Quorum Sensing N-acyl Homoserine Lactones-SdiA Suppresses Escherichia coli-Pseudomonas aeruginosa Conjugation through Inhibiting traI Expression

Abstract

Conjugation is a key mechanism for horizontal gene transfer and plays an important role in bacterial evolution, especially with respect to antibiotic resistance. However, little is known about the role of donor and recipient cells in regulation of conjugation. Here, using an Escherichia coli (SM10λπ)-Pseudomonas aeruginosa (PAO1) conjugation model, we demonstrated that deficiency of lasI/rhlI, genes associated with generation of the quorum sensing signals N-acyl homoserine lactones (AHLs) in PAO1, or deletion of the AHLs receptor SdiA in the donor SM10λπ both facilitated conjugation. When using another AHLs-non-producing E. coli strain EC600 as recipient cells, deficiency of sdiA in donor SM10λπ hardly affect the conjugation. More importantly, in the presence of exogenous AHLs, the conjugation efficiency between SM10λπ and EC600 was dramatically decreased, while deficiency of sdiA in SM10λπ attenuated AHLs-inhibited conjugation. These data suggest the conjugation suppression function of AHLs-SdiA chemical signaling. Further bioinformatics analysis, β-galactosidase reporter system and electrophoretic mobility shift assays characterized the binding site of SdiA on the promoter region of traI gene. Furthermore, deletion of lasI/rhlI or sdiA promoted traI mRNA expression in SM10λπ and PAO1 co-culture system, which was abrogated by AHLs. Collectively, our results provide new insight into an important contribution of quorum sensing system AHLs-SdiA to the networks that regulate conjugation.

Discovery of a Novel Dibromoquinoline Compound Exhibiting Potent Antifungal and Antivirulence Activity That Targets Metal Ion Homeostasis

“…Hence, the targeted activity and corresponding deletion strains have increased growth sensitivity compared to a genome-wide set of deletion strains. We have previously applied chemogenomic profiling to identify biological pathways targeted by an FDA-approved drug, auranofin, and a molecule in clinical trials, ebselen, which were found to possess antifungal activity 37, 38 . Utilizing this approach, 34 heterozygous diploid deletion strains were sensitive to 4b (Supplementary Table 1).…”

“…Given 4b ’s promising antifungal activity in vitro , combined with its potent antivirulence activity against C. albicans hyphae and biofilm formation, it was critical to evaluate whether the compound’s activity could be retained in vivo. C. elegans is an excellent animal model for early-stage evaluation of promising anti-infective and antivirulence agents prior to evaluating agents in mammalian models such as rodents 38, 43–46 . A challenge of translating antifungal compounds to clinical applications are issues pertaining to toxicity and rapid metabolism.…”

“…4b (55 μM; 30μg/mL) delayed growth of BY4743 by 30% compared to the no drug control half-maximal optical density (OD). Chemogenomic haploinsufficiency profiling using the complete genome-wide heterozygous deletion strain pool (Thermo Fisher Scientific, Waltham, MA) was performed as previously described 38 . A frozen aliquot (200 μL) of the pool was thawed and inoculated into 2 mL of YPD and grown for nine hours until OD 600 of 4.0.…”

“…The reads for each experiment were identified using a 5 base multiplex tag and subsequent unique barcodes in each experimental sample was cross-referenced to a database of recharacterized barcode sequences 54 . The resulting strain counts were analyzed with edgeR 55 using previously described parameters 38 .…”

“…An overnight suspension of S. cerevisiae strains were diluted (OD 600 ~ 0.05) and grown in the presence of 4b (7.5 μg/mL). Growth for the wild-type ( S. cerevisiae BY4743) and mutant strains was monitored using a spectrophotometer (OD 600 ) at indicated time points for 20 hours, as described elsewhere 38 .…”