Verification of gene expression profiles by Northern blots. Eleven genes were selected randomly to compare their expression profiles obtained with DNA microarray with expression in Northern blots. The intensity of the bands in Northern blots was calculated using ImageJ and normalized to the value of the histone H1 gene as internal control. The log ratio of expression values in comparisons A, B and C is shown in grey for microarray and black for Northern blots. The correlation coefficient was calculated using the Excel function. Numbers on top indicate the probed genes: 1, act15 (DDB0185015); 2, sevA (DDB0188380); 3, arcB (DDB0204976); 4, coaA (DDB0192207); 5, talA (DDB0219577); 6, eIF6 (DDB0203843); 7, gadB (DDB0188068); 8, aclyB (DDB0205386); 9, (DDB0219898); 10, rabR (DDB0168590); 11, nramp1 (DDB0202615).