Bacterial Energy Source

Bacterial Energy Source

	Bacterial Energy Source - The conventional definition of autotrophs includes the concept that the organisms obtain energy from the oxidation of reduced inorganic chemicals. Whitten bury and Kelly, however, point out that autotrophs do not have any common mechanism of inorganic chemical oxidation.
The different substrates like NO2-,NH4 +reduced sulphur compounds, H+ and Fe++ are oxidized by different enzyme complexes and pathways. Moreover certain organisms considered to be heterotrophs also oxidize inorganic substances. Thus Desulfovibrio and Desulfotomaculum species oxidize hydrogen, and various pseudomonads oxidize thiosulphate to tetrathionate. Oxidative reduction of inorganic compounds is thus not confined to autotrophs, and is not the distinguishing feature of autotrophs.
According to the broadened view of autotrophy proposed by Whittenbury and Kelly: (i) All microorganisms primarily dependent on C1 compounds as sources of carbon are autotrophs, irrespective of whether they are obligate or facultative. (ii) Carbon fixation pathways can either be the ribulose diphosphate pathway, or the ribulose monophosphate pathway, or the serine pathway.
(iii) The inorganic or organic nature of the energy sources are not distinguishing features for defining autotrophs. Very few species of bacteria are autotrophs. According to the commonly accepted usage autotrophs are divided into two groups chemolithoautotrophs and photolithoautotrophs. These two groups are often referred to chemolithotrophs and, photolithotrophs, respectively.
	These terms, however, refer only to an ability to use inorganic compounds as sources of energy or electrons. This property also belongs to some heterotrophs which have an obligatory requirement of organic compounds as major sources of carbon.

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Phototrophs Chlorobiaceae - Chlorobacteriacae Green S Bacteria Chloroflexaceae - Green Filamentous Bacteria Chromatiaceae - Thiohodaceae - Purple S Bacteria Rhodospirillaceae - Athiorhodaccae - Purple non-S Bacteria Cyanobacteria - Bule Green Algae - Blue Green Bacteria Prochlorophyta Chemotrophs Obligate Chemolithotrophs Facultative Chemolithotrophs Methanogenesis

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