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The aim of this study was to characterize the stress response of C. jejuni, C. coli and C. lari to elevated temperatures. C. coli and C. lari show a decreased ability to survive at 46 °C in comparison to C. jejuni. The differential expression of heat-shock genes by real-time qPCR could not explain the phenotypic differences. Therefore, the changes in global gene expression at 46 °C compared to 37 °C in C. jejuni, C. coli and C. lari was investigated by RNA sequencing (RNA-Seq). This analysis confirmed and extended the knowledge of the heat-shock response of C. jejuni generated in earlier studies by using other methods such as microarray and RT-qPCR. Furthermore, this work provides first insights on the heat shock response on the transcriptional level of C. coli and C. lari.
The RNA-Seq data show significant differences in the temperature-dependent regulation of gene expression. While in C. coli and C. lari 9 % of the genes showed a significant change in expression, this proportion in C. jejuni is only 3 %. In C. jejuni 89 % of the regulated genes show an increased transcription rate, while 45 % of the regulated genes in C. coli and 69 % in C. lari are upregulated. The percentage of genes whose expression is regulated in all three species alike, is very low. A categorization of the differentially expressed genes reveals that their products were distributed over almost all functional groups. Particularly genes encoding cell membrane proteins, protein metabolism, the protein biosynthesis and transport and binding proteins, show an increased expression.
The potential of RNA-Seq is not the precise quantitative determination of gene expression, but in its potential to decipher the architecture of the transcriptome and possible regulatory components. RNA-Seq experiments, as the future standard in the field of gene expression analysis, could also play an important role in food microbiology to understand the survival of microorganisms and their adaptation to sublethal factors in the food chain.