Media for bacterial growth.pptx

1. Media for bacterial Growth

2. Culture Media
◌Culture media, also known as growth media, are specific mixtures of
nutrients and other substances that support the growth of
microorganisms such as bacteria and fungi (yeasts and molds).

3. Culture media
◌Gives artificial environment stimulating natural conditions
necessary for growth of bacteria

4. Culture media
The basic requirement of culture media:
◌Energy source
◌Carbon source nitrogen source salts like sulfate, phosphate,
chlorides and carbonates of sodium, potassium, magnesium,
ferric, calcium, trace elements like copper, etc,.
◌Satisfactory pH 7.2 -7.6
◌Adequate oxidation reduction potential
◌Growth factor like tryptophanfor salmonella typhi, glutathione
for gonococci, X and V factors for hemophilus

5. Characteristice of ideal Culture media
◌Must give satisfactory growth from single inoculum
◌Should give rapid growth
◌Should be easy to grow
◌Should be reasonably cheap
◌Should be easily reproducible
◌Should enable to demonstrate all characteristics in which we are
interested

6. Classification Culture media
I. Based on consistency
1. Solid media
2. Liquid media
3. Semisolid media

7. Classification Culture media
II. Based on constituent
1. Simple media
2. Synthetic media or defined media
3. Complex media
4. Special media

8. Classification Culture media
Special media further divided into
1. Enriched media
2. Enrichment media
3. Selective media
4. Indicator or differential media
5. Sugar media
6. Transport media

9. Classification Culture media
III. Aerobic media and anaerobic media

10. Solid media
• Used to study colonies of individual bacteria
• Essential for isolation of organism in pure form

11. Solid media –Agar
• Important constituent of solid media
• Complex polysaccharides obtained from seaweeds
• Melts at 80* to 100* C
• Solidifies at 35-42* C
• Does not provide any nutrition to the bacteria
• Acts only as solidifying agent
• Not metabolized by any pathogenic bacteria

12. Solid media –gelatin
• Prepared by hydrolysis of collagen with boiling water
• Liquid form at 37*C
• Transparent gel form at 25*C
• The main use of gelatin is to test the ability of bacteria to liquefy it.
• Blackening of media indicates hydrogen sulfide production

13. Liquid or fluid media
◌Bacteria grow very well in fluid media in 3 to 4 hours
◌Used as enriched media before plating on solid media
◌They are not suitable for the isolation of organism
◌Cannot study colony characteristics
◌Nutrient broth, peptone water etc.

14. Liquid or fluid media -broth
1. Infusion broth :
◌Fat free minced beef meat is added to water and kept in
refrigerator overnight
◌Fluid obtained after removal of meat is boiled for 18minutes
◌Peptone and 0.5% sodium chloride is added

15. Liquid or fluid media -broth
2. Meat extract broth :
◌Commercially available as lab Lemco
3. Digest broth
◌Prepared from meat by enzymatic (trypsin, pepsin) action
◌It is more rich than infusion and extract broth
◌Addition of peptone is not required in digest broth
◌More economical

16. Liquid or fluid media -broth
4. Yeast extract:
◌Prepared by extracting autolyzed yeast with water
◌High content of vitamin B

17. Liquid or fluid media
Peptone
◌It is protein partially digested with hydrolytic enzymes like
pepsin, trypsin, papain etc,.
◌It supplies nitrogenous material and also act as a buffer
◌Several bacteria can grow in 1% peptone water
◌Constituents of peptone: proteoses, polypeptides and amino acids

18. Liquid or fluid media
Other examples
◌Sugar media (1% sugar in peptone water)
◌Glucose broth (1% glucose in nutrient broth)
◌Bile broth (0.5% bile salts in nutrient broth)
◌Hiss serum (1 part serum & 3 part glucose broth)
◌Liquid Mac Conkey
◌Gylcerol saline
◌Enrichment (tetrathionate and selenite)

19. Simple media / basal media
◌Consist meat extract , peptone, sodium chloride and water
◌Peptone water: it is prepared by adding 1g peptone, 0.5g sodium
chloride to 100ml of distilled water
◌Nutrient agar : addition of 2% agar in nutrient broth constitute
nutrient agar

20. Complex media
◌Consist ingredient of special purpose
◌For binging out certain characteristics
◌Providing special nutrient required for the growth of certain
organism

21. Synthetic media
◌Prepared solely from pure chemical substances and exact
composition of medium is known
◌Used for research purpose

22. 1. Enriched Media Special media
◌Substance like blood, serum or egg is added to basal medium,
◌e.g.,: blood Agar, chocolate Agar, egg media, Loeffler serum slope

23. 2. Enrichment Media Special media
◌Some inhibiting substances are added in liquid media with the
result that wanted organism grow more in number than
unwanted organism
◌E.g., : selenite F broth, tetrathionate broth

24. 3. Selective Media Special media
◌Same as enrichment media
◌Inhibiting substance is added to solid media
◌E.g., : deoxycholate citrate medium which contains nutrient Agar,
sodium deoxycholate, sodium citrates lactose and neutral red

25. 4. Indicator Media Special media
◌Contains one indicator which changes color when bacterium
grow in them
◌E.g., : salmonella typhi reduces sulphite to sulphide in Wilson
and blair medium
◌(colonies of salmonella typhi have black and metallic sheen)

26. 5. Differential Media Special media
◌A medium which has substance enabling it to bring out differing
characteristics of bacteria thus helping to distinguish between
them
◌E.g.: MacConkey’s medium (peptone, lactose, agar, neutral red
and taurochocolate)
◌It shows lactose fermenter as red colonies while nonlactose
fermenter as pale colonies.

27. 6. Sugar Media Special media
• Usual sugar media consist of 1% sugar concerned, in peptone
water along with appropriate indicator
• A small tube is kept inverted in sugar tube to detect gas
production.

28. 7. Transport Media Special media
◌Delicate organism like gonococci which may not survive the time
taken for transporting the specimen to the laboratory or may be
overgrown by non pathogen (dysentery or cholera
organism)special medium is required called transport media
◌E.g.: Stuart medium for gonococci and glycerol saline for stool

29. 8. hiss’s Serum Special media
◌25% serum is used for organism which are exacting in their
growth requirement
◌e.g.: pneumococci

30. Anaerobic media
◌Media used to grow Anaerobic organisms
◌E.g., Robertson’s cooked meat media
◌Indicator used is reduced methylene blue (NaOH (sodium
Hydroxide, methylene blue, glucose)

31. Aerobic cultures
◌Aerobic cultures are continuously sparged with air.
◌Most components of air are inert and leave directly through the
exhaust gas line.
◌If air entering the fermenter is dry, water is continually stripped
from the medium and leaves the reactor as vapor.
◌Over time, evaporative water loss can be significant.