Chemolithotrophy

Nutritional types in bacteria: Chemolithotrophy.

1. Microbial Physiology and Metabolism Chemolithotrophy Presentation by: DEEPALI SEEMA YADAV

2. Basic needs of a cell : Carbon source Source of energy Source of electrons

3. Introduction to Chemolithotrophs Organisms that obtain energy from the oxidation of inorganic (or organic) compounds are called chemolithotrophs . They are also be called chemolithoautotrophs .

4. Discovery of Chemolithotrophy First elaborated by Sergei Winogradsky . Studied sulphur bacteria ( Beggiatoa , Thiothrix ). Observations 1. sulphur bacteria were only present in water containing H2S. 2. when water flowed away, sulphur bacteria disappeared. 3. sulphur granules were present in their filaments. 4. granules lost when bacteria starved for H2S and sulphate appeared in medium. Conclusion : H2S S (SO4)2-

5. Sources of Inorganic Electron Donor Inorganic Electron Donor Geological Anthropogenic Biological Volcanic activity (H2S) Mining , burning fossil fuels (CO,H2) Agriculture (H2S, H2, NH3)

6. CO2 fixation By Calvin cycle Requirements: 1. Energy (ATP) -3 2. Reducing power (NADH or reduced ferredoxin )-2

7. Energetics in Chemolithotrophy ATP (energy) NADH (reducing power)

8. Problems faced:- Less energy availability from oxidation of inorganic compounds than that of organics. Electron flow from more negative to positive reduction potential. More negative reduction potential of NADH (than NH3 and NO2-).

9. Solutions: Oxidation of more substrate. Reverse electron flow.

10. Types of Chemolithotrophs Aerobic Terminal electron acceptor is oxygen in ETC. Example: hydrogen-oxidising bacteria, iron bacteria. Anaerobic Terminal electron acceptor in ETC is not O2 but any other compound. Example: Methanogenic bacteria, Sulfidogenic bacteria.