"Take It or Leave It"-Factors Regulating Competence Development and DNA Uptake in Campylobacter jejuni.

Julia C Golz,Kerstin Stingl

doi:10.3390/ijms221810169

Julia C Golz, Kerstin Stingl

Open Access

https://doi.org/10.3390/ijms221810169

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Abstract

Campylobacter jejuni has a large adaptive potential due to enormous genetic exchange. Factors regulating natural transformation in this food-borne pathogen are largely unknown but of interest for the application of sustained reduction strategies in the food-processing industry. Using a single cell DNA uptake assay, we visualized that recognition of methylated C. jejuni DNA was essential for the first step of DNA uptake into a DNase resistant state. Transformation rates using a resistance marker correlated with the fraction of competent bacteria, harboring one to maximally four locations of active DNA uptake, not necessarily being located at the cell pole. Competence developed with rising pH between 6.5 and 7.5 under microaerobic conditions and was nearly insensitive towards growth temperatures between 32 °C and 42 °C, CO2 concentrations ranging from 0 to 50% and growth rates. However, competence development was abolished at pH 5 or under aerobic stress conditions, in which the bacteria ceased growth but fully survived. The DNA uptake machinery in competent bacteria shut down at slightly acidic pH and was reversibly switched on upon neutralization. It was dependent on the proton motive force and, in contrast to competence development, slightly enhanced under aerobic conditions. The results suggest that natural transformation in C. jejuni occurs in the neutral and microaerobic intestinal environment for enhanced genetic diversity and pre-adaption before host switch. In addition, highly competent bacteria might be shed into the environment, still able to acquire genetic material for increased survival.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
In contrast to H. pylori, C. jejuni DNA uptake is limited to DNA substrates, which harbor RATTY sites methylated by Campylobacter spp. specific CtsM methylase [26]
In order to establish the single cell assay for C. jejuni, genomic DNA extracted from C. jejuni served as DNA substrate, rather than DNA of the E. coli bacteriophage λ, previously used for H. pylori

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Campylobacter jejuni is a human foodborne pathogen causing the majority of bacterially induced gastroenteritis in the European Union, with 220,682 reported cases in 2019 [1]. The pathogen resides in birds, and pigs, cattle and other animals are frequently colonized by the bacterium [2,3,4]. C. jejuni infection of humans primarily occurs via contaminated food, in particular due to cross-contamination from raw poultry meat to ready-to-eat fresh food and by consumption of undercooked poultry, other raw meat and milk [5,6]

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