for B.PHARM 3rd sem

1. CULTURE MEDIA
USED
IN MICROBIOLOGY

2. Microbiological culture
Microbiological culture:
 Method of cultivating microbial organisms by letting them reproduce in
predetermined culture media under controlled laboratory conditions.
Culture media:
 The food material or substances required for growing microorganisms in vitro
(outside the body) is called culture medium.
Reasons for bacterial cultural:
 Bacteria have to be grown (cultured) for them to be subsequent clinical diagnosis.
 Culturing bacteria is also the initial step in studying its morphology and its
identification.
 By appropriate procedures they have to be grown separately (isolated) on culture
media and obtained as pure for study.
 Bacteria have to be cultured in order to obtain antigens from developing
serological assay for vaccines.
 Certain genetic studies and manipulations of the cells also need that bacteria be
cultured in vitro.
 Culturing on solid media is another convenient way of separating bacteria in mixture

3. Cultural media

4. History of culture medias
• Louis Pasteur used simple broths made up of urine or meat
extracts.
• Robert Koch realized the importance of solid media and
used potato pieces to grow bacteria.
• It was on the suggestion of Fannie Eilshemius, wife of
Walther Hesse (who was an assistant to Robert Koch) that
agar was used to solidify culture media.
• Before the use of agar, attempts were made to use gelatin
as solidifying agent. Gelatin had some inherent
problems….
 It existed as liquid at normal incubating temperatures (35-
37°C)
 Digested by certain bacteria

5. Properties of Agar
• Golden –yellow granular powder
• Used for preparing solid medium (solidifying
agent).
• Obtained from different seaweeds algae.
• No nutritive value.
• Not affected by the growth of the bacteria.
• Resistance to action of all microorganisms.
• Melts at 95°-98°C & remain liquid upto 40°-
42°C
• It gets solidified below 40°C
• 2% agar is employed in solid medium
• Easily available and economical

6. Composition of nutrient agar

7. Common ingredients of media
Water:
• Act as a vehicle, pure or distilled water, all enzymatic controlled chemical reactions
occur, copper distilled water can’t use.
Peptone:
• Act as buffer
• Hygroscopic in nature
• Partially digested proteins obtained from meat, heart muscle, casein, fibrin, soya meal,
etc.
• Nitrogen source
• Protease, amino acids, inorganic salts and growth factors-nicotinic acid and riboflavin.
Yeast:
• Prepared from cells of baker’s yeast or Saccharomyces
• Contains carbohydrates, amino acids, growth factor(vit. B group)
• Used as Vit. Source
Meat extract:
• Prepared from fresh lean meat
• Contains gelatin, proteoses, amino acids, creatin, creatinine, purine, minieral salts,
carbohydrates and Vit. B group

8. Types of Culture media
1. Classification based on physical
state(consistency)
2. Classification based on oxygen
requirement
3. Classification based on the chemical
composition
4. Classification based on functional
types

9. Types of culture media
I. Classification based on physical
state (consistency)
A) Solid medium- 2% agar. -
B) Semi solid medium – 0.2-0.5% agar
C) Liquid medium- – absence of agar

10. A) Solid medium:
• Agar is the most commonly used solidifying agent.
• 1.5-2.5% agar
• An agar plate is a Petri dish
• Ex: Nutrient agar
What is agar
• Golden –yellow granular powder
• Used for preparing solid medium(Solidfying agent).
• Obtained from different seaweeds algae.
• No nutritive value.
• Not affected by the growth of the bacteria.
• Resistance to action of all microorganisms.
• Melts at 95°-98°C & remain liquid upto 40°-42°C
• It gets solidified below 40°C
• 2% agar is employed in solid medium
• Easily available and economical

11. B) Semi-solid media
• Such media are soft and are
useful in demonstrating
bacterial motility and
separating motile from non-
motile strains.
• 0.2-0.5% agar
• Ex: Nutrient broth
containing 0.5% agar
C) Liquid media
• Absence of agar
• Referred as “ broth”.
• Bacteria grow uniformly
producing general turbidity
• Ex: fluid thioglycollate broth

12. Based on physical state

13. 2. Based on oxygen requirement
A) Aerobic media:
• Aerobic media are used to
grow aerobic microbes
• Ex: MacConkey’s broth,
Mannitol salt agar.
B) Anaerobic media:
• Anaerobic media are used to
grow anaerobic microbes.
• Ex: Robertson’s cooked meat
medium
• Link:http://www.scharlabmagyarorszag.
hu/katalogus/02-118_TDS_EN.pdf

14. 3. Based on the chemical composition
A) Simple media/Basal media
• Eg: Nutrient broth, Nutrient agar
• Nutrient Broth consists of peptone, meat
extract, NaCl,
• NB + 2% agar = Nutrient agar
• Used to isolate separate colonies for studying
1.Colony morphology.
2.Pigmentation.
3.Biochemical identification test

16. B) Synthetic or defined media:
• Chemically defined
• Media includes peptone water and nutrient broths
• 2% agar media
• Specially prepared media from pure chemical
substances for the research purpose
• Composition of every component is well known
• Ex: Peptone water(1% peptone+ 0.5% Nacl in
water
C) Non-synthetic, undefined and complex media:
• Chemically not defined
• Contains complex materials
• Exact chemical composition of this media is not
known
• Ex: Blood agar, TSA, Milk agar, yeast extract
broth.
• Contains at least one component that is neither
purified nor completely

17. D) Depending on functional type:
i) Enriched media
ii) Enrichment media
iii) Selective media
iv) Indicator media
v) Differential media
vi) Sugar media
vii) Transport media
viii)Assay media
ix) Storage media
 Write short note on the following media
highlighted by red colour above.