Response to Cold Adaption in Acinetobacter johnsonii XY27 from Spoiled Bigeye Tuna (Thunnus obesus): Membrane Protein Composition and Protein Biomarker Identification by Proteomics

Acinetobacter johnsonii is one of the major food-spoilage bacteria and can survive under cold stress. In this study, the membrane composition, membrane permeability, and energy transduction of A. johnsonii XY27 cultured at 4 and 30 degrees C were examined comparatively by flow cytometry combined with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. The Na+/K(+)ATPase activity, alkaline phosphatase and ATPase activity, fluorescence intensity, and cell viability in A. johnsonii XY27 increased with the decrease in cultivation temperature. The polyunsaturated fatty acid and monounsaturated fatty acids have a higher content in A. johnsonii XY27 cultured at 4 degrees C compared to that cultured at 30 degrees C, in which the contents of methyl palmitoleate, methyl myristoleate, and methyl oleate increased dramatically with decreasing temperature. Comparative proteomics analysis revealed that 31 proteins were downregulated and 4 proteins were upregulated, in which catalase-peroxidase 1 and cold shock proteins as biomarker proteins could effectively control A. johnsonii during cold adaptation.

Automated summary

In this study, the membrane composition, membrane permeability, and energy transduction of A. johnsonii XY27 cultured at different temperatures were investigated. The results showed that the activity of Na+/K(+)ATPase, alkaline phosphatase, ATPase, fluorescence intensity, and cell viability increased with decreasing temperature. The fatty acid composition also changed, with higher content of polyunsaturated fatty acids and monounsaturated fatty acids at lower temperatures. Moreover, specific proteins were identified as biomarkers for controlling the growth of A. johnsonii during cold adaptation.