Bacteria require a variety of nutrients including carbon, nitrogen, oxygen, sulfur, phosphorus, metal ions, vitamins, and water. They obtain these nutrients through different modes of nutrition. Autotrophic bacteria can synthesize their own nutrients from inorganic sources using photosynthesis or chemosynthesis. Heterotrophic bacteria rely on organic compounds from other organisms. Heterotrophs include saprophytes that decompose dead matter, parasites that live in or on other organisms, and symbionts that have mutualistic relationships.
3. INTRODUCTION
• Bacteria need energy and nutrients to complete various activities
like growth, reproduction, and metabolism.
• Bacteria exhibit wide differences with respect to the physical
condition favoring their growth, such as temperature, pH, and
gaseous environment.
4. NUTRITIONAL REQUIREMENTS:
• All organisms require a source of energy. Some rely on chemical
compounds and designated as chemotrophs. Others utilize light
energy and are called phototrophs.
• All organisms require a source of electrons for their metabolism.
Some organisms can use reduced inorganic compounds as electron
donors and termed as lithotrophs. Others use organic compounds as
electron donors and called organotrophs.
• All organisms require carbon for use in the synthesis of cell
components. Some use CO2 as major source of carbon, such
organisms are called autotrophs. Others require organic compounds
as their carbon source and are termed heterotrophs.
5. NUTRITIONAL REQUIREMENTS:
• All organisms require nitrogen for cell components. Some bacteria can
use atmospheric nitrogen while others use inorganic nitrogen compounds
such as nitrates, nitrites, or ammonium salts.
• All require oxygen, sulfur and phosphorous for cell components. Oxygen
is provided in various forms, such as water, component atoms of various
nutrients and molecular oxygen. Sulfur is required for synthesis of certain
amino acids, some bacteria require organic sulfur compounds, and some
are capable of utilizing inorganic sulfur compounds. Phosphorous in the
form of phosphate, is an essential component of nucleotides, nucleic
acids, phospholipids, teichoic acids, and other compounds.
• All living organisms require metal ions which includes Mg+, Zn2+ , K+, Ca2+
etc. These are also required for the bacterial growth.
6. NUTRITIONAL REQUIREMENTS:
• All living organisms contains vitamins and vitamin like
compounds. These function either as coenzymes for several
enzymes or as the building blocks for coenzymes.
• All living organisms require water, and in case of bacteria all
nutrients must be in aqueous solution before they can
enter the cell. Water is highly polar compound that is
unequal in its ability to dissolve or disperse cellular
components and to provide a suitable milieu for the various
metabolic reactions of a cell.
9. Autotrophic Bacteria
a) Autotrophic bacteria synthesize their own food from simple inorganic
compound
b) In this process, energy is obtained from either sunlight or chemically by
the oxidation of some inorganic substances like iron, sulphur, nitrogen
compounds, etc.
c) Food synthesized by autotrophic organisms is used for their growth and
metabolism.
d) Autotrophic bacteria are further divided into two types depending upon
the energy utilization.
10. A. Photosynthetic Bacteria
• a) These bacteria have a green sunlight trapping pigment
called bacteriochlorophyll, which captures sunlight.
b) These bacteria are found in the upper layer of ponds or
lakes.
c) Bacterial photosynthesis does not release oxygen; such
photosynthesis is known as anoxygenic photosynthesis.
d) Hydrogen is provided by the donor substance hydrogen
sulphide, and the by-product is sulphur, not oxygen.
e) These are again divided into two types:
11. A. Photosynthetic Bacteria
• i) Green Sulphur Bacteria
In this type of bacteria, photosynthetic pigment is chlorobium
chlorophyll, which uses hydrogen sulfide as a hydrogen donor and by-
product is sulphur. Example: Chlorobium.
• ii) Purple Sulphur Bacteria
The photosynthetic pigment in this process is bacteriochlorophyll
present in the chromatophores, and the by-product is sulphur.
Example: Chromatium.
12. B. Chemosynthetic Bacteria
• a) Chemosynthetic bacteria prepare their food by using
inorganic raw material in the absence of photosynthesis
pigment.
b) In this process, chemical energy is obtained from the
oxidation of certain inorganic substances such as ammonia,
nitrates, ferrous iron, hydrogen sulphides, and some
metallic and nonmetallic substances.
c) In this reaction, chemical bonds are broken, and
exothermic energy is released, which is used to drive the
synthetic processes of the cell.
d) These are again divided into the following types:
13. B. Chemosynthetic Bacteria
• i) Sulphur Bacteria (Sulphomonas)
These types of bacteria oxidise elemental sulphur or H2S and release
sulphuric acid or sulphur.
2S + 2H2O +3O2--------> 2H2O + 2S + Energy
Example: Thiobacillus denitrificans
Or, 2H2S + 4O2 ------> 2H2O + 2S + Energy
Example: Beggiatoa
• ii) Hydrogen Bacteria (Hydromonas)
In this process, molecular hydrogen is oxidized into water.
2H2 + O2 ------> 2H2O + Energy
4H2 + CO2 ------> 2H2O + CH4 + Energy
Example: Hydrogenomonas, Pseudomonas.
14. B. Chemosynthetic Bacteria
• iii) Iron Bacteria (Ferromonas)
They use chemical energy by oxidation of ferrous compounds into the
ferric compounds.
4FeCO3 + 6H2O + O2 ------> 4Fe (OH)3 + 4CO2 + Energy
Example: Thiobacillus, Ferrobacillus, etc.
• iv) Methane Bacteria (Methanomonas)
These types of bacteria get their energy from the oxidation of
methane; by-products are water and carbon dioxide.
15. B. Chemosynthetic Bacteria
• v) Nitrifying Bacteria (Nitrosomonas)
Bacteria get their energy by oxidation of nitrogen compounds into
nitrates.
2NO2 + O2 ------> 2NO3 + Energy
Example: Nitrobacter, Nitrosomonas.
• vi) Carbon Bacteria:
These types of bacteria oxidize CO into CO2.
2CO + O2 ------> 2CO2 + Energy
Example: Bacillus oligocarbophillous
16. 2. Heterotrophic Bacteria
• a) These types of bacteria are not capable of synthesizing their own
food. Thus, they live where organic food is readily available either
from living organisms or from organic substances.
b) Most of the pathogenic bacteria of humans, other plants, and
animals are heterotrophs.
c) Heterotrophic bacteria don’t have pigment, so they cannot
capture solar energy.
d) Some heterotrophic bacteria have simple nutritional
requirements, while few bacteria require a complex nutritional
requirement or specific nutrients like amino acids for their survival.
Such organisms are called fastidious heterotrophs.
e) Heterotrophic bacteria are of three types:
17. A. Saprophytic Bacteria
• a) These types of bacteria obtain food by decomposing dead bodies,
excreta of animals, dead plants, and their parts.
b) They secrete enzymes that break down complex organic
compounds into simpler products.
c) Breakdown of carbohydrates is called fermentation, and
breakdown of protein is called putrefaction.
d) Examples of these types of bacteria are Bacillus mycides,
Acetobacter, etc.
18. B. Parasitic Bacteria
• a) Parasitic bacteria live on and within other organisms, and they
obtain nutrition from their host.
b) Some parasitic bacteria cause diseases, and they are called
pathogenic bacteria, while others do not cause diseases but harm
the host.
c) Example: Vibrio cholerae, Diplococcus pneumoniae, etc.
19. C. Symbiotic Bacteria
• a) Symbiotic bacteria live in close association with other living
organisms so that they both benefit from each other. Neither of
them is harmed.
b) Symbiotic bacteria fix free atmospheric nitrogen into nitrogenous
compounds which are utilized by the plants, and in return, the plant
gives nutrients and protection to the bacteria.
c) Nitrogen-fixing bacteria like Rhizobium that live in the root
nodules of leguminous plants are examples of symbiotic bacteria.
