Chemoheterotrophic organisms

Chemoheterotrophs Organic compounds Oxidation-reduction reactions Organic compounds, e.g., glucose All animals, most microorganisms, nonphotosynthetic plant tissue such as roots, photosynthetic cells in the dark... 

Where a single substrate serves both as carbon and energy source, which is the case for chemoheterotrophic organisms used for biomass production, we can write ... 

For a more detailed stoichiometric representation for aerobic growth of a chemoheterotrophic organism we must consider... 

Organisms that use CO2 as the principal carbon source are defined as autotrophic organisms that use organic compounds as the principal carbon source are defined as heterotrophic. A combination ofthese two criteria leads to the establishment of four principal categories (i) photoautotrophic, (ii) photoheterotrophic, (Hi) chemoautotrophic and (iv) chemoheterotrophic organisms. 

Fig. 1.2. A schematic presentation of the processes which yield energy and biosynthesize organic compounds in the chemoheterotrophic organisms. [CH20] in this figure and in the following figures represents the organic compounds newly biosynthesized in the organisms...

In a system defined by wastewater in a sewer network, the heterotrophic bacteria dominate the microbial community, i.e., organic compounds are required as a carbon source. Furthermore, the energy source (electron donor) for the heterotrophs is primarily also organic compounds, i.e., the heterotrophs that dominate wastewater in sewers are chemoheterotrophic (chemoorganotrophic) microorganisms. 

Heterotrophic mode heterotrophs obtain energy and carbon from organic substances. Thus, chemoheterotrophs obtain energy from oxidations, whereas photoheterotrophs obtain energy from photosynthesis with an organic electron donor requirement. 

Many chemoheterotrophic bacteria oxidize organic compounds with molecular oxygen (Fig. 1.2). They oxidize many organic compounds such as carcasses and excreta of animals, and dead plants, and participate in the cleaning pollution from the surface of Earth. 

Fermentation is one of the chemoheterotrophic energy acquiring processes. In this process, organic compounds are anaerobically oxidized by organic compounds to produce ATP (Fig. 1.5). For example, in alcohol fermentation, glyceraldehyde-... 

The prosthecate bacteria are typical aquatic organisms. The genera Caulobacter and Hyphomicrobium are aerobic chemoheterotrophs, whereas Rhodomicrobium is a photosynthetic purple bacterium. Other peculiar aquatic bacteria have been described (see, e.g., ref. [11]). 

The terms obligate and facultative are also used obligate organisms can only use that form of nutrition, whilst facultative can switch from one form to another. The most common example of facultative organisms is the algae, many of which are photo autotrophs in the light, but may be chemoheterotrophs in the dark. 

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