Microbial Culture Media Composition Part-1

Microbial Culture Media Composition Part-1

In nature, their are a variety of micro-organisms present and every single organism has some specific growth requirements like suitable temperature, pH, salt concentration nutrient requirements etc.

If we want a desired culture of micro-organism we should provide them with the optimum and required growth conditions. On the basis of requirement of different micro-organism, numerous media composition are designed.

Some media compositions listed below.

( Here gm indicates gram and ml indicates millilitre)

1. Peptone broth
Peptone -1 gm
Distil water - 100 ml
NaCl -0.5 gm
pH -  7

Role

a)   Peptone- Peptone is a source of carbon, Nitrogen and sole source of energy.
b)   NaCl- It maintains osmotic balance between cell and media.
c)    pH – It is the hydrogen ion concentration of media.

2. Nutrient agar
Peptone -1 gm
Meat extract -0.3 gm
NaCl -0.5 gm
Distil water -100 ml
pH -7
Agar-agar -2.5 to  3 gm

Role

a)  Meat extract- It supplies amino-acid, growth factors to the cell.
b)  Agar-agar – It is a solidifying agent used to solidify media.

3. Milk agar
Peptone -1 gm
Meat extract -0.3 gm
NaCl -0.5 gm
Distill water -90 ml
pH -7
Agar-agar -2.5 to  3 gm
Skimmed milk -10 ml

Note – The media components and skimmed milk should be sterilized separately and after sterilization, the skimmed milk is added in nutrient media components in aseptic condition.

4. Starch agar
Soluble starch -0.5 gm
Peptone -0.5 gm
Meat extract -0.5 gm
Distil water -100 ml
pH -7
Agar-agar -3 gm

Role

a) Starch is a polysaccharide and this media is used for the detection of enzyme amylase by using starch hydrolysis test.

5. MacConkey's agar
Petone -2 gm
Sodium taurocholate -0.5 gm
10 % Lactose sugar -1 gm
Distil water -100 ml
Agar-agar -3 gm
pH -7.2
Indicator -Neutral red 0.3 ml

Role

a) MacConkey’s agar is used for isolation Gram-negative enteric bacteria.
b) Peptone is a  source carbon, nitrogen and energy.
c) Sodium taurocholate is a bile salt it inhibits the growth of gram-positive and some fastidious gram-negative bacteria.
d) Lactose is a source of carbohydrate.

6. Tryptone broth
Tryptone -1 gm
NaCl -0.5 gm
Distil water -100 ml
pH -7.5

Role

a) Tryptone broth is used in a biochemical test called as indole production test.

7. Sabourauds agar
Glucose -4 gm
Peptone -1 gm
Distil water -100 ml
Agar-agar -3 gm
pH -5.4

Role

a) Sabourauds agar is used for isolation and cultivation of fungal species.

8. Gelatin agar
Peptone -1 gm
NaCl -0.5 gm
Meat extract -0.3 gm
Gelatin -1 gm
Distil water -100 ml
Agar-agar -3 gm
pH -7.2
Role
a)  Gelatine agar is used in gelatin hydrolysis test for production of gelatinase enzyme.
A) Solution A ( 20 ml )
Bismuth ammonium citrate -30 gm
Sodium sulphate -100 gm
Di-hydrogen phosphate -100 gm
Glucose -50 gm
Distil water -1000 ml
B)  Solution B ( 45 ml )
Ferric citrate -2 gm
Brillant green -0.25 gm
Distil water -225 ml
C)  Solution C =  Complete media
Nutrient agar -100 ml
Solution A -20 ml
Solution B -4.5 ml

Role

a)  Wilson and Blair media is highly selective media for isolation of Salmonella species.
b)  In Wilson and Blair media, brilliant green and bismuth ammonium citrate do not allow growth of coliforms, Gram-positive bacteria and other lactose fermenting bacteria.
c)  Here glucose is a sole source of carbon.
d) Whereas ferric citrate neutralizes the toxicity of bismuth ammonium citrate.

10. Urea agar
Peptone -0.1  gm
NaCl -0.5  gm
K2HPO4 –0.2   gm
pH  -6.8
Phenol red -0.6   ml
Distill water -90    ml
10 % Glucose  -1     ml
20 %  Urea solution -10   ml
Agar-agar -3     gm

Note-Urea and glucose solution should be sterilized separately

Role

a)  Urea agar is used in a biochemical test call as urea hydrolysis test for detection of urease enzyme production.
b)   Peptone is a source of carbon, nitrogen and energy
c)    NaCl maintain osmotic balance.
d)    K2HPOacts as a buffer.
e)    10 % Glucose solution is a additional source of carbon.
f)      20 %  Urea solution is a additional source of nitrogen.

This was Microbial Culture Media Composition Part-1 you can get some more media composition in my post  Microbial Culture Media Composition Part-2.

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