PMID:19307375

Citation	Harrison, JJ, Wade, WD, Akierman, S, Vacchi-Suzzi, C, Stremick, CA, Turner, RJ and Ceri, H (2009) The chromosomal toxin gene yafQ is a determinant of multidrug tolerance for Escherichia coli growing in a biofilm.Antimicrob. Agents Chemother. 53:2253-8
Abstract	Escherichia coli is refractory to elevated doses of antibiotics when it is growing in a biofilm, and this is potentially due to high numbers of multidrug-tolerant persister cells in the surface-adherent population. Previously, the chromosomal toxin-antitoxin loci hipBA and relBE have been linked to the frequency at which persister cells occur in E. coli populations. In the present study, we focused on the dinJ-yafQ-encoded toxin-antitoxin system and hypothesized that deletion of the toxin gene yafQ might influence cell survival in antibiotic-exposed biofilms. By using confocal laser scanning microscopy and viable cell counting, it was determined that a Delta yafQ mutant produced biofilms with a structure and a cell density equivalent to those of the parental strain. In-depth susceptibility testing identified that relative to wild-type E. coli, the Delta yafQ strain had up to a approximately 2,400-fold decrease in cell survival after the biofilms were exposed to bactericidal concentrations of cefazolin or tobramycin. Corresponding to these data, controlled overexpression of yafQ from a high-copy-number plasmid resulted in up to a approximately 10,000-fold increase in the number of biofilm cells surviving exposure to these bactericidal drugs. In contrast, neither the inactivation nor the overexpression of yafQ affected the tolerance of biofilms to doxycycline or rifampin (rifampicin). Furthermore, deletion of yafQ did not affect the tolerance of stationary-phase planktonic cells to any of the antibacterials tested. These results suggest that yafQ mediates the tolerance of E. coli biofilms to multiple but specific antibiotics; moreover, our data imply that this cellular pathway for persistence is likely different from that of multidrug-tolerant cells in stationary-phase planktonic cell cultures.
Links	PubMed Online version:10.1128/AAC.00043-09
Keywords	Bacterial Toxins; Biofilms; Drug Resistance, Multiple, Bacterial; Escherichia coli; Escherichia coli Proteins; Planktonic Cells
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Materials and Methods Used

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Phenotype Annotations

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Species	Taxon ID	Strain	Gene (if known)	OMP	Phenotype	Details	Evidence	Notes
Escherichia coli		JW0215	del yafQ	decreased cell survival in biofilm increased susceptibility to antibiotics decreased biofilm tolerance to antibiotics	Growth	CFU count vs. antibiotic concentration- cefazolin or tobramycin	Plating Assay	Figure 2
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