Climate change has illuminated a need for finding an alternative, renewable, carbon-neutral source of producing valuable products such as biofuels, chemicals, and other materials, as our limited supply of fossil fuels is rapidly depleting. Lignocellulosic biomass (LCB) is the most abundant carbon source on the planet, and thus is an attractive precursor for many valuable materials. Several anaerobic organisms, including Clostridium thermocellum (Ct), have adapted the ability to efficiently break down LCB into its constituent building blocks. To better understand the biomass degradation mechanisms deployed by Ct, we are pursuing cryoEM-driven visual proteomics of large assemblies Ct is secreting during growth with LCB as a food source. We biochemically isolated exoproteomic samples from Ct undergoing active biomass degradation and performed electron microscopy, which revealed filamentous assemblies that appear to be composed of regular repeating globular units. As part of our visual proteomics approach, we also harnessed the analytical power of mass spectrometry to reveal a number of components present in the isolated complexes that may be involved in cellulose degradation. A complete understanding of the molecular architecture of such cellulose-degrading complexes in their native form will facilitate better insights into this complex process and allow for researchers to engineer these organisms and assemblies toward improved and efficient ways of LCB degradation.
Agdanowski et al. (Sun,) studied this question.