Environmental Microbiology, December 2016, Vol.18(12), pp.5277-5287
Plasmids of the incompatibility group HI1 (IncHI1) have been isolated from several Gram‐negative pathogens and are associated with the spread of multidrug resistance. Their conjugation is tightly regulated and it is inhibited at temperatures higher than 30°C, indicating that conjugation occurs outside warm‐blooded hosts. Using R27, the prototype of IncHI1 plasmids, we report that plasmid transfer efficiency in strongly depends on the physiological state of the donor cells. Conjugation frequency is high when cells are actively growing, dropping sharply when cells enter the stationary phase of growth. Accordingly, our transcriptomic assays show significant downregulation of numerous R27 genes during the stationary phase, including several (transfer) genes. Growth phase‐dependent regulation of genes transcription is independent of H‐NS, a silencer of horizontal gene transfer, and ppGpp and RpoS, regulators of the stationary phase, but highly dependent on the plasmid‐encoded regulatory circuit TrhR/TrhY‐HtdA. The metabolic sensor cAMP, whose synthesis is chromosomally encoded, is also involved in the growth phase regulation of R27 conjugation by modulating expression. Our data suggest that the involvement of regulators encoded by both chromosome and plasmid are required for efficient physiological control of IncHI1 plasmid conjugation.
Cyclic Adenosine Monophosphate – Physiological Aspects ; Cyclic Adenosine Monophosphate – Growth ; Genetic Research – Physiological Aspects ; Genetic Research – Growth ; Genes – Physiological Aspects ; Genes – Growth ; Sensors – Physiological Aspects ; Microbial Drug Resistance – Physiological Aspects ; Microbial Drug Resistance – Growth;