WHAT IT PRODUCES
- the bacterium produces acetate, pyruvate, and lactate when grown on monosaccharides and soluble cellulosic carbon sources.
GROWTH & DEGRADATION MECHANISM
- 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of AFEX-treated corn stover was associated with release of glucose and xylose monosaccharides (Gardner and Keating, unpublished), suggesting that cellulose and hemicellulose were used as carbon sources.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
- the bacterium contains the complete repertoire of enzymes required to degrade plant cell wall and storage polysaccharides. Approximately one-third of these putative proteins (57) are predicted to contain carbohydrate binding modules derived from 13 of the 49 known families. Sequence analysis reveals approximately 130 predicted glycoside hydrolases that target the major structural and storage plant polysaccharides. In common with that of the colonic prokaryote Bacteroides thetaiotaomicron, the genome of C. japonicus is predicted to encode a large number of GH43 enzymes, suggesting that the extensive arabinose decorations appended to pectins and xylans may represent a major nutrient source, not just for intestinal bacteria but also for microorganisms that occupy terrestrial ecosystems. The results presented here predict that C. japonicus possesses an extensive range of glycoside hydrolases, lyases, and esterases. Most importantly, the genome of C. japonicus is remarkably similar to that of the gram-negative marine bacterium, Saccharophagus degradans 2-40(T). Approximately 50% of the predicted C. japonicus plant-degradative apparatus appears to be shared with S. degradans, consistent with the utilization of plant-derived complex carbohydrates as a major substrate by both organisms.
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.
HOW TO MEASURE
- Use kits to measure organic acid concentrations
SOURCES
http://aem.asm.org/content/76/15/5079.full
http://onlinelibrary.wiley.com/doi/10.1111/mmi.12821/abstract