2. Introduction
• All living organisms require food and energy for proper
growth and development.
• Microorganisms (or microbes) vary significantly in terms of
the source, chemical form, and amount of essential elements
they need.
• Some examples of these essential nutrients are carbon, oxygen,
hydrogen, phosphorus, and sulfur.
3. Mineral Nutrients
• The microbial nutrients can be classified into two types:
Macro (major) nutrients,
Micro (minor) nutrients.
• It is also known as trace elements on the basis of their amount
required.
4. Macro Nutrients
• The microbial cells contain water accounting for some 80-90%
of their total weight.
• The water is always the major essential nutrient in
quantitative terms.
• The solid matter of cells contain other macro elements such as
carbon, nitrogen, phosphorus, sulphur, potassium,
magnesium, sodium, calcium and iron in addition to oxygen
and hydrogen (derivable metabolically from water).
• About 95% of cellular dry weight of microbial cells is
accounted for only six macro elements (O, H, C, N, P and S).
• Carbon assumes great importance as the main constituent of
all organic cell materials.
5. • CO2 is the most oxidized form of carbon.
• The photo-synthetic microorganisms reduce CO2 to organic cell
constituents.
• On the other hand, all the non-photosynthetic microorganisms
obtain their carbon requirement mainly from organic nutrients
which contain reduced carbon compounds.
• These organic compounds not only provide the carbon for
synthesis but also meet the energy requirement by entering into
energy yielding metabolic pathways and are eventually oxidised
to CO2.
• Some microbes have the ability to synthesize all their cellular
components using a single organic carbon source.
• They also need other complex carbon containing components
which they cannot synthesize.
• These components are called growth factors and vitamins.
6. • Sulphur and nitrogen are taken up by most organisms.
• It reduced within the cell and utilized in other biosynthetic
processes.
• The sulphur and nitrogen requirements of most organisms
can also be met with organic nutrients such as amino acids.
• A few microorganisms are capable of reducing elemental
nitrogen to ammonia and this process of nitrogen assimilation
is known as biological nitrogen fixation.
7. • Most of the microorganisms need molecular oxygen for
respiration.
• The oxygen serves as terminal electron acceptor, and such
organisms are referred to as ‘obligate aerobes’.
• There are a few organisms which do not use molecular
oxygen as terminal electron acceptor.
• These microbes are called ‘obligate anaerobes’.
• Aerobes which can grow in the absence of oxygen are called
‘facultative anaerobes’ and the anaerobes which can grow in
the presence of oxygen are referred to as ‘facultative aerobes’.
8. • The microorganisms do not use only macro elements but also
others like cobalt, copper, manganese, molybdenum, nickel,
selenium, tungsten, vanadium and zinc which are required by
all microorganisms.
• These elements are often referred to as minor nutrients or trace
elements.
• They are metals playing the role of cell’s catalysts and many of
them are play a structural role in various enzymes.
• Some microorganisms need additional specific mineral
nutrients, for example, diatoms and some microalgae require
silica, supplied as silicate, to impregnate their cell walls.
Micro Nutrients
9. Growth Factors:
• Besides the mineral nutrients, the microorganisms need some
organic compounds.
• Most of the microorganisms are capable of synthesizing these
organic compounds from simpler carbon resources.
• Others m.or. cannot and need their supply from outside for their
proper growth and development.
• Organic nutrients of this type are known collectively as growth
factors (essential metabolites).
• It can be categorized into three groups (amino acids, purines
and pyrimidines and vitamins) on the basis of their chemical
structure and metabolic function.
• Growth factors fulfill specific needs in biosynthesis of certain
molecules, they are needed in very small amounts.
10. Nutritional types of M.or.
All organism require energy source and electrons for growth apart
from C, H, O.
1) Carbon source:
Autotrophs- use CO2 or biosynthetic carbon sources.
Heterotrophs- use reduced organic molecule from other
organism.
2) Energy source:
Phototrophs- use light as their energy source.
Chemotrophs- obtain energy from oxidation of chemical
compound.
