EcoRI restriction endonuclease map of the composite R plasmid NR1

Abstract

A physical map of the composite R plasmid NR1 has been constructed using specific cleavage of deoxyribonucleic acid (DNA) by the restriction endonuclease EcoRI. Digestion of composite NR1 DNA by EcoRI yields thirteen fragments. The six largest fragments (designated A to F) are from the resistance transfer factor component that harbors the tetracycline resistance genes (RTF-TC). The seven smallest fragments (designated G to M) are from the r-determinants component that harbors the chloramphenicol (CM), streptomycin-spectinomycin (SM/SP), and sulfonamide (SA) resistance genes. The largest fragment of several RTF-TC segregants of NR1 that have deleted the r-determinants component is 0.8 x 106 daltons larger than fragment A of composite NR1. Only a part of fragment H of the r-determinants component is amplified in transitioned NR1 DNA in Proteus mirabilis, which consists of multiple, tandem sequences of rdeterminants attached to a single copy of the RTF-TC component. Both of these changes can be explained by the locations of the excision sites at the RTF-TC: rdeterminants junctions that are involved in the dissociation and reassociation of the RTF-TC and r-determinants components. The thirteen fragments of composite NR1 DNA produced by EcoRI have been ordered using partial digestion techniques. The order of the fragments is:rA-D-C-E-F-B-H-I-L-K-G-M-J1.The approximate locations of the TC, CM, SM/SP, and SA resistance genes on the EcoRI map were determined by analyzing several deletion mutants of NR1.

Recombination between two IS/s flanking the r-determinant of R100-1: involvement of dor and recA gene functions in Salmonella typhimurium

“…1 (lanes bl through b3). Both the R100-1 fragments A and H hybridized with ISI-specific DNA, and the result is consistent with those of Rownd et al (21,26) and Chandler et al (4). IS)specific DNA was also found in fragment A' of R100-11 (Fig.…”

“…From the above results, R100-11 without the entire r-det was considered to be identical to an RTF plasmid described by Tanaka et al (26) and an RTF-Tc plasmid described by Chandler et al (4). These suggested that R100-11 may be a b 81 a2 83 84 a5 bi b2 b3 b4 b5 ES formed by a reciprocal recombination between two ISls (which exist in fragment A and H) flanking the r-det and by the subsequent loss of the r-det.…”

“…DNA of R100-1 and its derivatives did not hybridize with 32P-labeled A cI-71 without the IS) sequences (data not shown). c, Summarized EcoRI restriction endonuclease map of R100-1 and the location of the resistance genes based on published data (14,20,26). VOL.…”

Effects of nutrient-poor and anaerobic conditions on maintenance of R100-1 and RSF2124 plasmids in model populations of Escherichia coli.

“…The nalidixic acid resistant mutant of HB 101 was obtained by N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis and designated HB101N. R100-1 is the permanently derepressed transfer mutant of R100 which carries resistance genes to several antibiotics and mercuric ion (Tanaka et al, 1976). RSF2124 is a non-selftransmissible, mobilizable plasmid (So et al, 1975).…”

Deletion Mutants from R Plasmids with Increased Copy Number

“…R100 and Rms 201 seem to possess analogous genes in a similar order on an R genome. The replication gene on the ampminiplasmids or on Rms 201 would be analogous to repA in R100 whose location is near the cop gene and is between tra and the (sul str cml) cluster (17)(18)(19).…”