Exploring the Cellulose Degradation Machinery of Hot Springs Bacteria
Members of the Caldicellulosiruptor genus of bacteria, originally discovered in terrestrial hot springs, are unique in their ability to efficiently degrade cellulosic plant biomass at temperatures over 70°C. Researchers at the DOE Bioenergy Science Center (BESC) at Oak Ridge National Laboratory previously sequenced the genomes of several Caldicellulosiruptor species and characterized their abilities to degrade corn stover, switchgrass, and other biomass feedstocks. In a new study, BESC scientists used mass spectrometry-based proteomics to compare the complex mixture of enzymes secreted by two Caldicellulosiruptor species during cellulose degradation. Both of the organisms deployed carefully regulated configurations of multifunctional cellulase modules, tethered cellulose binding elements, and proteins that bind released sugars and return them to the cell. All of these elements were traced back to encoding genes on sequenced genomes. The secreted cellulase fractions from the Caldicellulosiruptors were found to work optimally at 85°C and pH 5, indicating significantly higher thermal stability and acid tolerance than current commercially available cellulase cocktails. These results present a promising source of novel cellulase enzymes for industrial development and provide new insights into the diversity of tools that microbes have at their disposal for biomass breakdown.
Lochner, A., R. J. Giannone, M. Rodriguez, Jr., M. B. Shah, J. R. Mielenz, M. Keller, G. Antranikian, D. E. Graham, and R. L. Hettich. 2011. “Use of Label-Free Quantitative Proteomics To Distinguish the Secreted Cellulolytic Systems of Caldicellulosiruptor bescii and Caldicellulosiruptor obsidiansis,” Applied and Environmental Microbiology 77, 4042–54. DOI: 10.1128/AEM.02811-10.