This article details a method for extracting metabolites from Staphylococcus aureus using liquid chromatography-mass spectrometry. The protocol emphasizes maintaining low temperatures to preserve metabolic states and minimize degradation during the extraction process.
Begin with Staphylococcus aureus suspended in a quenching solution containing silica beads, stored at a low temperature to preserve its metabolic state.
Homogenize the bacteria under cold conditions to release intracellular contents while minimizing enzymatic degradation of metabolites.
Centrifuge the lysate and harvest the metabolite-rich supernatant.
Add an organic solvent to the extract and vortex to precipitate macromolecules from soluble metabolites.
Centrifuge to pellet the precipitate and transfer the supernatant into vials.
Load the vials into a liquid chromatography-mass spectrometry system.
Inside the chromatography column, metabolites interact with the solid stationary phase based on their chemical properties.
Add a buffer to elute the metabolites. Then, direct the metabolites into the mass spectrometer’s electrospray ionization source to ionize them.
The ions are then separated based on their mass-to-charge ratios.
The resulting data is compared to a reference database to identify the metabolites.
To begin the metabolite extraction, first thaw the samples on wet ice. Then disrupt the cells in a homogenizer with four 30-second bursts at 6000 rpm, with two minute cooling periods on dry ice between cycles.
Clarify the lysates for 15 minutes in a pre-chilled refrigerated microcentrifuge tube at maximum speed. Following centrifugation, transfer the supernatant to a clean microcentrifuge tube. Using a micropipette, transfer a small portion of the sample to a microcentrifuge tube for quantification of residual peptide content as described in the text protocol.
Store the remainder of the sample at minus 80 degrees Celsius. Refer to the text protocol for analysis of the metabolites via liquid chromatography and mass spectrometry.
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