Protein expression and fatty acid profiles of biofilm cells of chlorhexidinetolerant Delftia acidovorans (MIC = 15 μg/ml) and its chlorhexidine-susceptible mutant (MIC = 1 μg/ml) were investigated. The chlorhexidine-susceptible mutant (MT51) was derived from the parental strain (WT15) using Tn5 transposon mutagenesis. The disrupted gene was identified as tolQ, a component of the tolQRAB gene cluster known to be involved in outer membrane stability. Proteomic responses of biofilm cells were compared by differential in-gel electrophoresis following exposure to chlorhexidine at sub-MIC (10 μg/ml) and above-MIC (30 μg/ml) concentrations. Numerous changes in protein abundance were observed in biofilm cells following chlorhexidine exposure, suggesting that molecular changes occurred during adaptation to chlorhexidine. Forty proteins showing significant differences (≥1.5- fold; P < 0.05) were identified by mass spectrometry and were associated with various functions, including amino acid and lipid biosynthesis, protein translation, energy metabolism, and stress-related functions (e.g., GroEL, aspartyl/ glutamyl-tRNA amidotransferase, elongation factor Tu, Clp protease, and hydroxymyristoyl-ACP dehydratase). Several proteins involved in fatty acid synthesis were affected by chlorhexidine, in agreement with fatty acid analysis, wherein chlorhexidine-induced shifts in the fatty acid profile were observed in the chlorhexidine-tolerant cells, primarily the cyclic fatty acids. Transmission electron microscopy revealed more prominent changes in the cell envelope of chlorhexidine-susceptible MT51 cells. This study suggests that multiple mechanisms involving both the cell envelope (and likely TolQ) and panmetabolic regulation play roles in chlorhexidine tolerance in D. acidovorans.
Bibliographical noteFunding Information:
This work was supported by the Advanced Food and Materials Network (AFMNet), Environment Canada, Health Canada, the Natural Sciences and Engineering Research Council (NSERC) of Canada, and the University of Saskatchewan
© 2016 Rema et al.
- Delftia acidovorans; biofilms; chlorhexidine tolerance; protein expression; tolQ
PubMed: MeSH publication types
- Journal Article