RNA was extracted from strains FA19, CDC2, CR.100, CR.101, CR.102, and CR.104 at mid-logarithmic phase of growth in GC broth plus supplements by the TRIzol method as directed by the manufacturer (Thermo Fisher Scientific, Waltham, MA) and was performed as described previously (59 (link)). Briefly, genomic DNA (gDNA) was removed by RNase-free DNase treatment and gDNA Wipeout (Qiagen, Germantown, MD). The resulting RNA was then reverse transcribed to cDNA using the QuantiTect reverse transcriptase kit (Qiagen) as described previously (57 (link)). Primers 16Smai_qRTF and 16Smai_qRTR were used for 16S rRNA. Primers mtrEqPCR-F and mtrEqPCR-R were used for the mtrE gene, and primers mtrD8 and mtrD13 were used for the mtrD gene. Primers mtrR_qRT_F and mtrR_qRT_R were used for the mtrR gene. Sequences of primers are shown in Table S2. Results were calculated as normalized expression ratios (NERs) using 16S rRNA expression levels. Statistical significance was calculated by Student’s t test.