transcription these primers consist of an equimolar mixture of random hexamers and random octamers the random primers are synthesized by mwg ebersberg germany the incorporation of the fluorescent dyes and the purification of the labeled cdna is done using the atlas u2122 glass fluorescent labeling kit cat no k1037 1 clontech heidelberg germany following the manufacturers instructions using the described protocol the cdna of the no l lysine producing strain atcc13032 is labeled with the fluorescent dye cy3 the cdna of the l lysine producing strain atcc21513 is labeled with the fluorescent dye cy5 as described in example 3 for each strain the total cellular rna is isolated and labeled at different time points during the fermentation for the analysis of differences in the transcriptional status the labeled cdna of both strains is hybridized competitively for each time point on the arrays described in example 1 for the experienced user beneath other sources the principles and further technical and methodological details are described in the book of m schena dna microarrays editor m schena oxford university press 1999 the hybridization is done using the atlas u2122 glass hybridization chamber and glasshyb solution catalog numbers 7899 1 and 8016 1 clontech heidelberg germany the slides are scanned using a scanarray 4000 confocal microarray scanner gsi lumonics billerica mass usa following the manufacturers instructions the acquired images are further analyzed using the quantarray software provided together with the scanner the fluorescence intensity for each spot and each fluorescence dye is calculated separately the results of each data point of the single experiments are plotted against each other signals that give a data point that is more than a factor of 1 5 away from the correlation.