1H NMR-based metabolomics approach to understanding the temperature-dependent pathogenicity of Lactococcus garvieae

Lactococcus garvieae is known as main agent of the bacterial diseases, Lactococcosis in trout farms. The present study was aimed to study the metabolic bases of the temperature-dependent pathogenicity of the L . garvieae using 1H NMR spectroscopy. The bacteria were grown at different temperatures, including 10, 14, 18 and 22˚C and then the metabolites extracted, identified and quantified. The results of PLS-DA analysis clearly separated the experimental treatments. The main metabolites responsible for this separation were acetate, acetoacetate, creatine phosphate, succinylacetone and trehalose. Furthermore, the result of the analysis of variance indicated also significant differences in metabolome content between temperature treatments. The bacteria exposed to higher temperatures showed more concentration of acetate and acetoacetate compared to those grown at 10°C. The concentrations of trehalose were higher in the bacteria grown at 14 and 18°C compared to other temperature treatments. The higher levels of succinylacetone were found in the bacteria exposed to the temperature less than 14°C compared to those grown at 18 and 22°C. The creatine phosphate concentrations increased with temperature, however, a significant decline occurred at 22°C. The levels of isoeugenol, methionine and betaine significantly declined with increase of temperature from 10 to 22°C. Also, the concentration of N-Acetylglutamine significantly raised as the temperature increased from 10 to 22°C. In conclusion, the temperature altered the metabolome of L. garvie , which this may be linked to the pathogenicity. The temperature probably affects fermentation, homeostasis, energetic condition and metabolism of amino acids in L. garvieae .