TY - JOUR
T1 - Isolation of the replication and partitioning regions of the Salmonella typhimurium virulence plasmid and stabilization of heterologous replicons
AU - Tinge, S. A.
AU - Curtiss, R.
PY - 1990
Y1 - 1990
N2 - Although the virulence plasmid of Salmonella typhimurium has a copy number of one to two per chromosome, plasmid-free segregants are produced at a rate less than 10-7 per cell per generation. Three regions appear to be involved in the maintenance of this virulence plasmid. The first two, repB and repC, are functional replicons hybridizing with IncFII and IncFI plasmids, respectively, neither exhibiting the segregational stability of the parent virulence plasmid. The third region, par, cloned as a 3.9-kilobase Sau3A fragment, is not a functional replicon but exhibits incompatibility with the virulence plasmid. Subsequent tests revealed the ability of this 3.9-kilobase par insert to increase the stability of pACYC184 in S. typhimurium from less than 34% to 99% plasmid-containing cells after 50 generations. In addition, the par region increased the stability of oriC, R388, and repC replicons in both S. typhimurium and Escherichia coli hosts. The par region encodes 44,000- and 40,000-molecular-weight proteins essential for the Par+ phenotype but not for the Inc+ phenotype. Although actual sequestering of plasmids within the cell was not demonstrated, all results indicate that the par region described is an actual partitioning locus, similar in organization to those described for plasmids F, P1, and NR1.
AB - Although the virulence plasmid of Salmonella typhimurium has a copy number of one to two per chromosome, plasmid-free segregants are produced at a rate less than 10-7 per cell per generation. Three regions appear to be involved in the maintenance of this virulence plasmid. The first two, repB and repC, are functional replicons hybridizing with IncFII and IncFI plasmids, respectively, neither exhibiting the segregational stability of the parent virulence plasmid. The third region, par, cloned as a 3.9-kilobase Sau3A fragment, is not a functional replicon but exhibits incompatibility with the virulence plasmid. Subsequent tests revealed the ability of this 3.9-kilobase par insert to increase the stability of pACYC184 in S. typhimurium from less than 34% to 99% plasmid-containing cells after 50 generations. In addition, the par region increased the stability of oriC, R388, and repC replicons in both S. typhimurium and Escherichia coli hosts. The par region encodes 44,000- and 40,000-molecular-weight proteins essential for the Par+ phenotype but not for the Inc+ phenotype. Although actual sequestering of plasmids within the cell was not demonstrated, all results indicate that the par region described is an actual partitioning locus, similar in organization to those described for plasmids F, P1, and NR1.
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U2 - 10.1128/jb.172.9.5266-5277.1990
DO - 10.1128/jb.172.9.5266-5277.1990
M3 - Article
C2 - 2203747
AN - SCOPUS:0025079158
SN - 0021-9193
VL - 172
SP - 5266
EP - 5277
JO - Journal of bacteriology
JF - Journal of bacteriology
IS - 9
ER -