The social evolution of stable butanol production in Clostridia

C1 gases present in syngas and various industrial off-gases are promising feedstocks for the biological production of chemical commodities. Among these, carbon monoxide (CO) is often the most abundant. However, due to its high toxicity CO can only be utilised by a limited number of industrially relevant organisms. For instance, while it can serve as a substrate in anaerobic gas fermentation processes, it cannot be utilised by Cupriavidus necator, one of the most promising aerobic C1 platform organisms presently available.

The aim of this studentship is therefore to metabolically engineer C. necator so that it can efficiently grow on CO containing waste gases and convert these into desirable chemicals. This will be achieved through (i) isolation of CO-resistant mutant strains, (ii) introduction of CO-utilisation genes from other species, (iii) isolation and high throughput in vitro evolution of CO utilising strains and (iv), further targeted engineering of well performing strains following their genomic, transcriptomic and physiological characterisation.

Biological utilisation of CO requires its efficient oxidation to CO2 by CO dehydrogenases (CO DHs). Aerobic CO DHs are enzymes which acquire functionality through a complex maturation process relying on numerous accessory proteins. Furthermore, respiratory chain components and hydrogenases are highly sensitive to CO in many bacteria. Thus, equipping a bacterium with the ability to grow on CO is not a trivial task. Fortunately, however, the required genes are often present in the form of defined clusters, such as those found on the megaplasmid pHCG3 in the aerobic CO oxidising bacterium Oligotropha carboxidovorans. These will be transferred into C. necator and utilised as outlined above.