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- C. japonicus is able to utilize corn stover and switchgrass as sole sources of carbon and energy for growth.
- corn stover and switchgrass subjected to the AFEX process
- When added to M9 minimal medium, the washed, autoclaved, AFEX-treated corn stover (or AFEX-treated switchgrass) failed to support the growth of E. coli but allowed the growth of C. japonicus (Fig. 2 A). Growth of C. japonicus in the presence of AFEX-treated corn stover was associated with release of glucose and xylose monosaccharides (Gardner and Keating, unpublished), suggesting that cellulose and hemicellulose were used as carbon sources.
- corn stover and switchgrass subjected to the AFEX process
- efficient cellulase secretion and growth on biomass are prevented by disruption of the type II secretion system
- suggests that C. japonicus utilizes a combination of hydrolytic and oxidative cleavage mechanisms to degrade cellulose
GENETIC MANIPULATION
- C. japonicus can be metabolically engineered using broad-host-range plasmids.
- We developed tools for directed gene disruptions in C. japonicus and used this system to construct a mutant in the gspD gene, which is predicted to encode a component of the type II secretion system. The gspD::pJGG1 mutant displayed a greater-than-2-fold decrease in endoglucanase secretion compared to wild- type C. japonicus. In addition, the mutant strain showed a pronounced growth defect in medium with biomass as a carbon source, yielding 100-fold fewer viable cells than the wild type.
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