This document discusses chemolithotrophs, which are organisms that obtain energy from oxidizing inorganic or organic compounds. It notes that chemolithotrophs, also called chemolithoautotrophs, were first studied by Sergei Winogradsky in sulfur bacteria. Chemolithotrophs face challenges due to the lower energy availability from oxidizing inorganic compounds compared to organics, and solutions include oxidizing more substrate and using reverse electron flow. The document categorizes chemolithotrophs as aerobic, using oxygen as the terminal electron acceptor, or anaerobic, using other compounds besides oxygen.

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

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

6. 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-

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

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

12. Energetics in
Chemolithotrophy
• ATP (energy)
• NADH (reducing power)

14. 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-).

17. Solutions:
• Oxidation of more substrate.
• Reverse electron flow.

19. 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.