thermocellum ATCC 27405 Cthe_0143   Cthe_1253 Cthe_2874 Cthe_0699-0701 Cthe_0345 Cthe_0344       Cthe_1308         C. thermocellum DSM 4150     CtherDRAFT_1661 CtherDRAFT_1742 CtherDRAFT_0819-0822 YesA YesA       CtherDRAFT_1896         Ta. pseudethanolicus 39E Teth39_0735 Teth39_0684 Teth39_1358 Teth39_0711     Teth39_0337       Teth39_2098         G. thermoglucosidasius C56-YS93 Geoth_0446 Geoth_0898   Geoth_0811   Geoth_0904

Geoth_1713             Geoth_3508 Geoth_2444 B.cereus ATCC 14579 BC5135 BC3323 BC3087 BC4762   BC4592 BC0580 NAD)     BC4599       BC2959 BC1741 (NAD)               BC4604 (NADP) AGenes have been verified by PCR amplification (unpublished). Abbreviations: eno, enolase; ppk, pyruvate kinase; ppdk, pyruvate phosphate dikinase; pepck, phosphoenolpyruvate carboxykinase; oaadc, oxaloacetate decarboxylase; mdh, malate dehydrogenase; malE, malic enzyme. Flux balance analysis integrated Tariquidar purchase with RNAseq data suggests higher carbon

and electron flux in C. thermocellum ATCC 27405 is directed through enzymes capable of direct, rather than indirect, conversion of PEP to pyruvate [77]. However, C. cellulolyticum mutation studies suggests that a portion of PEP can also be converted to pyruvate via the “malate shunt” [78]. This PPK/PPDK bypass system utilizes either (i) phosphoenolpyruvate carboxykinase (PEPCK), malate SC79 in vivo dehydrogenase (MDH), and malic enzyme (MalE), or (ii) PEPCK and oxaloacetate decarboxylase (OAADC), for the interconversion of PEP and pyruvate this website (Figure 1). While PEPCK provides a pathway for energy conservation via ATP (or GTP) production, MDH and MalE permit transhydrogenation

from NADH to NADP+[71], 17-DMAG (Alvespimycin) HCl generating additional reducing equivalents required for biosynthesis. G. thermoglucosidasius, B. cereus, C. thermocellum (ATCC 27405), and C. cellulolyticum contain pepck, mdh and malE suggesting that they are capable of transhydrogenation using these proteins. Although the draft genome of C. thermocellum DSM 4150 does not include genes encoding MDH and MalE, we have verified their presence via PCR amplification (unpublished results). Deletion of mdh in C. cellulolyticum resulted in significant increases in lactate, and to a lesser extent ethanol yields, and reduced acetate production when grown on cellulose demonstrating carbon and electron flux through MDH in wild type strains [78]. It seems evident that in the absence of MDH, transhydrogenation was reduced, and thus the resulting increase in NADH:NADPH ratios promote lactate and ethanol production, while decreasing NADPH levels for biosynthesis. A number of organisms analyzed encode pepck and oaadc (Ca. bescii, Ca. saccharolyticus, C. cellulolyticum, C. phytofermentans, and C. thermocellum), also allowing for indirect conversion of PEP to pyruvate via an oxaloacetate intermediate.