3) Electron source:
Lithotrophs- use reduced inorganic substances as electron
source.
Organotrophs- use electron from organic compound.
11. Microbes can be classify based on carbon, energy and electrons.
Photo-lithotrophic autotrophs or photo-lithoautotrophs:
Eg.- algae, cyanobacteria, purple and green sulphur bacteria
Photo-organoheterotrophs:
Eg.- purple and green non sulphur bacteria
Chemo-lithoautotrophs:
Eg.- sulphur oxidizing bacteria, hydrogen bacteria, nitrifying
bacteria, iron oxidizing bacteria
Chemo-organoheterotrophs:
Eg.- protozoa, fungi, non photosynthetic bacteria, pathogen
12. Types of microbes based on nutrition
1) Autotrophs:
It use CO2 as main component.
Many microbes are photosynthetic and autotrophs.
It use light as energy sources.
Some autotrophs oxidize inorganic molecule and drives
energy from electron transfer.
Eg. Phptoautotrophs, Chemoautotrophs
2) Heterotrophs:
It use reduced organic molecule as carbon source.
Glycolytic pathway produce C for in biosynthesis and
release energy as ATP and NADH.
Eg. Saprophytic, Symbiotic, Parasitic bacteria
13. Autotrophic nutrition: It consist of organic material
formation from inorganic raw material with the help of
energy.
Example: Chemoautotrophs
Photoautotrophs
Heterotrophic nutrition: It use readymade organic
nutrients and does not require energy.
Example: Saprophytic
Symbiotic
Parasitic
14. Photoautotrophs
They are versatile in nature.
They are photosynthetically.
It can be cocci, bacillus and spirilla shaped.
They have two types of pigment.
• Bacteriochlorophyll: it include purple sulphur bacteria.
Eg. Thiopedia Rosea
Rhodopseudomonas
• Chlorobium chlorophyll: it also known as
bacteriopheophytin. It include green slphur bacteria.
Eg. Chlorobium limicula
15. • It use inorganic raw material for synthesis of organic food.
• It require energy for the oxidation of inorganic substances.
Nitrifying bacteria:
Nitrosomonas, Nitrococcus, Nitrobacter, Nitrocystis
Sulphur oxidizing bacteria:
Baggiota- colourless sulphur bacteria
Thiobacilus thiooxidanse
Iron bacteria: It convert ferrous compouund to ferric
compound.
Ferrobacilus ferrooxidance
Chemoautotrophs
16. • It is free living anaerobic m.or.
• It obtain food from remaining organic substances.
• It secrete digestive enzyme which breakdown of complex
insoluble substances in to simple soluble component.
• They are useful or harmful. They can spoil of food items and
denitrification of soil.
• It may be present in animal excreta, fallen leaves, vegetables,
jam, jelly, plant and animal product.
• Anaerobic oxidation of carbohydrate: fermentation
• Anaerobic oxidation of protein: putrefaction
• Anaerobic oxidation of organic compound: decay
Saprophytic bacteria
17. • They lives in association with other organisms.
• Enteric bacteria: E.coli present in human intestine, it is
symbiont and use our food stuff and generate vitamin B & k.
• Rhizobium: it is associated with legumes, also freely present.
It can enter in to root of legume, multiply there and form
nodules. These bacteria obtain food from legumes. it perform
nitrogen fixation in root nodules.
• Nitrogen fixing symbiont bacteria: these bacteria can fix
atmospheric nitrogen and lives symbiotic relation with plants.
• Example: Frankia, Xanthomonas
Symbiotic bacteria
18. • These bacteria lives in contact with other bacteria or host.
• It require organic matter to grow and maintenance.
• It has several modification to overcome barrier of defense
system of host.
• It can release various component that affect the host system.
• Connective tissue break- by Algressin
• Cell wall break down- by cellulose
• Killing host phagocytes- leucocidins
• Prevent blood clotting- streptokinase
• These compound may be useful or harmful for host.
• Parasitic bacteria may or may not cause disease.
• It release two type of toxins: endotoxin and exotoxin, that
breakdown host cell.
Parasitic bacteria
