Introduction: Formate is an important intermediate in the metabolism of different anaerobic bacteria and can be used as feedstock to produce valuable chemicals. The thermophilic acetogenic bacterium Thermoanaerobacter kivui grows by producing acetate from formate, but formate can also exclusively be oxidized to H2 + CO2 [1] and vice versa, by the action of the hydrogen-dependent CO2 reductase (HDCR) [2]. Thus, T. kivui is an ideal production platform in a formate-based bioeconomy but also in biological hydrogen production and storage [3]. One missing link in formate metabolism of T. kivui was the nature of formate uptake/export.
Goals: To identify and characterize a possible formate transporter in T. kivui.
Materials & Methods: Bioinformatic analysis, generation of deletion mutants, growth experiments and cell suspension experiments.
Results: Inspection of the genome sequence revealed a gene, fdhC, adjacent to the hdcr gene cluster whose product is similar to the Escherichia coli formate transporter FocA. The gene was deleted by allelic replacement. The deletion mutant had no phenotype at pH 7.0 and 150 mM formate, conditions used to grow the wildtype. However, at high pH and low formate concentrations, formate consumption by the mutant was drastically reduced.
Summary: We identified the formate transporter of T. kivui and its role in the physiology of T. kivui is discussed.
[1] Burger Y., Schwarz F. M. and Müller V. (2022) Biotechnol Biofuels 15:48
[2] Schwarz F. M. and Müller V. (2020) Biotechnol Biofuels 13:32
[3] Müller V. (2019) Trends Biotechnol 37:1344-1354