Proteome Profiling by Label‐Free Mass Spectrometry Reveals Differentiated Response of Campylobacter jejuni 81–176 to Sublethal Concentrations of Bile Acids

Abstract

Purpose Bile acids are crucial components of the intestinal antimicrobial defense and represent a significant stress factor for enteric pathogens. Adaptation processes of Campylobacter jejuni to this hostile environment are analyzed in this study by a proteomic approach. Experimental design Proteome profiling by label‐free mass spectrometry (SWATH‐MS) has been used to characterize the adaptation of C. jejuni to sublethal concentrations of seven bile acids. Results The bile acids with the lowest inhibitory concentration (IC50), deoxycholic and chenodeoxycholic acid, induce the most significant proteome changes. Overall a downregulation of all basic biosynthetic pathways and a general decrease in the transcription machinery are found. Concurrently, an induction of factors involved in detoxification of reactive oxygen species, protein folding, and bile acid exporting efflux pumps is detected. Exposure to deoxycholic and chenodeoxycholic acid results in an increased expression of components of the more energy‐efficient aerobic respiration pathway, while the anaerobic branches of the electron transport chain are down‐expressed. Conclusions and clinical relevance The results show that C. jejuni has a differentiated system of adaptation to bile acid stresses. The findings enhance the understanding of the pathogenesis of campylobacteriosis, especially for survival of C. jejuni in the human intestine, and may provide clues to future medical treatment.

Genome and Methylome analysis of a phylogenetic novel Campylobacter coli cluster with C. jejuni introgression

“…CmeABC and CmeDEF are involved in bile resistance [ 35 ]. Bile acids, especially deoxycholic acid, chenodeoxy-cholic acid and glycocholic acid, have been demonstrated to induce the expression of cmeA , cmeB , cmeC and cmeE [ 36 ]. The uptake of these genes from C. jejuni might be an adaptation to an intestinal bile acid-containing habitat.…”

Bacterial succession and specialization within the poultry gastrointestinal tract

“…7α/β-dehydroxylation can also serve as an electronaccepting reaction for these bacteria, producing an NADPH molecule (101,173). Both DCA and LCA act as chemical signals for certain bacteria, leading to the upregulation of genes involved in colonization and growth, as well as triggering biofilm formation and leading to conformational changes to promote gut colonization and persistence (258)(259)(260)(261)(262)(263)(264). While 7α/β-dehydroxylation may be beneficial for some bacterial species, the minimum inhibitory concentration range for LCA and DCA is much lower than for conjugated and unconjugated primary BAs, likely due to the increased hydrophobicity, allowing for a more rapid transit of the secondary BA into the cell and the induction of similar stressors to bacteria (147,150,173,265).…”

Characterization of genes differentially regulated after bile acid exposure in Campylobacter jejuni

“…Novel pathogenicity factors involved in the ability of C. jejuni to adapt to the bile acid rich environment of the human gut are aimed to be identified by the generation of knockout mutants. Candidate genes were mainly chosen from proteomics data generated on the previous study from Masanta (2018) that resulted in the identification of differentially expressed proteins after exposure to sublethal concentrations of bile acids.…”

“…We used three criteria to select the target genes: (i) the corresponding protein is regulated by bile acid exposure with a focus on downregulated proteins (Masanta et al 2018), (ii) the regulation occurs preferentially in response to Deoxycholic acid (DCA) and/or Chenodeoxycholic acid (CDCA), and (iii) target genes should belong to multiple functional groups, e.g. transporter, surface proteins, signaling factors, enzymes, etc.…”

“…Based on the previous study from Masanta (2018) and de Vries (2017) we selected potential genes to generate knockout mutants. Our main focus was on genes that presented corresponding proteins differentially regulated after sublethal concentrations of bile acid exposure.…”