INTRACELLULAR COMPOUNDS QUANTIFICATION BY MEANS OF FLOW-CYTOMETRY IN BACTERIA - APPLICATION TO XANTHAN PRODUCTION BY XANTHOMONAS-CAMPESTRIS

The use of flow cytometry (FCM) to quantitatively analyze intracellula r compounds is studied. FCM is a very useful technique for individual cell studies in microbial systems, and gives access to information whi ch cannot be obtained in any other way. Nevertheless, it provides data in arbitrary units, that is, relative data. This analytical technique could be employed for kinetic modeling of microbial systems and even for internal phenomena analysis, but for this purpose, absolute data-t hat is concentration of intracellular compounds-must be used. In this work, relative flow cytometry data are transformed into absolute data by means of calibrations employing the same fluorochromes with another technique: spectrofluorymetry. Calibrations of DNA, RNA, and protein intracellular concentrations are presented for the bacteria, Xanthomon as campestris. Other analytical methods, based on biochemical determin ations, were also employed to quantify intracellular compounds, but th e results obtained are very poor compared with those achieved by means of spectrofluorymetry (SFM). Calibration equations and data obtained by both techniques are given. Evolutions of protein and nucleic acids during Xanthomonas campestris growth and xanthan gum production are sh own. (C) 1998 John Wiley & Sons, Inc.