Monitoring the growth of a bacteria culture by MALDI-MS of whole cells

We have probed the time evolution of a growing bacteria culture by extracti ng samples periodically and performing matrix-assisted laser desorption/ion ization mass spectrometry (MALDI-MS) on whole cells. The mass spectra gener ated by this method contain tens of peaks in the 3-11-kDa mass range. Cultu res of E. coli strain K-12 were grown in two types of containers and at two nutrient concentrations and sampled periodically from 6 to 84 h after inoc ulation. The relative intensities of several of the stronger peaks vary qui te dramatically as a function of time. These temporal characteristics must be taken into account when MALDI-MS is applied to identify bacteria. The re sults also suggest that MALDI-MS can be used to follow the aging of a bacte ria culture.