Acid stress response and protein induction in Campylobacter jejuni isolates with different acid tolerance

Tina Birk,Monica Takamiya Wik,Susanne Knøchel,René Lametsch

doi:10.1186/1471-2180-12-174

Tina Birk, Monica Takamiya Wik + Show 2 more

Open Access

https://doi.org/10.1186/1471-2180-12-174

Copy DOI

Abstract

BackgroundDuring the transmission route from poultry to the human host, the major foodborne pathogen C. jejuni may experience many types of stresses, including low pH caused by different acids. However, not all strains are equally sensitive to the stresses. The aim of this study was to investigate the response to acid stress of three sequenced C. jejuni strains with different acid tolerances using HCl and acetic acid.ResultsTwo-dimensional gel electrophoresis was used for proteomic analysis and proteins were radioactively labelled with methionine to identify proteins only related to acid exposure. To allow added radioactive methionine to be incorporated into induced proteins, a modified chemically defined broth was developed with the minimal amount of methionine necessary for satisfactory growth of all strains. Protein spots were analyzed using image software and identification was done with MALDI-TOF-TOF. The most acid-sensitive isolate was C. jejuni 327, followed by NCTC 11168 and isolate 305 as the most tolerant. Overall, induction of five proteins was observed within the pI range investigated: 19 kDa periplasmic protein (p19), thioredoxin-disulfide (TrxB), a hypothetical protein Cj0706 (Cj0706), molybdenum cofactor biosynthesis protein (MogA), and bacterioferritin (Dps). Strain and acid type dependent differences in the level of response were observed. For strain NCTC 11168, the induced proteins and the regulator fur were analysed at the transcriptomic level using qRT-PCR. In this transcriptomic analysis, only up-regulation of trxB and p19 was observed.ConclusionsA defined medium that supports the growth of a range of Campylobacter strains and suitable for proteomic analysis was developed. Mainly proteins normally involved in iron control and oxidative stress defence were induced during acid stress of C. jejuni. Both strain and acid type affected sensitivity and response.

Highlights

During the transmission route from poultry to the human host, the major foodborne pathogen C. jejuni may experience many types of stresses, including low pH caused by different acids
In order to minimize the competition between the methionine and the radioactive methionine in the modified chemically defined broth (CDB), the minimal concentration of methionine in the modified CDB was determined for the three strains
The modified CDB with 0.01 mM methionine was used in 2D gel analysis because no significant difference in growth was observed between this concentration and the highest concentration (0.1 mM) investigated (P305 = 0.07, P11168 = 0.36, P327 = 0.52) (Figure 1)

Summary

Introduction

During the transmission route from poultry to the human host, the major foodborne pathogen C. jejuni may experience many types of stresses, including low pH caused by different acids. Compared with many other foodborne pathogens, C. jejuni is more sensitive towards stress such as acid [1,2,3] and has stringent requirements for optimal growth conditions [4]. C. jejuni is more sensitive to stress and has a limited number of stress regulators. C. jejuni lacks the global stationary-phase regulator, sigma factor RpoS, which induces expression of numerous proteins involved in different forms of stress responses [14] and it is involved in acid stress in E. coli and Salmonella [15,16]. Compared with many other foodborne pathogens, C. jejuni is more sensitive to acid exposure [23]. How does C. jejuni respond on the proteomic level when exposed to low pH?

Objectives

Methods

Results

Discussion

Conclusion