TABLE OF CONTENTS
1. Introduction
2. Definition of Autotrophic Bacteria
3. Types of Autotrophic Bacteria
4. Classification of Autotrophic Bacteria (Detailed)
5. Mechanisms of Autotrophic Bacteria (Detailed with diagrams)
6. Ecological Importance
7. Industrial Importance
8. Differences between Photo and Chemoautotrophs
9. Conclusion
10. References
1. Introduction
Autotrophy is a life style in which inorganic compounds provide for all nutritional needs of
an organism. Implicit in this definition is the capacity of an organism to derive all cell carbon from
carbon dioxide.
Autotrophs are capable of growth exclusively at the expense of inorganic nutrients and they
are vital in the cycling of inorganic compounds. Such autotrophs not only completely satisfied their
own needs for reduced carbon monomers from inorganic matter but could also feed the already
existing heterotrophs. Thus, autotrophic organisms are also called primary producers. Carbon
dioxide that is fixed into organic compounds as a result of autotrophic activity is available for
consumption or respiration by animals or heterotrophic microorganism. The end products of
respiration in heterotrophic organism are carbon dioxide and this way the carbon cycle is
completed. Now it is accepted that autotrophy is an extremely important process on Earth and
autotrophic microorganisms, as primary producers, support the growth of non-autotrophic
organisms.
Few bacteria possess photosynthetic pigment bacteriochlorophyll other than normal
chlorophyll found in higher plants are called photosynthetic bacteria. Thus, autotrophic bacteria are
of two types based on the energy sources: (1) Photoautotrophs (Photosynthetic bacteria) are
photosynthetic and obtain energy from sunlight. (2) Chemoautotrophs (Chemosynthetic bacteria)
obtain energy by the oxidation of other substances.
1
,2.0 DEFINITION OF AUTOTROPHIC BACTERIA
WHAT IS AN AUTOTROPHIC BACTERIA?
Autotrophic bacteria are those bacteria that can synthesize their own food. They perform several
reactions involving light energy (photons) and chemicals in order to derive energy for their
biological sustainability. In order to do so, they utilize inorganic compounds like carbon dioxide,
water, hydrogen sulfide, etc. for converting them into organic compounds like carbohydrates,
proteins, etc. which are known to be energy-providing molecules in biological systems. Thus,
autotrophic bacteria are self-sustaining organisms much similar to plants in terms of nutritional
dependency.
2.1 DIAGRAM OF AN AUTOTROPHIC BACTERIA
2
, 3.0 TYPES OF AUTOTROPHIC BACTERIA
3.1 Photoautotrophs bacteria
A large number of bacteria, as well as the green plants and algae, are photoautotrophs. They
use light as energy source and CO2 as unique source of carbon to synthesize carbohydrate in the
process called photosynthesis. The result of this mechanism is the generation of a proton motive
force (PMF) that can be used in the synthesis of ATP and the synthesis of reducing power (e.g.,
NADPH).
The photosynthetic bacteria possess a special type of pigment called bacteriochlorophyll.
Along with this other pigment viz. Bacteriviridin (type of bacteriochlorophyll) or chlorobium
chlorophyll (green sulfur bacteria) is also found. These pigments are found on spiral structures
called chromatophores. Generally, the CO2 fixation process occur in the presence of sulphur
compounds which is mainly H2S (hydrogen sulphide) (anoxygenic photosynthetic bacteria).
Therefore, it can be said that hydrogen sulphide is main hydrogen source in photosynthesis in
bacteria and here sulphur is produced as byproduct in place of oxygen (produced in higher plants
and oxygenic photosynthetic bacteria, Cyanobacteria) in the chemical reaction.
The chemical reaction of photosynthesis is as follows
CO2 + H2S → (CH2O)n + 2S + H2O + energy
e.g. Chromatium, Chlorobium and Chlorobacterium (anoxygenic photosynthetic bacteria).
6CO2 + 6H2O → C6H12O6 + 6O2
e.g. Cyanobacteria (oxygenic photosynthetic bacteria)
3.2 Chemoautotrophs
Many bacteria, called chemosynthetic bacteria, uses the energy released from different type
of chemical reactions for the conversion of carbon dioxide into carbohydrate (because they cannot
3
1. Introduction
2. Definition of Autotrophic Bacteria
3. Types of Autotrophic Bacteria
4. Classification of Autotrophic Bacteria (Detailed)
5. Mechanisms of Autotrophic Bacteria (Detailed with diagrams)
6. Ecological Importance
7. Industrial Importance
8. Differences between Photo and Chemoautotrophs
9. Conclusion
10. References
1. Introduction
Autotrophy is a life style in which inorganic compounds provide for all nutritional needs of
an organism. Implicit in this definition is the capacity of an organism to derive all cell carbon from
carbon dioxide.
Autotrophs are capable of growth exclusively at the expense of inorganic nutrients and they
are vital in the cycling of inorganic compounds. Such autotrophs not only completely satisfied their
own needs for reduced carbon monomers from inorganic matter but could also feed the already
existing heterotrophs. Thus, autotrophic organisms are also called primary producers. Carbon
dioxide that is fixed into organic compounds as a result of autotrophic activity is available for
consumption or respiration by animals or heterotrophic microorganism. The end products of
respiration in heterotrophic organism are carbon dioxide and this way the carbon cycle is
completed. Now it is accepted that autotrophy is an extremely important process on Earth and
autotrophic microorganisms, as primary producers, support the growth of non-autotrophic
organisms.
Few bacteria possess photosynthetic pigment bacteriochlorophyll other than normal
chlorophyll found in higher plants are called photosynthetic bacteria. Thus, autotrophic bacteria are
of two types based on the energy sources: (1) Photoautotrophs (Photosynthetic bacteria) are
photosynthetic and obtain energy from sunlight. (2) Chemoautotrophs (Chemosynthetic bacteria)
obtain energy by the oxidation of other substances.
1
,2.0 DEFINITION OF AUTOTROPHIC BACTERIA
WHAT IS AN AUTOTROPHIC BACTERIA?
Autotrophic bacteria are those bacteria that can synthesize their own food. They perform several
reactions involving light energy (photons) and chemicals in order to derive energy for their
biological sustainability. In order to do so, they utilize inorganic compounds like carbon dioxide,
water, hydrogen sulfide, etc. for converting them into organic compounds like carbohydrates,
proteins, etc. which are known to be energy-providing molecules in biological systems. Thus,
autotrophic bacteria are self-sustaining organisms much similar to plants in terms of nutritional
dependency.
2.1 DIAGRAM OF AN AUTOTROPHIC BACTERIA
2
, 3.0 TYPES OF AUTOTROPHIC BACTERIA
3.1 Photoautotrophs bacteria
A large number of bacteria, as well as the green plants and algae, are photoautotrophs. They
use light as energy source and CO2 as unique source of carbon to synthesize carbohydrate in the
process called photosynthesis. The result of this mechanism is the generation of a proton motive
force (PMF) that can be used in the synthesis of ATP and the synthesis of reducing power (e.g.,
NADPH).
The photosynthetic bacteria possess a special type of pigment called bacteriochlorophyll.
Along with this other pigment viz. Bacteriviridin (type of bacteriochlorophyll) or chlorobium
chlorophyll (green sulfur bacteria) is also found. These pigments are found on spiral structures
called chromatophores. Generally, the CO2 fixation process occur in the presence of sulphur
compounds which is mainly H2S (hydrogen sulphide) (anoxygenic photosynthetic bacteria).
Therefore, it can be said that hydrogen sulphide is main hydrogen source in photosynthesis in
bacteria and here sulphur is produced as byproduct in place of oxygen (produced in higher plants
and oxygenic photosynthetic bacteria, Cyanobacteria) in the chemical reaction.
The chemical reaction of photosynthesis is as follows
CO2 + H2S → (CH2O)n + 2S + H2O + energy
e.g. Chromatium, Chlorobium and Chlorobacterium (anoxygenic photosynthetic bacteria).
6CO2 + 6H2O → C6H12O6 + 6O2
e.g. Cyanobacteria (oxygenic photosynthetic bacteria)
3.2 Chemoautotrophs
Many bacteria, called chemosynthetic bacteria, uses the energy released from different type
of chemical reactions for the conversion of carbon dioxide into carbohydrate (because they cannot
3
