Energy-Yielding Metabolism in Bacteria

Section: Discussionmentioning

confidence: 67%

End-products, Fermentation Balances and Molar Growth Yields of Homofermentative Lactobacilli

Dirar

Collins²

1972

“…However, we found that the total polysaccharide content of Propionibacterium freudenreichii was the same after anaerobic and aerobic growth, namely I I %, the normal percentage for the cell wall polysaccharides (Gunsalus & Shuster, 1961). Therefore, the lowered cytochrome content of aerobic cells must indeed be ascribed to inhibition of cytochrome synthesis by oxygen.…”

Section: V a N Wijck-kapteijn A N D A H S T O U T H A M E Rmentioning

confidence: 71%

Influence of Oxygen on Growth, Cytochrome Synthesis and Fermentation Pattern in Propionic Acid Bacteria

Vries

Wijck-Kapteijn

Stouthamer

1972

SUMMARYThe influence of oxygen on growth and cytochrome synthesis was investigated in four species of Propionibacterium. After anaerobic growth all species contained cytochrome b, cytochrome a or a,, cytochrome a, and a carbon monoxide-binding pigment. Cytochrome b functions in an electron transport system from lactate to fumarate since the lactate-fumarate dismutation reaction, unlike lactate oxidation via methylene blue, was strongly inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO). No species grew on agar plates under aerobic conditions but all grew in aerated media, though at different rates and with diminished synthesis of all cytochromes. In Propionibacterium freudenreichii and P.shermanii, which grew slower under aerobic conditions than P. rubrum and P.pentosaceum, cytochrome synthesis was more repressed by oxygen. Large amounts of pyruvate accumulated under aerobic conditions whereas acetate, propionate and succinate were not formed. The bacteria are therefore dependent on oxidative phosphorylation for energy under aerobic conditions. For P. freudenreichii an Yo value (g dry wt bacteria/g-atom oxygen taken up) of 15 was measured, suggesting a P/O value of I to 2. Absence of cytochrome synthesis resulting in the loss of oxidative phosphorylation may explain the absence of aerobic growth on agar plates.

“…Growth yields on hexoses were very high (up to 82 g dry wt bacteria/mol glucose). The total polysaccharide content of P. freudenreichii varied from 12 to 140& the normal percentage for cell wall polysaccharides (Gunsalus & Shuster, 1961). Thus, the high molar growth yields were not due to formation of storage products.…”

Section: W D E V R I E S and O T H E R Smentioning

confidence: 91%

Generation of ATP during Cytochrome-linked Anaerobic Electron Transport in Propionic Acid Bacteria

Vries

Wyck-Kapteyn

Stouthamer

1973

S U M M A R YEnzyme determinations in bacteria-free extracts and dual-wavelength experiments with membrane suspensions established that Propionibacteriunz freudenreichii converted glycerol into triose phosphate via glycerol kinase and NAD-independent glycerol I -phosphate dehydrogenase which is closely linked to cytochrome b. Glycerol I-phosphate dehydrogenase uses fumarate as a final hydrogen acceptor. The enzyme system catalysing fumarate reduction with glycerol I-phosphate as a hydrogen donor, is membrane bound and is strongly inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO). Fumarate reduction with reduced benzyl-viologen is not inhibited by HOQNO. Cytochrome b is therefore probably involved in the anaerobic electron transport from glycerol I -phosphate to fumarate. Molar growth yields and fermentation balances were determined for P. freudenreichii and P. pentosaceuin growing on glucose, fructose, glycerol and lactate and ATP yields (mol of ATP formed/mol of substrate fermented) were calculated assuming that I mol ATP is formed in the electron transport from glycerol I-phosphate and lactate to fumarate, and that 2 rnol ATP are formed in the electron transport from NADH to fumarate. Mean YaTp values (g dry wt bacteria/mol ATP) were 15-2 and 12-9 for P. freudenreichii, and 16.4 and I 1.8 for P. pentosaceurn each growing on complex or synthetic medium respectively. The observation that for each strain YATP values were constant for the same medium, supported our assumptions on energy generation in propionic acid bacteria.