Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction to bacterial physiology and metabolism
- 2 Composition and structure of prokaryotic cells
- 3 Membrane transport – nutrient uptake and protein excretion
- 4 Glycolysis
- 5 Tricarboxylic acid (TCA) cycle, electron transport and oxidative phosphorylation
- 6 Biosynthesis and microbial growth
- 7 Heterotrophic metabolism on substrates other than glucose
- 8 Anaerobic fermentation
- 9 Anaerobic respiration
- 10 Chemolithotrophy
- 11 Photosynthesis
- 12 Metabolic regulation
- 13 Energy, environment and microbial survival
- Index
- References
10 - Chemolithotrophy
Published online by Cambridge University Press: 05 September 2012
- Frontmatter
- Contents
- Preface
- 1 Introduction to bacterial physiology and metabolism
- 2 Composition and structure of prokaryotic cells
- 3 Membrane transport – nutrient uptake and protein excretion
- 4 Glycolysis
- 5 Tricarboxylic acid (TCA) cycle, electron transport and oxidative phosphorylation
- 6 Biosynthesis and microbial growth
- 7 Heterotrophic metabolism on substrates other than glucose
- 8 Anaerobic fermentation
- 9 Anaerobic respiration
- 10 Chemolithotrophy
- 11 Photosynthesis
- 12 Metabolic regulation
- 13 Energy, environment and microbial survival
- Index
- References
Summary
Some prokaryotes grow by using reduced inorganic compounds as their energy source and CO2 as the carbon source. These are called chemolithotrophs. The electron donors used by chemolithotrophs include nitrogen and sulfur compounds, Fe(II), H2, and CO. The Calvin cycle is the most common CO2 fixation mechanism, and the reductive TCA cycle, acetyl-CoA pathway and 3-hydroxypropionate cycle are found in some chemolithotrophic prokaryotes. Some can use organic compounds as their carbon source while metabolizing an inorganic electron donor. This kind of bacterial metabolism is referred to as mixotrophy.
Reverse electron transport
As with chemoorganotrophs, metabolism of chemolithotrophs requires ATP and NAD(P)H for carbon metabolism and biosynthetic processes. Some of the electron donors used by chemolithotrophs have a redox potential higher than that of NAD(P)+/NAD(P)H (Table 10.1). Electrons from these electron donors are transferred to coenzyme Q or to cytochromes. Some of the electrons are used to generate a proton motive force reducing O2 while the remaining electrons reduce NAD(P)+ to NAD(P)H through a reverse of the electron transport chain. The latter is an uphill reaction and coupled with the consumption of the proton motive force (Figure 10.1). This is referred to as reverse electron transport. In most cases, electron donors with a redox potential lower than NAD(P)+/NAD(P)H are oxidized and this is coupled with the reduction of coenzyme Q or cytochromes for the efficient utilization of the electron donors at low concentration.
- Type
- Chapter
- Information
- Bacterial Physiology and Metabolism , pp. 354 - 385Publisher: Cambridge University PressPrint publication year: 2008