Unusual strains of the bacteria Escherichia coli (E. coli), which was once believed to hardly survive in the external environment, were previously discovered in marine intertidal sediment in Hong Kong and named UNISED. The metabolome expressed by E. coli UNISED and its special metabolic adaptation to its external environment remains unknown. Currently, liquid chromatography – tandem mass spectrometry (LC-MS/MS) based metabolomics is becoming a promising tool for bacterial strain discrimination and biomarker discovery. In this context, we adapted an untargeted LC-MS/MS metabolomics approach combing RPLC and HILIC technologies to investigate three biofilm-forming strains, E. coli UNISED 3356, 3659 and 5028, as well as the model strain E. coli K-12 MG1655 as a control group. This method al...[ Read more ]

Unusual strains of the bacteria Escherichia coli (E. coli), which was once believed to hardly survive in the external environment, were previously discovered in marine intertidal sediment in Hong Kong and named UNISED. The metabolome expressed by E. coli UNISED and its special metabolic adaptation to its external environment remains unknown. Currently, liquid chromatography – tandem mass spectrometry (LC-MS/MS) based metabolomics is becoming a promising tool for bacterial strain discrimination and biomarker discovery. In this context, we adapted an untargeted LC-MS/MS metabolomics approach combing RPLC and HILIC technologies to investigate three biofilm-forming strains, E. coli UNISED 3356, 3659 and 5028, as well as the model strain E. coli K-12 MG1655 as a control group. This method allowed for the detection of more than 10000 features for each bacterial strain. More than 100 metabolites were identified based on MS/MS spectral matches. LC-MS/MS profiling and multivariate analysis PCA and sPLS-DA indicated that the four E. coli strains could be differentiated at strain level by metabolomics. Subsequently, discriminating features were selected based on volcano plots and PLS-DA model. Further analysis indicated a lower abundance of most discriminating features in environmental strains, suggesting that the E. coli environmental strains may lower most of their metabolite expression to survive in the external environment.