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.

Keywords: A. butzleri; cold adaptation; cold shock-related genes; temporal transcriptional expression.

Fig. 1

Growth curve of five A. butzleri isolates with no growth capability at 8 °C, shown as the median ± interquartile range (n = 3).

Fig. 2

Growth curve of three A. butzleri isolates at 8 °C, shown as the median ± interquartile range (n = 4).

Fig. 3

Temporal expression pattern of 13 cold‐related genes in three A. butzleri isolates after a temperature downshift to 8 °C. The expression level was analyzed by RT‐qPCR and is shown as the median ± interquartile range of log₂ fold changes (n = 3). The dotted lines show the threshold (−1 to 1) for the relevant up‐ and down‐regulation. Similar expression pattern were analyzed by K‐means clustering. Cluster I includes genes with high up‐regulated expression (A), cluster II includes those with moderate up‐regulated expression (B) and cluster III includes those with non‐regulated expression (C) in all three A. butzleri strains. (D) Genes belonging to different clusters in strain H1, H2 and C2. Statistical significant difference between strain H1 and H2 (a), H1 and C2 (b) or H2 and C2 (c): *P < 0.05, **P < 0.01 (analyzed by two‐way analysis of variance).