Mobile elements carrying ermF and tetQ genes in Gram-positive and Gram-negative bacteria

Bacteroides spp. conjugative transposon Tn5030 is 150 kb which includes a 43 kb characterized region containing a number of defined genes and an open reading frame (ORF). The 43 kb region is organized with the ORF1 immediately upstream from the ermF gene, coding for an rRNA methylase, then an unknown 20 kb region downstream followed by the tetQ gene (coding for a ribosomal protection protein) then the rteA and rteB genes. The role of ORF1 is unclear; rteA is a putative sensor and rteB a regulator. Thirty-seven (62%) of 60 isolates, representing one Gram-positive anaerobic and 13 Gram-negative anaerobic species, co-transferred the ermF and tetQ genes to an unrelated Enterococcus faecalis recipient. We used the polymerase chain reaction to show the linkage between ORF1, ermF, tetQ, rteA and rteB. Our data suggest that the ORF1 gene product may participate in the transfer of the ermF gene with or without the ORF1-rteB region and has homology to bacterial transposases. Isolates that co-transferred the ermF and tetQ genes carried and transferred the rteB gene, suggesting that the rteB gene product may be important in transfer of the 43 kb ORF1-rteB region to E. faecalis. The rfeB gene product is not required when ermF is transferred independently of tetQ.