Pre-separation and pre-concentration of bacteria is an important step especially when they are uncultured and bacterial concentration in the matrix is low. This study describes a preparative method based on isoelectric focusing of colored microorganisms in a cellulose-based separation medium from a high conductivity matrix. The isoelectric points found for the examined cells were 1.8 for Micrococcus luteus, 3.5 for Dietzia sp., and 4.7 for Rhodotorula mucilaginosa using capillary isoelectric focusing. The final positions of the zones of colored microbial cells in the cellulose-bed are indicated by colored pI markers. Segments of the separation medium with cells were harvested by a spatula, simply purified using centrifugation and analyzed by capillary isoelectric focusing and matrix-assisted laser desorption/ionization time of flight mass spectrometry. The determined recovery ranged from 78% to 93%. The viability of the harvested cells was verified by their cultivation.

Institute of Analytical Chemistry of the CAS v v i Veveří 97 602 00 Brno Czech Republic

The Department of Microbiology Faculty of Medicine Masaryk University Kamenice 53 5 625 00 Brno Czech Republic

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Isoelectric Focusing Fractionation Method for Signal Enhancement in Detection of Inactivated Biological Agents Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry