Microorganisms, autotrophic

Carbon dioxide is produced as a result of metabolism of all heterotrophic organisms. The concentrations of CO2 in pore water of reduced sediments are therefore high. Autotrophic microorganisms consume CO2 in the oxidized part of the sediment, which can vary in depth from a meter in deep sea sediments to a few mm... 

Microorganisms at aqueous-solid phase interfaces have different respiration modes which include (a) aerobic heterotrophic, (b) aerobic autotrophic, (c) facultative anaerobic heterotrophic, (d) facultative anaerobic autotrophic, and (e) anaerobic heterotrophic respiration modes [36,41,43,47, 55]. Table 3 shows the main differences between these different respiration modes. 

Aeration and odour control by heterotrophic and autotrophic microorganisms... 

The requirement for vitamins in humans and other animals is the result of mutations in the enzymes involved in biosynthetic coenzymes. As intermediates of coenzyme biosynthesis are available in suf cient amounts in the diet of heterotrophic animals (see p. 112), the lack of endogenous synthesis did not have unfavorable effects for them. Microorganisms and plants whose nutrition is mainly autotrophic have to produce all of these compounds themselves in order to survive. 

Figure 10.12. A. Carbon isotopic composition of major groups of higher plants and autotrophic microorganisms compared with oxidized carbon (CO2, HCO3, CC>32 )- The triangles are mean values. (After Holser et al 1988 Schidlowski, 1988). B. Sulfur isotopic composition of bacteriogenic sulfide in modern marine anaerobic sediments (open bars, 1-6) and in the Permian Kupferschiefer (black bar, 7) compared with oxidized sulfate of modem (1-6) and Permian seawater (+11 %o). The black triangles are mean values. (After Holser et al., 1988.)...

Some microorganisms can catalyze certain oxido-reduction reactions like the oxidation of iron and manganese in water, the oxidation of sulfur compounds, and oxidation-reduction of nitrogen compounds. Aerobic autotrophic bacteria of the type Thiobacillus can release soluble iron, copper, and sulfuric acid as sulphates into water. These organisms can be found everywhere in nature wherever an acidic environment is maintained in the presence of sulfide-containing minerals. 

The carbon required by living organisms is an important constituent of cellular structure and metabolic compounds. This element is present in the environment in many forms. It may appear in simple form as gaseous carbon dioxide or as more complex organic compounds. Microorganisms are remarkably diverse in their carbon requirements and they are divided into two groups autotrophs and heterotrophs, based on their carbon source. 

Autotrophic microorganisms synthesize organic substances from carbon dioxide through a process known as carbon dioxide fixation. They are important in nature because carbon dioxide fixation works as a precursor for the organic substrates that form the basis of the food chain for other organisms. Autotrophic bacteria include those that obtain their energy from light (photoautotrophs) and those that obtain it from the oxidation of chemical bonds (chemoau-totrophs). 

Autotrophs— Microorganisms that utilize inorganics for energy. 

Classical coupled nitrification-denitrification requires NH, organic carbon, aerobic conditions, and anaerobic conditions. It involves three distinct populations of microorganisms, some of which are heterotrophic and others autotrophic. As a result, regulation of the process is rather complex and the relative proportions of NOj", NO, N2O, and N2 as end products varies widely with environmental and ecological conditions. 

---