Deconstruction by C. thermocellum—from microbe mediated to dynamic redistribution of cellulosomes

TL;DR

This paper shows how Clostridium thermocellum dynamically redistributes cellulosomes during biomass deconstruction, shifting from microbe-mediated to substrate-associated strategies.

Contribution

The study reveals a dynamic redistribution of cellulosomes during growth on insoluble substrates using super-resolution imaging and machine learning.

Findings

C. thermocellum initially retains cellulosomes on the cell surface.

Later, large cellulosome clusters are relocated to the biomass interface.

This shift indicates a functional transition to substrate-associated degradation.

Abstract

By combining super-resolution imaging and machine learning to study the dynamics of biomass deconstruction by C. thermocellum, we show that this deconstruction goes from a microbe-mediated strategy to a dynamic redistribution of cellulosomes during growth on insoluble substrates.

Clostridium thermocellum is one of the most efficient microorganisms for the deconstruction of cellulosic biomass. To achieve this high level of cellulolytic activity, C. thermocellum uses large multienzyme complexes known as cellulosomes to break down complex polysaccharides, notably cellulose, found in plant cell walls. The attachment of bacterial cells to the nearby substrate via the cellulosome has been hypothesized to be the reason for this high efficiency. The region lying between the cell and the substrate has shown great variation and dynamics that are affected by the growth stage of cells and the substrate used for growth. Here, we used both super-resolution imaging and machine-learning approaches to study the distribution of C. thermocellum cellulosomes at different stages of growth. We show that C. thermocellum initially retains its cellulosomes primarily on the cell surface but then relocates large cellulosome clusters to the interface with biomass, therefore depleting its cell surface of cellulosomes. These results indicate dynamic redistribution of cellulosomes during growth, with a functional shift toward substrate-associated degradation later during growth on biomass.

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