Mixotrophic Growth of Thiobacillus A2 in Chemostat Culture on Formate and Glucose

Abstract

In aerobic chemostat culture Thiobacillus A2-GFI grew autotrophically on formate and heterotrophically on glucose with maximum specific growth rates (,urn,,) of 0.21 and 0.33 h-l, respectively. At dilution rates of 0.1 and 0.18 h-l, it grew mixotrophically on formate + glucose mixtures, completely consuming both substrates. Ribulose-1,5-bisphosphate carboxylase and formate dehydrogenase were present at high specific activity in autotrophic and mixotrophic cultures, but were repressed in cultures on glucose alone. A greater proportion of added glucose was assimilated in mixotrophic culture than in heterotrophic culture. Raising the dilution rate of a mixotrophic culture from 0.1 or 0.18 to 0.3 h-' resulted in washout (with an apparent p,,, for mixotrophic growth of 0.25 h-l) and the establishment of a culture dependent on glucose for growth. Growth yields on formate and glucose were, respectively, 3 -3 and 100 g dry wt (mol substrate consumed)-'. Steady state biomass production in mixotrophic culture indicated additive growth yields. The biomass produced in cultures on formate + glucose at a dilution rate of 0-3 h-l suggested that growth only occurred on glucose, but organisms still contained high activities of ribulose-1,5-bisphosphate carboxylase and formate dehydrogenase. At a formate :glucose ratio (mM) of 100 : 1, some formate was oxidized and CO, was fixed, but formate was not used when this ratio was 5 0 : 5 . Formate-glucose mixotrophy benefits Thiobacillus A2-GFI when substrates are limited at low growth rates (<,urnax for formate), but is characterized by a pmax below that possible on glucose. Physiological behaviour at high growth rates was influenced by the formate :glucose ratio, resulting under some conditions, at least, in loss of mixotrophy and the establishment of heterotrophic growth.

Purification and Characterization of an α-Haloketone-resistant Formate Dehydrogenase fromThiobacillussp. Strain KNK65MA, and Cloning of the Gene

“…The strain expressed 0.41 units of FDH activity per ml of the culture broth, and was identied as Thiobacillus sp., the FDH of which has been reported previously. [35][36][37][38][39] Puriˆcation and properties of FDH The FDH was puriˆed about 26-fold ( Table 2). The puriˆed enzyme was a single protein band of 44 kDa on SDS-PAGE.…”

Two modes of sulfite oxidation in the extremely thermophilic and acidophilic archaeon Acidianus ambivalens

“…In addition, the APAT activity was measured in an assay similar to the one described above for adenylate kinase except that 1 mM APS and 1 mM K 2 HPO 4 were added instead of AMP and ATP. Rhodanese activity was measured either by the thiosulfate-and cyanide-dependent reduction of dichloroindophenol at 75°C (Kelly and Wood 1994) or by colorimetric determination of the product SCN - (Wood and Kelly 1981).…”

Reidentification of Thiobacillus perometabolis ATCC 27793 and Thiobacillus sp. Strain A2 with Reference to a New Species, Thiobacillus rapidicrescens sp. nov.

“…strain A2T (type strain) has been investigated mainly with respect to its facultatively chemolithotrophic characteristics (2,7,12,18); however, this strain has not been correctly identified since the isolation of the organism was reported by Taylor and Hoare in 1969 (14). In the course of our taxonomic studies on Thiobacillus species, we found that there is a close relationship between Thiobacillus sp.…”