Proteomic analysis of the cold stress response in Campylobacter jejuni

Abstract

Campylobacter jejuni is recognised as one of the most important food-borne pathogens, as it is responsible for causing more cases of gastroenteritis than any other identified bacterial pathogen. Despite the importance of C. jejuni as a human pathogen, little is known about how it copes with different stress factors and survives in the environment. To control the prevalence of food-borne pathogens in food, low temperatures have been widely applied as a practical intervention during food processing and storage. To ensure the cold temperature intervention works optimally, it is important to understand the cold stress response mechanisms employed by C. jejuni. There are a number of integrated genomic/transcriptomic studies that have made progress towards discovering the genes involved in C. jejuni cold tolerance and provided the first step to decodinge the mechanisms employed by C. jejuni to adapt to low temperatures. However, proteomic studies, which reflectthe main components of the physiological metabolic pathways of cells, in C. jejuni’s cold shock and adaptation at refrigeration temperatures, are somewhat lacking. The aim of this study, therefore, was to investigate the cold stress responses of this pathogen using iTRAQ labelling comparative proteomic analysis. Through comparing the alterations in protein expression in three C. jejuni strains during cold shock and cold adaptation, the study found this pathogen dramatically altered its protein expression in response to cold shock. An increased level of ribosomal proteins and other proteins related to protein synthesis in cold-shocked C. Jejuni cells suggested that protein synthesis in C. jejuni was more active when it processed a cold shock response, compared with growing at an optimal temperature. Furthermore, the proteins involved in energy production were present at higher levels in cold-shocked cells. This suggested thatC. Jejuni exhibited an enhanced demand for energy in response to cold shock. The comparative proteomic study also revealed the strategies used by different C. jejuni strains to respond to cold stress. This may provide an explanation for the strain-dependent variability of this pathogen for cold tolerance.