All details about the bacterial metabolism oxidation, fermentation, oxidation reduction potential

1. BACTERIAL METABOLISM
INTRODUCTION:-
The series of changes of substance (carbohydrate, protein or fat) within the bacterial cell from absorption to
elimination is known as metabolism of the substance.
Aerobic bacteria obtain their energy only through oxidation involving oxygen as the ultimate hydrogen
acceptors,
while the anaerobes use hydrogen acceptors other than oxygen
A. Oxidation
 The conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) provides
energy in this process. This process is called oxidative phosphorylation.
 Small amount of hydrogen peroxide produced in the process is disposed off by enzymes catalase
or peroxidase present in aerobes.
B. Fermentation
 In anaerobic respiration, hydrogen acceptor compounds are nitrates or sulphates, instead of
oxygen.
 In fermentation, a series of oxidoreductions occur in which the carbon and energy source acts as
both the electrondonor and electron acceptor.
 During fermentation, energy rich phosphate bonds are produced by the introduction of organic
phosphate into intermediate metabolite.
 This process is known as substrate-level phosphorylation .
 These energy-rich phosphate groups so formed help in conversion of ADP to ATP.
 Fermentation is carried out by both obligate and facultative anaerobes.
Clinical Significance
Biochemical reactions are used for identification of Gram negative bacilli.
Carbohydrates are fermented to produce acid (lactic acid, pyruvic acid etc.) and gas (hydrogen, carbon
dioxide).
C. Oxidation-Reduction (O-R) Potential (Redox potential)
 Oxidising agent is a substance which can accept electrons while reducing agent is able to part
with electrons.
 The oxidising or reducing condition of a system is indicated by the net readiness of all the
components in that system to accept or to part with the electrons.
 This is called oxidation-reduction potential or redox potential.

2.  The redox-potential of the medium can also be assessed by the use of certain indicator dyes such
as methylene blue or resazurin, which become coloured in oxidised state.
Clinical Significance:-
Anaerobic jar is used for growing anaerobic bacteria in it.
Methylene blue solution is colourless in anaerobic conditions and blue in aerobic conditions.
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DHANANJAYSINGH