expression of selected genes in the ΔSMcomS strain in response to increasing concentrations of XIP. RT-PCR analysis of gene expression was performed in ΔSMcomS grown in CDM to an OD600 of 0.4 in the presence of increasing amounts of XIP. *, P < 0.05; **, P < 0.005. Expression of selected genes in the ΔSMcomS strain in response to increasing concentrations of XIP. RT-PCR analysis of gene expression was performed in ΔSMcomS grown in CDM to an OD600 of 0.4 in the presence of increasing amounts of XIP. *, P < 0.05; **, P < 0.005. Iwona B. Wenderska et al. mSystems 2017; doi:10.1128/mSystems.00102-16