Genome-Wide Screen for Escherichia coli Genes Involved in Repressing Cell-To-Cell Transfer of a Nonconjugative pSC101-Derived Plasmid

Abstract

Acquiring new genetic traits by lateral gene transfer is a bacterial strategy for environmental adaptations. We previously showed that Escherichia coli laterally transmits nonconjugative plasmids in cocultures that contain strains with or without the plasmid. Using a pMB1-derived plasmid and the Keio collection, a comprehensive library of E. coli knockout mutants for nonessential genes, we recently screened for genes responsible for promoting or repressing cell-to-cell plasmid transfer in recipient cells. In this study, we used a pSC101-derived plasmid, instead of a pMB1-derived plasmid, to screen for repressing genes and identified 29 "transfer-up" mutants. Among these, four mutants are common to those previously screened using a pMB1-derived plasmid. Although the roles of the 29 gene products in plasmid transfer mechanism remain uncertain, it is interesting that 28 of the 29 screened genes map to two limited regions on the E. coli chromosome: 18 genes at 34.25-35.31 min and 10 genes at 12.62-13.35 min. Because these two regions commonly contain termination (Ter) sites for DNA replication (TerC: 34.64 min and TerH: 12.91 min), it is possible that chromosomal mutations around specific Ter sites may affect plasmid acquisition in the recipient cells.

Bacteriophage P1<em>vir</em>-induced cell-to-cell plasmid transformation in <em>Escherichia coli</em>

“…In addition, we previously demonstrated that CAG18439 shows no promoting effect on simple natural transformation with purified plasmids [15]. These features indicate the novelty and uniqueness of this transformation mechanism, as suggested previously [15]–[19]. We speculate that a certain P1-phage protein or E. coli protein, whose size was estimated to be between 9 and 15 kDa [15], induced by P1 infection also helps with this transformation in an unknown manner that differs from that in transduction.…”

“…We termed this transformation “cell-to-cell transformation” [15]. Subsequent studies of genome-wide screens for the genes involved in DNA acquisition in recipient cells have suggested that this plasmid transfer does not involve simple transformation but is instead a complicated phenomenon [17],[18],[19].…”

Horizontal Plasmid Transfer by Transformation in Escherichia coli: Environmental Factors and Possible Mechanisms

“…This factor presumably assists in DNA uptake by recipient cells, probably in combination with the 88-bp sequence on the transforming DNA. Lastly, with respect to (4), later genome-wide screening studies for recipient genes involved in HPTT suggested that multiple genes participate in the mechanism ( Kurono et al, 2012 ; Matsuda et al, 2012 ; Shibata et al, 2014a ). These include those that have not been reported to be involved in natural or artificial transformation in E. coli (such as rodZ ) and a few known competence gene homologs, such as ybaV and yhiR ( Finkel and Kolter, 2001 ; Palchevskiy and Finkel, 2006 ), but do not include rpoS and other genes related to the RpoS-dependent mechanism ( Zhang et al, 2012 ).…”