F factor inhibition of conjugal transfer of broad-host-range plasmid RP4: requirement for the protein product of pif operon regulatory gene pifC

Abstract

By the use of deletions, point mutations, and gene fusions, we show that the protein product of the F factor pijC gene is responsible for F factor inhibition of plasmid RP4 conjugal transfer. Deletion analysis of pif sequences carried by pSC101-F chimeric plasmids demonstrated that removal of all or part of the pifC coding sequence greatly decreased or abolished the ability of these plasmids to inhibit RP4 transfer. Amber mutations in the pifC gene eliminated inhibition in an Suhost strain but not in and Su' (supF) host. Plasmids carrying nonpolar pifC mutations did not decrease the efficiency of RP4 transfer when present in trans. Whereas pifC+ plasmids inhibited RP4 transfer, the presence of RP4 in the same cell as F' lac increased F'lac Pif activity * Corresponding author. genotype JF50 F-Alac(X74) supFS8 Nalr J. Felton JF270 F-Alac(X74) recA rpsL J. Felton RV101 F-Alac(X74) gyrA01 Derived from strain RV (17) RV200 F-Alac(X74) rpsL200 Derived from strain RV (17) W3110::Tn7 F-Tn7 (Tpr) P. T. Barth

Both the fipA Gene of pKM101 and the pifC Gene of F Inhibit Conjugal Transfer of RP1 by an Effect on traG

“…We characterize the gene in pKM101, here named fipA, and show that both fipA and pifC exert their inhibition effects via traG. We also present evidence that the interaction between pifC and traG occurs at the protein level and not, as previously suggested (43), by binding to RP1 DNA.…”

“…Characteristics of fipA and pifC and the ability of these genes to inhibit RP1-mediated mobilization of nonconjugative plasmids. The pifC gene of plasmid F, like fipA (76), inhibits the conjugal transfer of RP1 without affecting surface exclusion (Sfx ϩ ) or sensitivity to donor-specific phages (Dps ϩ ) (43,68). Inhibition by pifC is, however, at least 100-fold weaker than that by fipA.…”

“…To investigate this further, we took advantage of the role of PifC to negatively regulate the F pif operon, the expression of which inhibits the propagation of phage T7 (denoted Pif ϩ ) (31, 56). Miller et al (43) showed that FЈlac Pif activity increased in cells that also carried RP4 (ϭRP1), reflecting the removal of PifC with consequent reduced plating and altered plaque morphology (denoted Pif ϩϩ ). The Pif phenotype thus provides an in vivo assay of the levels of PifC, and we used this phenotype to further study pifC-mediated inhibition of traG.…”

Plasmid transfer is biased towards close kin in bacteria from natural populations

“…Similar results were obtained with phages, where MG1655 was found to be susceptible to many more phages than natural E. coli isolates (Allen et al, 2016). Interactions between plasmids and other elements like prophages might also affect transfer operon expression (Miller et al, 1985) or plasmid cost (San Millan et al, 2015) and explain why donor ability is lower than in K-12 for the majority of field isolates, that probably bear an abundance of prophages and other mobile elements.…”

Ecological and genetic determinants of plasmid distribution in Escherichia coli

“…While some of these associations may arise because large IncF –type plasmids will often carry both IncF1A and F1B replicons (Villa et al ., ), the association between IncF1B and IncP replicons was novel. Conversely, antagonistic interactions between IncF1A and IncP, which are known to interfere in other's conjugation potential (Miller et al ., ) may explain the rare co‐occurrence of these two replicon types.…”