Non-canonical resource allocation in heterotrophically growing Thermoanaerobacter kivui

Allocation of resources in the costly proteome reflects trade-offs between cellular functions. For example, proteome composition of Escherichia coli is significantly regulated by growth rate. An increasing anabolic, especially ribosomal, proteome fraction correlates with a decreasing catabolic proteome fraction at faster growth, which then leads to changes in catabolism. Our systems-level studies of the thermophilic acetogen Thermoanaerobacter kivui when growth rate is varied over two orders of magnitude revealed a different strategy: proteome allocation is only partially controlled by growth rate, and metabolic rates are primarily controlled posttranslationally. At slower growth, ribosome numbers are controlled by rRNA concentrations with an excess of ribosomal proteins. Composition of the catabolic proteome is uncoupled from catabolic rates as indicated by flux analysis. This study adds to the understanding of acetogenic Clostridia, which are of interest for biotechnological processes in a carbon-neutral economy, and points to a complex landscape of microbial ecophysiological strategies.