TYPES OF CULTURE MEDIA USED IN MICROBIOLOGY

TYPES OF CULTURE MEDIA:

CULTURE MEDIA: - Culture media are an artificially prepared mixture of various nutrients for the growth and multiplication of micro-organism.

TYPES OF CULTURE MEDIA: - Culture media may be divided in different ways:-

A] Depending on physical state (According to media consistency):

1. Solid media

2. Semisolid media

3. Liquid media

B] Depending on oxygen requirement:

1. Aerobic media

2. Anaerobic media

C] Depending on chemical composition:

Simple or basal media.

Synthetic or defined media.

Non-synthetic or undefined or complex media.

D] Depending on functional type:

1. Enriched media

2. Enrichment media

3. Selective media

4. Indicator media

5. Differential media

6. Sugar media

7. Transport media

8. Assay media

9. Storage media

SOLID MEDIA: - Solid media is used for the isolation of bacteria as pure culture. Agar is most commonly used solidifying agent. Agar is a long chain polysaccharide obtained from seaweeds algae. It is golden yellow granular powder and not affected by the growth of the bacteria. It acts as good solidifying agent (1.5 to 2%). It melts at 95 to 98°C and remains liquid upto 40 to 42°C. bacteria grow to produce and form colonies. E.g. Nutrient agar.

SEMISOLID MEDIA:-Semisolid media are soft and are useful for demonstration of motility of bacteria and also for separation of motile from non motile strains. The concentrations of agar used in semisolid media are 0.2% to 0.5%. E.g. Nutrient broth containing 0.5% agar.

LIQUID MEDIA: - (Absence of agar) it is also called as “broth” bacteria grow uniformly producing general turbidity. E.g. Fluid thioglycollate broth.

AEROBIC MEDIA: - Aerobic media are used to grow aerobic micro-organism (Aerobic micro-organism requires oxygen for growth) E.g. MacConkey's broth.

ANAEROBIC MEDIA: - Anaerobic media are used to grow anaerobic micro-organism (Anaerobic micro-organism does not require oxygen or any other gases for growth).

E.g. Robertson's cooked meat medium.

SIMPLE MEDIA: - It may be used for growth (culture) of common bacteria that do not need enrichment of the media. These media includes peptone water, nutrient broths & nutrient agar.

Peptone water consist of peptone 1%, NaCL, and water.

Nutrient broth consists of peptone, meat extract, NaCl and water.

Nutrient agar consist of nutrient broth + 2% agar.

SYNTHETICOR DEFINED MEDIA: - These media is prepared from pure substances and the exact composition of the medium is known. These media is used for research purposes as well as metabolic studies of different micro-organisms. E.g. peptone water – 1% peptone + 0.5% NaCl in water.

NON SYNTHETIC OR COMPLEX MEDIA: -This media usually contains complex materials of biological origin such as blood or milk or yeast extract or beef extract. The exact chemical composition of this media is not known but it provides all the growth factors for the cultivation of unknown bacteria. These media may be added ingredients for special purposes for growth of specific microorganisms. It contains at least one component that is neither purified nor completely. E.g. Blood agar, Milk agar, Yeast extracts broth.

ENRICHED MEDIA: - These media are prepared for fastidious micro organisms & bacteria that are exacting in their nutritional needs.The media are enriched by addition of substances such as blood, serum & egg to simple medium. E.g. blood agar (Streptococcus), chocolate agar (Neisseria, Haemophilus).

Blood Agar: - It is prepared by adding 5-10% 0f sheep blood to the molten nutrient agar at 45⁰C. It is used to isolate fastidious organisms and detect hemolysis.

Chocolate agar: - It is prepared by adding 5-10% 0f sheep blood to the molten nutrient agar at 70⁰C. so that the RBC’^swill be lysed and the content of RBC’^swill be released. It is more nutrious than blood agar. It is used for growing fastidious bacteria such as Haemophilus influenza.

ENRICHMENT MEDIA: - In this liquid medium specific substance is added which inhibits the growth of unwanted bacteria and favors the growth of wanted bacteria.

E.g. Tetrathionate broth, selenite F broth. These media inhibits coliforms (e.g. Escherichia coli) by allowing growth of pathogenic cultures.

SELECTIVE MEDIA: - This is like enrichment media but is in a solid form. These media favour the growth of a particular bacterium by inhibiting the growth of undesired bacteria and allowing growth of desirable bacteria in the form of colonies. It requires maintaining physical conditions (temperature, pH, gaseous) of a culture media for growth of specific microorganisms.

E.g. MacConkey's agar media (Escherichia coli). It contains sodium taurocholate (bile salt) which selectively allows growth of Gram-negative bacteria by inhibiting Gram-positive bacteria.

Tellurite media (Tellurite inhibits the growth of most of the throat organisms except diphtheria bacilli). Lowenstein and Jensen medium (Mycobacterium tuberculosis).

INDICATOR MEDIA: - These media contain an indicator which changes colour when a particular bacterial species grows in them.

E.g. Blood agar and MacConkey agar Wilson and Blair medium, Salmonella typhi reduces sulphite to sulphide in the presence of glucose and the colonies have a black metallic shine.

DIFFERENTIAL MEDIA: - : A media which has substances incorporated in it to enabling it distinguish between different types of bacteria based on some observable characteristics.

E.g. MacConkey's medium (contains peptone, lactose, neutral red and taurocholate). It shows lactose fermenter as red colonies while non-lactose fermenter as white or pale colonies. MacConkey's medium is also called as indicator medium or selective media.

SUGAR MEDIA: - In this media 1% sugar & suitable indicator is added to peptone water. Durham’s tube is kept inverted in the tube containing media to detect gas production.

TRANSPORT MEDIA: - These media is used for transporting the media. There are some delicate microorganism which may not survive the time taken for transporting to the lab or may be overgrown by non pathogens (Escherichiea coli) and Pathogens (Shigella and salmonella species) for such types of delicate microorganism special media are devised. E.g. Amies transport media, Stuart’s transport media.

ASSAY MEDIA: - These media have specific composition and are used for the assay of vitamins, amino acids, and antibiotics.

E.g. antibiotic assay media are used for determining antibiotic potency by the microbiological assay technique.

STORAGE MEDIA: - These media used for storing the bacteria for a long period of time. Examples: Egg saline medium, Dorset’s egg medium, Blood agar slants, Blood agar stabs.

CLICK BELOW TOPIC TO READ

1. INTRODUCTION OF MICROBIOLOGY

2. BRANCHES OF MICROBIOLOGY

3. SCOPE OF MICROBIOLOGY

4. HISTORY OF MICROBIOLOGY {PART 1}

5. HISTORY OF MICROBIOLOGY {PART 2}

6. HISTORY OF MICROBIOLOGY {PART 3}

7. PROKARYOTES VS EUKARYOTES DIFFERENCES

8. MORPHOLOGY OF BACTERIA

9. ULTRASTRUCTURE OF BACTERIA

1. NUTRITIONAL REQUIREMENTS OF BACTERIA

1. RAW MATERIAL USED FOR CULTURE MEDIA