Abstract
To study the function of the major periplasmic domain of the inner membrane insertase YidC, Choi et al. (JEMI, Volume 20) constructed two chromosomal yidC knockout strains of Escherichia coli, WJKC-1 and WJKC-2. WJKC-1 strain contains pEH1-yidC-GFP plasmid, which encodes the entire yidC gene. WJKC-2 strain contains the pYidC-Δp1-GFP-Xu plasmid, which lacks the major periplasmic domain of YidC. Preliminary growth experiments suggested a temperature sensitive phenotype as these strains grew at 20°C and 30°C but not at 37°C. Here we investigate the location of the chloramphenicol (camR) cassette by polymerase chain reaction. The PCR experiments demonstrated proper primer binding to the positive controls, but only nonspecific binding to WJKC-1 and WJKC-2 genomic DNA. The sequencing results obtained from the junction between camR cassette and the neighboring gene, mnmE, lead us to investigate the possibility of Rhizobium species. 16 SSU rRNA amplification and sequencing confirmed that WJKC-1 and WJKC-2 are indeed Rhizobium species.