Transcriptional profiling of biomass degradation-related genes during Herbivorax saccincola A7 growth on different carbon sources

Herbivorax saccincola A7 is an alkali-thermophilic lignocellulolytic bacterium that was known to possess a strong xylan degradation ability. They can utilize a wide range of carbon sources, however the response and regulation mechanisms to different carbon sources, in terms of genes expression, are still not identified. In this study, H. saccincola A7 was cultured with cellobiose, cellulose, xylan, cellulose-xylan mixture, and empty fruit bunch (EFB) as the sole carbon source. We carried out a comparative expression analysis, focusing on biomass degradation-related genes. The cellulosomal scaffolding proteins and cellulosomal enzymes of H. saccincola A7 were drastically induced when a cellulose-containing substrate was used as a carbon source. On the other hand, xylan induced only some non-cellulosomal enzymes that might be necessary for xylan degradation. The identification of the carbohydrate-sensing mechanism in H. saccincola A7 appeared a similar system as previously described in Clostridium thermocellum. The lignocellulose degradation ability of H. saccincola A7 may be controlled enzyme expression by cellulose-containing substrate, not by xylan. Thus, recognition in the existence of cellulosic substrates is effective in enhancing a high xylan degradation ability in H. saccincola A7. The 5 samples were analyzed. H. saccincola A7 cell growth on different carbon sources were used to extracted total RNA for gene expression analysis. We examined the selection of the calibrator gene and found that Triosephosphate isomerase (Tpi) is the best calibrator gene for H. saccincola A7