NMR analysis of metabolic responses to extreme conditions of the temperature-dependent coral pathogen Vibrio coralliilyticus

Abstract

To identify and understand the presence of metabolites responsible for the variation in the metabolic profile of Vibrio coralliilyticus under extreme conditions. Multiple batches of V. coralliilyticus were grown under normal conditions. Four samples in one batch were subjected to extreme conditions via a freeze-thaw cycle during lyophilization. Polar metabolites were extracted using a combination of methanol, water and heat. Nuclear magnetic resonance (NMR)-based metabolic profiles indicated significant differences between the normal and stressed samples. Three compounds identified in the stressed metabolome were maltose, ethanolamine, and the bioplastic-type compound (BTC) 2-butenoic acid, 2-carboxy-1-methylethyl ester. This is the first report of the production of this BTC by V. coralliilyticus. The presence of maltose and ethanolamine indicates a state of acute nutrient limitation; therefore, we hypothesize that the cell's metabolism turned to its own cell wall, or perhaps neighbouring cells, for sources of carbon and nitrogen. The presence of the BTC also supports the acute nutrient limitation idea because of the parallels with polyhydroxyalkanoate (PHA) production in other gram-negative bacteria, including other Vibrio species. Recent metabolomics research on the temperature-dependent coral pathogen V. coralliilyticus has led to the discovery of several compounds produced by the organism as a response to high density, low nutrient conditions. The three metabolites, along with (1) H NMR metabolic fingerprints of the nutrient limited samples, are proposed to serve as metabolic markers for extremely stressful conditions of V. coralliilyticus.