Carbohydrate Degradation Pathways in Thiobacillus A2 Grown on Various Sugars

Abstract

A detailed radiorespirometric and enzymological analysis was made of the wild-type and GFI strains of Thiobacillus A2 grown on numerous sugars. The wild-type used the EmbdenMeyerhof, Entner-Doudoroff and pentose phosphate pathways for glucose oxidation only after culture on glucose. The fast-growing strain GFI used all three pathways after growth on glucose, maltose or fructose. The wild-type grown on a wide range of pentoses, hexoses, disaccharides, a trisaccharide and a mixture of glucose and maltose oxidized glucose by means of the Entner-Doudoroff pathway (68 to 90%) and pentose phosphate pathway (10 to 32 yo). The key enzyme determining the presence or absence of the Embden-Meyerhof pathway was 6-phosphofructokinase. Other mechanisms, such as a phosphoketolase pathway, were shown to be unimportant, even during growth on pentoses. Arabinose was metabolized via hexose phosphate synthesis. The mechanisms of regulation of sugar metabolism and the energetic significance of alternative pathways are discussed.

Experimental Identification and Quantification of Glucose Metabolism in Seven Bacterial Species

“…the main carbon-degrading pathways indicated the presence of the EMP, ED, and PP pathways (49)(50)(51). Consistent with the reported adaptation to growth solely on glucose, the specific rate of growth increased from 0.29 to 0.70 h Ϫ1 (Table 1).…”

“…Although the ED pathway is widely distributed (6,26) and is probably the oldest catabolic pathway (37), its predominance was unexpected for species capable of all three routes of glucose catabolism, such as Paracoccus versutus (49) and R. sphaeroides (5). The generally held view that the EMP pathway is the major route of glucose catabolism may thus be a misconception, because most quantitative metabolic studies were done with the model microbes E. coli, B. subtilis, C. glutamicum, and S. cerevisiae, which exhibit unusually high glycolytic fluxes.…”

“…As a member of the genus Paracoccus, Paracoccus versutus (synonyms, Thiobacillus versutus and Paracoccus strain A2) belongs to the group of ␣-proteobacteria and is closely related to the Rhodobacteraceae and distantly to pseudomonads (2). As a facultative autotroph, Paracoccus versutus is capable of heterotrophic growth on a wide rage of organic substrates that include mono-, di-, and trisaccharides (49). Extensive radiorespirometric and enzymatic analyses of FIG.…”

Autotrophic, mixotrophic and heterotrophic growth with denitrification by Thiobacillus A2 under anaerobic conditions

“…N20 (Medical Grade) and 5% (v/v) CO 2 in N~ were from The British Oxygen Company Ltd. Sources of specifically labelled glucoses were as described previously [4]. N20 (Medical Grade) and 5% (v/v) CO 2 in N~ were from The British Oxygen Company Ltd. Sources of specifically labelled glucoses were as described previously [4].…”

“…Thiobacillus A2 is capable of aerobic autotrophic growth on formate or thiosulphate, heterotrophic growth on numerous organic compounds including glucose, and mixotrophic growth on glucose with either formate or thiosulphate [1][2][3][4][5]. It is also capable of anaerobic growth on glucose and organic acids using nitrate for respiration [3,6], but is reportedly unable to grow anaerobically on thiosulphate [3].…”