Proteômica global de Campylobacter jejuni NCTC11168 sob diferentes condições de pH

Abstract

Thermophilic Campylobacter is a subgroup within the genus Campylobacter,formed by the species C. jejuni, C. coli, C. lari and C. upsaliensis, being so namedbecause of its optimal multiplication temperature oscillating between 42 °C. Thermophilic Campylobacter are currently the leading foodborne disease215 causing bacteria worldwide, as well as being among the top four global causes of diarrheal disease. Among the thermophilic Campylobacter species, the most related to campylobacteriosis is C. jejuni, followed by C. coli. The main reservoir of C. jejuni are birds, mainly poultry, possibly because the body temperature of these animals is similar to the optimal temperature for their multiplication. Despite the importance of this pathogen for public health, little is known about the survival and infection mechanisms of C. jejuni. Thus, the objective of this study was to evaluate the global proteomics of C. jejuni NCTC11168 when subjected to different pH conditions, simulating the barriers found in the human organism and in chicken meat cuts. For this, the standard strain C. jejuni NCTC 11168 was submitted to different pH values, in order to make the in vitro environment similar to gastric pH (pH 4.0 - the most acidic in which there was microbial multiplication in previous tests), to the average pH of chicken meat cuts (pH 5.8) and to the human intestinal pH (pH 8.0). Proteins were extracted by the single spot technique (SP3) and the separation, identification and quantification of proteins was performed by liquid chromatography coupled to mass spectrometry. It was observed that there was a significant difference in the synthesis of proteins, in the different pH conditions tested. It was found that pH 5.8 was the one that most favored the synthesis of proteins related to the defense mechanisms of C. jejuni, which is an interesting finding since it is the pH found in chicken meat cuts, wh may be a factor that benefits the pathogen survival and consequently provide the campylobacteriosis spread. In addition, increase in the abundance of two proteins responsible for energy generation via anaerobic respiration (NapA and FrdA) was identified when at pH 8.0, suggesting that intestinal pH induces an increase in the activity of the electron transport chain, probably in order to to guarantee the cytoplasmic homeostasis of C. jejuni. From the results obtained in the present study, it was possible to prove that somehow the stress response proteins (thermal and oxidative) are also involved in the C. jejuni acid stress response. In addition, it was possible to verify that among the evaluated pH, pH 5.8 was the most expressive in terms of responses to acid stress, being a good condition to be worked on in future research, in order to have a better knowledge about of the interference of pH in the C. jejuni pathogenesis.