The experiments of real-time PCR shown in Figure 6B demonstrated that rRNA16S was amplified after $17 cycles while the amplification of fucA1 mRNA was observed after 38 cycles, despite the fact that we used $2500-fold more cDNA for the amplification of fucA1. This indicates that the gene fucA1 is transcribed at very low level. No significant differences in the fucA1 mRNA level were observed in cells grown in YSM or YGM media. This is further confirmed by the analysis by western blot of the extracts of the same cells of S.solfataricus used to prepare the total RNAs, which revealed equal amounts of a-fucosidase in the two extracts ( Figure 6C) . Therefore, the low a-fucosidase activity observed under the conditions tested is the result of the poor transcription of the fucA1 gene.