 Microbial cells are structurally complex.
 Organisms need nutrients & a source of energy,
also known as ‘MICROBIAL NUTRITION’ to carry
out numerous functions.
 NUTRIENTS are substances used in biosynthesis of
bacteria .
 So that microbial nutrition is directly proportional to
the microbial growth.
 Therefore Growth is impossible without nutrition.
THESE NUTRIENTS ARE CATEGORISED AS:1. MACRO-NUTRIENTS OR MACRO-ELEMENTS
2. OTHER MACRO-NUTRIENTS
3. MICRO-NUTIENTS OR TRACE EEMENTS
4. ORGANIC GROWTH FACTORS
5. LIGHT
6. WATER
1. THE MACRO-NUTRIENTS OR MACRO-ELEMENTS:o
o
o
carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur.
They are essential elements because they required in large amounts.
They contain 95% of dry weight of the microbial cells.
MACRONUTRIENTS
FUNCTIONS
CARBON
Needed for the skeletons & backbones of all the organisms,
molecules from which organisms are built.
OXYGEN &
HYDROGEN
Available from water added to culture media for growth and
found in organic molecules
NITROGEN
Nature component of protein & nucleic acid . Sources are
organic & inorganic nitrgeneous compound.
PHOSPHORU
S
needed as a part of nucleic acid, co-enzyme NAD & FLAVIN
& ATP.
SULPHUR
It forms apart from the structure of several co-enzyme.
They all are components of carbohydrates, lipids, proteins, nucleic acids.
NUTRIENTS
FUNCTIONS
POTASSIUM
Helps in activity by a no. of enzymes that is including some
involved in protein synthesis.
CALCIUM
Contributes to the heat resistance of bacterial endo-spores.
MAGNESIUM
Serves as a co-factor for many enzymes, complexes with ATP,
& stablize ribo-somes & cell membrane.
IRON
It is part of cyto-chromes & a co-factor for enzymes & electron
carrying protein.
 Micro-nutrients are needed in small amounts.
 These nutrients are:- Magnese, zinc, cobalt, nickel &
copper.
 Cells require such small amounts that contaminates
from water, regular media components often are
adequate for the growth.
 They are normally a part of enzymes & co-factors.
 They aid in the catalysis of reactions &
maintainence of protein structure.
Organic compounds that are essential cell
compounds or precursors of such components are
called ‘Growth factors’.
The major classes of growth factors are:1. AMINO ACIDS:- Needed for protein synthesis.
2. PURINE & PYRIMIDINE:- Helps in nucleic acid
synthesis.
 VITAMINS:- They are small organic molecules that
usually make up all or part of enzyme, co-factor &
are needed in only very small amounts to sustain
growth, also known as ‘bacterial vitamins’.
 Some bacteria’s synthesis their own vitamins & while
other need to take them from outside.
 This varies from bacteria to bacteria.

Micro-organisms need light ( 250- 250 nm) for the
photosynthesis of vitamins & minerals & for pigments.
6. WATER
 Water is important, because all nutrients should be in
solution form before they can enter in organisms.
ENVIRONMENT FACTORS: There are some environment factors which also
influenced to microbial growth. These factors are like: Air , Temperature, pH, Radiations, Osmotic pressure etc.
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INTRODUCTION:A Nutrient material prepared for the growth of microorganisms in a lab. Is called a ‘culture medium’.
Some bacteria can grow well on just about any
culture medium.
Others require special media & still others cannot
grow on any non-living medium yet developed.
When microbes are introduces into a culture medium
to initiate growth, they are called an ‘inoculum’.
The microbes that grow & multiply in or on a culture
medium , are referred to as ‘culture’.
 CULTURE MEDIA can be constructed completely
from chemically defined components (defined media
or synthetic media) or constituents like peptones &
yeast extract(complex media).
 Culture media can be solidifying by the addition of
agar, a complex polysaccharide from red algae.
 Culture media is needed to grow the organisms & the
constituents are:1. Water:- i.e. source of hydrogen & oxygen.
2. Electrolytes:- i.e. sodium chloride.
3. Peptone:- it is a complex mixture of partially digest
protein.
4. Meat extract
5. Blood or serum
6. Agar:- which is used in 2-3% constituent.
A small amount of protein & many
inorganic compounds.
TYPES OF MEDIA
S.
NO
BASED ON
PHYSICAL
NATURE
BASED ON
BASED ON
PRESENCE CHEMICAL
ON OXYGEN COMPOSITION
&
NITROGEN
BASED ON
FUNCTIONAL
TYPE &
SPECIAL
MEDIA
1
LIQUID MEDIA
e.g. nutrient broth
AEROBIC
ENRICHED:when basal
medium add
with other
medium, like
blood serum,
agar. E.g. for
growing
streptococus
2
SEMI-SOLID
MEDIA
e.g. soft agar
ANAEROBIC COMPLEX MEDIA :contain some
ingredients of
unknown
composition. Needed
for growth of bacteria.
E.g. nutrient broth
SIMPLE MEDIA:- W/c
is routinely applied on
the lab., To see motile
bac. , E.g. soft agar
ENRICHMENT:
- it has
stimulating
effect of a bac.
To grow or
inhibit its
compe-tatives.
3)
SOLID
MEDIA
e.g.
nutrient
agar
SYNTHETIC MEDIA:Prepared from pure
chemicals, & used
to study metabolic
requirement.
SELECTIVE:- help in the
isolation of a particular
species e.g. DCA agar
colony gives
deoxycholate
4)
DIFFRENTIAL:-it
diffrentiate b/w 2 bac’s. e.g.
Mackonkey’s agar
diffrentiate b/w lactose &
non-lactose fermenting.
5)
INDICATORS:- It s colour
change when a specific
bac. Grows on it. E.g
salmoneela .
6)
TRANSPORT:- For delicate
org. for transferring them.
7)
SUGAR:- Helps in
identification of bac..e.g.
glucose et. Are needed in
fermentation testhelps in
identifying.