Determination of Differentially Expressed Genes Involved in Arabinoxylan Degradation by Bifidobacterium longum NCC2705 Using Real-Time RT-PCR.

Real-time quantitative PCR (qRT-PCR) can be used to monitor specific catabolic activity by gene transcriptional analysis of bacterial cultures. This methodology has been applied to determine if the differential expression of genes putatively involved in arabinoxylan degradation by Bifidobacterium longum NCC2705 could be associated to the consumption of this prebiotic. Three genes putatively encoding arabinofuranosidases (abfI, abfA, and abfB) and one putatively encoding endoxylanase (xynD) were targeted for this purpose. Bifidobacterium longum NCC2705 exhibited higher growth yield relative to glucose based on viable counts or optical density for arabinoxylan as compared to xylose and arabinose. Among reference genes studied (16S rRNA, tufA, recA, rpoB, and atpD) the most stably expressed genes were rpoB, tufA, and atpD. The most significant increase in target gene expression was observed in the presence of arabinoxylan for the xynD gene, while xylose and arabinose had a weaker effect on xynD expression. In conclusion, B. longum NCC2705 overexpresses an endoxylanase gene in response to arabinoxylan.