Unravelling Serpin Regulation in Bifidobacterium Longum NCC 2705

Résumé du livre

The final experimental chapter deepened our understanding of the carbohydrate substrate-based regulation mechanisms in B. longum NCC 2705. Comparing glucose and galactose grown cells, we noted that serpin mRNA and protein levels did not correlate with each other, pointing to the involvement of a post-transcriptional regulatory mechanism. Combining transcriptome data and RNA-RNA interaction prediction tools, we identified a trans-acting sRNA encoded in the conserved intergenic 16S-23S rRNA genomic region, that we named sBLO-161. This sRNA is predicted to efficiently bind by its 5’ and 3’ ends to the serpin (BL0108) mRNA and to form two internal stem-loops that could inhibit translation of the targeted mRNA. Strikingly, in silico analysis predicted sBLO-161 to form highly similar RNA-duplex structures with a range of mRNAs spread throughout the genome of NCC 2705, suggesting that it might control additional important functions, including stress response, cell wall synthesis, and carbohydrate transport and metabolism. Furthermore, we could demonstrate that the activity of the key central carbon metabolism enzyme fructose-6-phosphoketolase on glucose or galactose reflected its predicted sBLO-161-dependent post-transcriptional regulation. Taken together, we describe the first bifidobacterial sRNA that is predicted to exert a global regulatory function in B. longum NCC 2705.