Transformable facultative thermophile Geobacillus stearothermophilus NUB3621 as a host strain for metabolic engineering.

Metabolic engineers develop inexpensive enantioselective syntheses of high-value compounds, but their designs are sometimes confounded by the misfolding of heterologously expressed proteins. Geobacillus stearothermophilus NUB3621 is a readily transformable facultative thermophile. It could be used to express and properly fold proteins derived from its many mesophilic or thermophilic Bacillaceae relatives or to direct the evolution of thermophilic variants of mesophilic proteins. Moreover, its capacity for high-temperature growth should accelerate chemical transformation rates in accordance with the Arrhenius equation and reduce the risks of microbial contamination. Its tendency to sporulate in response to nutrient depletion lowers the costs of storage and transportation. Here, we present a draft genome sequence of G. stearothermophilus NUB3621 and describe inducible and constitutive expression plasmids that function in this organism. These tools will help us and others to exploit the natural advantages of this system for metabolic engineering applications.