The molecular mechanism and post-transcriptional regulation characteristic of Tetragenococcus halophilus acclimation to osmotic stress revealed by quantitative proteomics.

UNLABELLED

Tetragenococcus halophilus is a moderate halophilic bacterium which was widely used in fermentation processes, growing in a broad range of salinity conditions, and can survive a saturated 26.47% w/w NaCl concentration. However, the mechanism of this outstanding ability to acclimate to extracellular osmotic stress still remains unknown. The current study firstly conducted a quantitative proteomic analysis to identify alterations of the cellular proteome under both hypo-osmotic and hyper-osmotic stress conditions. A total of 1405 proteins were identified and differentially accumulated proteins were analyzed, further functional annotations were performed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. The results revealed that both hypo- and hyper-osmotic stresses have prominent impacts on the synthesis of proteins involving in multiple cellular functions. Further analyses of the differentially accumulated proteins suggested that the adaptation strategies T. halophilus applies to deal with hypo- and hyper-osmotic stress conditions may be distinct. Comparison of the differentially accumulated proteins in both transcriptomic and proteomic study indicated the existence of post-transcriptional modification during salinity adaptation of T. halophilus. The current study generated a proteomic atlas of differentially accumulated proteins under both hypo- and hyper-osmotic stress conditions, provided an overview of the molecular mechanism of osmotic acclimation of T. halophilus.

SIGNIFICANCE

The current study aimed to reveal how the moderately halophilic Tetragenococcus halophilus adapt to extracellular salinity stress, which is the first proteomic study analyzing the differences in proteome of Tetragenococcus halophilus between hypo- and hyper-osmotic stress to our knowledge. By analyzing the differences in the accumulating levels of the proteome via isobaric labeling-based quantitative proteomic study, we identified proteins with significantly different accumulation levels which may play important roles in the adaptation process to extracellular salinity stress. Examining the cellular functions of these proteins according to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, a draft view of how the bacterium act to acclimate to osmotic stress has been drawn. Further analysis revealing the differences between the transcriptome and proteome suggested that some proteins may undergo post-transcriptional regulation during acclimation process, which still remains unstudied and needs further investigations. The results of the current study can help researchers to gain insights and further reveal the halophilic mechanism of halophiles.