Response Regulator CitT from CitST Two-Component System Specifically Regulates the Pectin Degradation in Bio-Degumming of Ramie Fibers by Bacillus subtilis

Abstract

CitST is a typical two-component regulatory system that can regulate citrate utilization and is involved in the regulation of carbohydrate metabolism in Bacillus subtilis. B. subtilis is a kind of dominant species to bio-degum ramie fibers, which could degrade and utilize non-cellulose components as a carbon source during bio-degumming. This study aimed to explore the regulatory function of response regulator CitT from CitST two-component system when B. subtilis was used for extracting ramie fibers. The results showed that gene knocked-out of citT could significantly decrease the bio-degumming ability of B. subtilis. The enzymatic activity mensuration of functional enzymes revealed that deficient in CitT would remarkably reduce the enzymatic activity of pectinase, but there was a little difference in transcriptional levels of their encoding genes with qRT-PCR analysis, which further demonstrated that it was a lack of correlation between mRNA expression and enzymatic activities. The data also reflected that CitT specifically regulated the pectin degradation in bio-degumming of ramie fibers by analyzing the polysaccharide degradation rates of gum components. In conclusion, it was shown for the first time that CitT probably positively regulated the bio-degumming of ramie fibers and was an important regulator in pectin degradation.

Keywords

• response regulator citt
• ramie bast
• bacillus subtilis
• bio-degumming
• polysaccharide metabolism
• pectin biodegradation