1. Prof. Dalia M. mohsen Prof. in Microbiology
Culture media(1)
Prof. Dalia M. mohsen
Prof. in Microbiology
Lecture (1)
Prof. Dalia M. Mohsen

2. Lecture (1)
Prof. Dalia M. Mohsen

3. Objectives Introduction to culture media
Common consistent of culture media
Different methods of Classification
Classification based on concentration of agar
Prof. Dalia M. Mohsen

4. Introduction
The study of microorganisms requires techniques for isolating from natural sources and growing them in the laboratory on synthetic media.
culture medium:-
Liquid or gel.
Support the growth of microorganisms .
Microbiologists use bacterial culture media for many purposes and applications
isolate and identify of bacteria.
long-term storage of pure cultures.
Antibiotic sensitivity test.
Prof. Dalia M. Mohsen

5. The important reasons for culturing bacteria in vitro
Diagnosing infectious diseases.
Studying its morphology and its identification
Obtain antigens from developing serological assays or vaccines
Genetic studies
Prof. Dalia M. Mohsen

6. Basic Composition of culture media
When culturing bacteria:- It is very important to provide similar environmental and nutritional conditions
bacteria need the basic nutritional conditions to grow
in-vitro, include:
Amino Acids
Carbohydrates
Vitamins
Fatty acids
inorganic salts
Water
Prof. Dalia M. Mohsen

7. Are the building blocks of proteins.
1.Amino acid:
Are the building blocks of proteins.
‘Essential’ amino acids must be added to culture media as cells are not able to synthesize these themselves.
Example: cystine, leucine, lysine, methionine, phenylalanine, tryptophan, and valine.
2. Carbohydrates
The main source of energy is derived from sugars.
The major sugars used are glucose and galactose, however, some media contain maltose or fructose.
Prof. Dalia M. Mohsen

8. Serum is an important source of vitamins in culture media.
Many vitamins needed by bacteria especially group B vitamins, are necessary for cell
4. Fatty Acids and Lipids
Are important in serum free media since they are normally present in serum e.g. cholesterol and steroids essential for specialized cells.
Prof. Dalia M. Mohsen

9. The inclusion of inorganic salts in media performs several functions.
Primarily they help to retain the osmotic balance of the cells and help regulate membrane potential by provision of sodium, potassium and calcium ions.
6. Water
All bacteria require some amount of water.
Buffering Systems
Most bacteria require pH conditions in the range and close control of pH is essential for optimum culture conditions.
Prof. Dalia M. Mohsen

10. Classification
Bacterial culture media can be classified in at least three ways;
Based on consistency
Based on nutritional component
Based on its functional use.
Classification based on consistency, Culture media are
liquid
semi-solid
solid
biphasic.
Prof. Dalia M. Mohsen

11. Liquid media:
These are available for use in test-tubes, bottles or flasks, sometimes referred as “broth” (e.g nutrient broth).
In liquid medium, bacteria grow producing turbidity.
Certain aerobic bacteria and those containing fimbriae (Vibrio & Bacillus) are known to grow as a thin film called ‘surface pellicle’ on the surface of broth.
Inoculating in the liquid medium also helps to dilute any inhibitors of bacterial growth (blood cultures).
The growth of the bacteria on the fluid media give either granular or uniform turbidity
Sometimes the initial turbidity may be followed by clearing due to autolysis, which is in penumococci.
Prof. Dalia M. Mohsen

12. Sterile Liquid media(right) turbid liquid media(left)
Prof. Dalia M. Mohsen

13. Liquid media show the surface pellicle
Prof. Dalia M. Mohsen

14. It melts at 90-95C and solidifies at 32–39 C.
Solid media:
Any liquid medium can be rendered by the addition of certain solidifying agents. Agar agar (simply called agar) is the most commonly used solidifying agent.
Agar is a polysaccharide obtained from the cell membranes of some species of red algae
It melts at 90-95C and solidifies at 32–39 C.
it is used at concentration of 1.5% w/v to make a solid agar medium.
Solid media are used mainly in Petri dishes as plate
Also in bottles or tubes as stab (deeps) or slope cultures.
Prof. Dalia M. Mohsen

15. Solid media in petri-dish
Prof. Dalia M. Mohsen

16. Semi-solid agar:
Reducing the amount of agar to % renders a medium semi-solid
useful in demonstrating bacterial motility
Common example include:- Transport media such as Stuart’s and Amies media.
Prof. Dalia M. Mohsen

17. Motility test in semi-solid media
Prof. Dalia M. Mohsen

18. Identify?
Prof. Dalia M. Mohsen

19. Biphasic media:
Sometimes, a culture system comprises of both liquid and solid medium in the same bottle. This is known as biphasic medium (e.g. Castaneda system for blood culture).
Prof. Dalia M. Mohsen

20. Biphasic Medium
Prof. Dalia M. Mohsen

21. Besides agar, egg yolk and serum can be used to solidify culture media
Besides agar, egg yolk and serum can be used to solidify culture media. While serum and egg yolk are normally liquid, they can be rendered solid by coagulation using heat.
Serum containing medium such as Loffler's serum slope and egg containing media such as Lowenstein Jensen medium and Dorset egg medium are solidified as well as disinfected by a process of inspissations
Define inspissations???
Prof. Dalia M. Mohsen

22. Loffler's serum & LJ
Prof. Dalia M. Mohsen

23. Prof. Dalia M. Mohsen