Pictorial representation of reductive citric acid cycle for autotrophic CO2 fixation. The enzyme catalyzed reactions are shown by arrows. Enzyme activities: 1, malate dehydrogenase (EC 1.1.1.37); 2, fumarate hydratase (fumarase) (EC 4.2.1.2); 3, fumarate reductase; 4, succinyl-CoA synthetase (EC 6.2.1.5); 5, 2-oxoglutarate:ferredoxin oxidoreductase (EC 1.2.7.3); 6, isocitrate dehydrogenase (EC 1.1.1.42); 7, aconitate hydratase (aconitase) (EC 4.2.1.3); 8, ATP citrate lyase (EC 2.3.3.8); and 9, pyruvate: ferredoxin oxidoreductase (EC 1.2.7.1). Fdred, reduced ferredoxin. The enzymes observed in the genome of tuberculosis strains were highlighted with red color.