Table 1 Phenotypes caused by altering the XreR1 or XreR2 number in P. luminescens 1° and 2° cells. The P. luminescens strains 2° ΔxreR2, 2° + PconstxreR1 and 1°ΔxreR1 + PconstxreR1 exhibited the 1° phenotype while the P. luminescens strains 1° ΔxreR1, 1° + PconstxreR2 and 2° ΔxreR2 + PconstxreR2 showed the 2° phenotype