Table 1.
Specific enzyme activities (U per mg protein) in Pelobacter species. If not mentioned otherwise, all enzyme assays were done with the P. carbinolicus/M. hungatei strain M1h coculture. (DCPIP = 2,6-dichlorophenolindophenol, n. ac. = non-acetylating, BV = benzyl viologen, MV = methyl viologen, M. arb. = Methanobrevibacter arboriphilus, n. d. = not determined).
Table 2.
Specific enzyme activities (U per mg protein) in cytoplasmic fractions of Pelobacter carbinolicus cultivated with and without molybdate and tungstate. (n. ac. = non-acetylating, BV = benzyl viologen, MV = methyl viologen).
Figure 1.
Electrophoretic separation of soluble proteins (20 µg) of P. carbinolicus grown in media containing 20 mM ethanol and either 300 nM tungstate without molybdate (W) or 150 nM molybdate without tungstate (Mo).
Marked bands were identified as a Mo-dependent acetaldehyde dehydrogenase (A, Pcar_0220) and W-dependent acetaldehyde dehydrogenase isoforms (B, Pcar_0665/0456) by peptide mass fingerprinting.
Figure 2.
Two-dimensional PAGE comparison of soluble proteins of P. carbinolicus grown on 20 mM ethanol in tungstate-free or tungstate-rich medium to identify differentially induced (red or blue) or constitutively (green) expressed proteins by peptide mass fingerprinting.
Spots are labeled by locus tag of the identified protein: Pcar_0833/0835 = formate dehydrogenase, Pcar_1633/1634 = hydrogenase, Pcar_1501 = glutamine synthetase, Pcar_1246/2758 = acetylating acetaldehyde dehydrogenase, Pcar_0251/0255 = alcohol dehydrogenase isoforms.
Figure 3.
Cultivation of Pelobacter carbinolicus either in pure culture or in coculture with Methanospirillum hungatei strain M1h on acetaldehyde, ethanol or acetoin.
Curves depict concentrations (mM) of acetoin (diamonds), ethanol (squares), acetate (triangles), hydrogen (open squares), formate (open triangles) and the optical density (OD, circles) under different growth conditions. In coculture experiments with ethanol (B) or acetoin (D), the methanogenic partner was inhibited by addition of 4 mM bromoethanesulfonate (BES), and ethanol oxidation was restarted with about 20 mM ethanol (see arrow) after regular growth was finished. Growth and metabolic performance of P. carbinolicus was similar to growth of P. acetylenicus on acetaldehyde (A) or ethanol (B) as shown in S4 Fig. Concentrations were measured in triplicate.