The transcriptional response of Arcobacter butzleri to cold shock

Abstract

Arcobacter (A.) butzleri is an emerging zoonotic pathogen associated with gastrointestinal diseases, such as abdominal cramps and diarrhea, and is widely detected in animals, showing a high prevalence in poultry and seafood. The survival and adaptation of A. butzleri to cold temperatures remains poorly studied, although it might be of interest for food safety considerations. To address this, growth patterns of eight A. butzleri isolates were determined at 8°C for 28 days. A. butzleri isolates showed strain-dependent behavior: six isolates were unculturable after day 18, one exhibited declining but detectable cell counts until day 28 and one grew to the stationary phase level. Out of 13 A. butzleri cold shock-related genes homologous to Escherichia coli, 10 were up-regulated in response to a temperature downshift to 8°C, as demonstrated by reverse transcription-quantitative PCR. Additionally, we compared these data with the cold-shock response in E. coli. Overall, we provide a deeper insight into the environmental adaptation capacities of A. butzleri, which we find shares similarities with the E. coli cold-shock response. Arcobacter spp. is an emerging zoonotic pathogen associated with gastrointestinal diseases such as abdominal cramps and diarrhea [1-3]. Among the 29 species within the genus of Arcobacter described so far [4], A. butzleri is the most widely detected species in animals, environment and foods, with high prevalences in poultry meat and seafood samples [5-10]. Although the good environmental adaptability of A. butzleri is well known, the survival and adaptation of A. butzleri to cold remains poorly studied so far, although it might be of interest for food safety considerations. A. butzleri has an optimal growth temperature of 30°C under both aerobic and microaerobic conditions but is likely to be exposed to a wide temperature range during its transmission cycle. The minimum growth temperature of A. butzleri was initially reported to be 15°C [11]. Later, some studies reported lower limits as 10°C; for example, in Ellinghausen McCullough Johnson Harris medium [12] and in chicken meat juice, as well as in Brain Heart Infusion (BHI) broth [13]. Van Driessche and Houf [14] investigated the survival capability of A. butzleri in water with/without organic material at minimum 4°C and reported that all tested A. butzleri strains survived for at least 203 days when organic material is present in the water, indicating the best cold adaptation among all human-related Arcobacter species. With the complete genome of the A. butzleri RM4018 sequenced in 2007 [15], the understanding of adaptation to environmental stress could be improved. To date, no data describing the cold-shock response of Arcobacter spp. have been reported. Because previous phenotypic studies suggest that A. butzleri could adapt to cold temperatures, the presence of cold-related genes is presumed. The function of the cold-related proteins is best studied in Escherichia coli. Jones et al. [16] first reported that, after a cold shock from 37°C to 1...