Lecture slides on Bacterial physiology by Dr. Shireen Rafiq (RMC)

1. Bacterial Physiology
Dr Shireen Rafiq
MBBS, M.Phil, Ph.D

2. Growth cycle
• Bacteria reproduce by BINARY FISSION
• Exponential growth---logarithmic growth

5. Definitions
• Aerobic bacteria
• Adequate amount of oxygen enhances
metabolism and growth
• Oxygen generates two toxic metabolites
hydrogen peroxide and superoxide ----bacteria
require enzyme superoxide dimutase and
catalase----catalyses the reaction

6. Obligate Aerobes
• Require oxygen to grow----as ATP generating
system is dependent on oxygen as the
hydrogen acceptor
• E.g. Mycobacterium tuberculosis

7. Facultative anaerobes
• Utilize oxygen if present to generate energy by
respiration
• Can use fermentation pathway to synthesize
ATP in the absence of sufficient oxygen

8. Obligate Anaerobes
• Can not grow in the presence of oxygen
• Lack superoxide dismutase or catalaze or both

10. Obligate Aerobes
• They require oxygen to grow----ATP generating
system is dependent on oxygen as hydrogen
acceptor
• E.g. Mycobacterium tuberculosis

15. Bacterial Culture Media

16. Microbiological Culture Media
• Culture media are mixtures of
nutrients for growth of micro
organism outside their natural
habitat.
• They supply the organism with
sources of energy and elements
allowing its optimum growth.

17. Culture and Medium
Culture is the term given to microorganisms that are
cultivated in the lab for the purpose of identifying
and studying them
Medium is combination of ingredients that will
support the growth and cultivation of
microorganisms by providing all the essential
nutrients required for the growth (that is,
multiplication) in order to cultivate these
microorganisms in large numbers to study them.

18. Microbiological Culture Media
• A- Water
• B- Nitrogen-containing compounds
• C- Energy sources
• D- Accessory growth factors
• E- Solidifying agents
• F- pH Indicators
• G- Reducing agents
• H- Selective agents

19. Classification of Culture media
• Based on the consistency:
Liquid -- Peptone water, Nutrient broth
Semisolid -- Nutrient agar stabs
Solid -- Blood agar, Serum agar
• Based on Oxygen requirement:
-- Aerobic medium
-- Anaerobic media

20. Aerobic media
Simple media- consists of only basic necessities
Liquid media
- Peptone water(1% peptone +0.5%Nacl + 100 ml water)
- Nutrient broth ( peptone water + 1% meat extract
Solid media
- Nutrient agar (nutrient broth + 2% Agar)
Use: To grow non-fastidious microorganisms

21. Aerobic Media
• Simple media
• Complex media
- Enriched media
- Differential media
- Enrichment media
- Selective media
- Sugar media
- Transport media

22. Basic Media
 Contain the essential requirements
for the growth of most micro
organisms
 Example:
1. Nutrient Broth / Agar
2. Nutrient Gelatin
3. Peptone Water
4. Sabouraud’s Dextrose Broth/ Agar

23. Enriched Media
• Contain nutrients (growth factors) required to support the
growth of a wide variety of organisms, including some of the
more fastidious ones.
• These factors are usually body fluids .
Example:
1. Blood Agar
2. Chocolate Agar (streptococcus pneumoniae)
3. Loeffler’s Serum (Corynebacteria , shows
proteolytic activity)
4. Dorset’s egg medium (Mycobacteria)

24. Selective Media
• These media contain a
substance that 1.
inhibits the growth of
some micro organism
2. while allowing the
growth of others
• i.e. they select for
certain microbes.
Example:
1. Lowenstein-Jensen
(Mycobacterium
tuberculosis)

25. Selective and Differential Media
• These are both selective & differential.
Example:
1. Mannitol Salt Agar (MSA)
2. Eosin Methylene Blue Agar (EMB)
3. Deoxycholate Citrate Agar (DCA)
4. Thiosulfate Citrate Bile Salts Medium
(TCBS)
5. Triple Sugar Iron Agar (TSI)
6. Bismuth Sulfite Agar (BS)

26. Transport media
• Stuart’s medium contain reducing agents to
prevent oxidation.
• Charcoal to neutralize certain bacterial
inhibitors to Gonococci,
• Amies transport media
• Cary blair media

27. Blood culture media
• - Brain-heart infusion medium
- In general
• - Mac Conkey’s Biphasic medium
- Glucose broth - Streptococci
- Bile broth - Salmonella
- Casteneda Biphasic M - Brucella