Observation of tetrahydrofolylpolyglutamic acid in bacteria cells by matrix-assisted laser desorption/ionization mass spectrometry

Tetrahydrofolylpolyglutamic acid in whole bacteria cells and cell lysates is analyzed by matrix-assisted laser desorption/ionization mass spectrometry. The speed, mass information, and tolerance to impurities of this technique make it ideal for monitoring the glutamation levels of folic acid in biological systems. Folylpolyglutamic acid is observed in a few strains of E. coli and two species of Staphylococcus bacteria. The effects of growth time, growth media, and the addition of methotrexate, a dihydrofolate reductase inhibitor, are also studied.