This document provides an overview of microbiology practical concepts for a second year Lab Medicine course. It discusses bacterial nutritional requirements, types of culture media including their components and uses, culturing techniques, and optimal incubation conditions. Specifically, it covers the carbon, energy, nitrogen, mineral, and growth factor needs of bacteria, and describes basal, enriched, selective, enrichment, differential and transport culture media.

1. Second year Lab Medicine (Females)
1433- 1434 A.H. / 2012- 2013
Microbiology Practical (Course I)
.Mrs. Hibah Abdul-Wahab I
Abu-Sulaiman

2. Who will be her groom??!

3. Royal Dining Royal Atmosphere

6.  Bacterial nutritional requirements.
 Composition of culture media.
 Categories of culture media.
 Solidifying agents.
 Types of media.
 Media Quality control.
 Culturing techniques.
 Condition of incubation.

7. 1. Carbon Source:
◦ Heterotrphs: from organic compounds such as: a.a.,
polysaccharides, CHO, proteins and peptides.
◦ Autotrophs: from fixing inorganic carbon dioxide.
1. Energy Source:
◦ Phototrophs: from sunlight.
◦ Chemotrophs: from oxidation of chemicals.
1. Nitrogen: essential for a.a., nucleotide and
vitamins synthesis.

8. 4. Minerals: as cofactors in enzymatic reactions.
◦ E.g., sodium, potassium, calcium, magnesium, iron… etc.
4. Growth factors:
◦ Amino acids, a.a.: bacteria possess proteinases.
◦ Purines and pyrimidines: to be converted to nucleotides.
◦ Bacterial vitamins: for co-enzyme production.
4. Water:
◦ All metabolic functions of a bacterial cell are performed in
aqueous environment.
◦ Distilled water
 Tap water minerals and their reaction with peptones and meat
extracts.

9. 1. Water.
2. Peptone: product of protein hydrolysis.
◦ From animal proteins: source of nitrogen.
◦ From soya bean (plant) protein: source of carbohydrates,
CHO.
1. Meat extracts: as source of a.a. and other essential
vitamins and elements.
2. Yeast extract: as a stimulant for bacterial growth in
the media.
3. Mineral salts: for bacterial enzymes activity.
4. Carbohydrates: as source of carbon and energy.

10.  Agar:
◦ Is a complex polysaccharide (polymer of galactose) that
is extracted from the cell wall of seaweed (red algae).
◦ It has no nutritional value in agar cultures.
 Gelatin:
◦ A protein which is derived from collagen of skin and
bone.
◦ It has no nutritional value in agar cultures.

11. Consist of
Without agar With agar

12. Agar Slant Agar Deep
 Agar Plates

13.  In broths, bacterial growth is indicated by a
change in the appearance from clear to turbid
(cloudy).
 The more turbid, the….

14.  Basal Media:
◦ Simple media that will support the growth of most bacteria that
do not require special nutrient. E.g., Nutrient broth.
◦ Nutrient broth+ agar= Nutrient agar
 Enriched media:
◦ Culture media that are enriched with whole or lysed blood,
serum, special extracts or nutrient to support the growth of
those bacteria that cannot grow on the basal media.
◦ Nutrient agar+ blood= Blood agar
◦ Blood agar+ heat= chocolate agar
 Selective media:
◦ Solid media which contain substances that inhibit the growth of
some bacteria and letting the others grow.

15.  Enrichment media:
◦ These are liquid media that are similar in function to ...
◦ The only difference is that…
 Differential media:
◦ Contains indicators that will differentiate one organism
from another
 Transport media:
◦ Contain substances that can prevent overgrowth of
commensals and prevent bacteria from dying as a result
of change in pH or enzyme action.

16.  Media should be tested for:
1. Sterility.
2. Each medium must be tested with organisms expected
to grow or give a positive reaction as well as with
organisms expected not to grow.

18. But when we’ll go over it, it’ll
The media looks like this… look like this ;)

20. Liquid Sample (or Broth) Swab
An agar

24.  Temperature.
 Hydrogen ion concentration (pH).
 Gaseous requirements.

25.  Too high temperature will denature bacterial
ezymes. While too low temperature….
 Types of bacteria according to their growth
temperature:
1. Psychrophiles: bacteria that grow between 0-20oC.
2. Mesophiles: those that grow between 21oC and 50oC.
3. Thermophiles: the ones that grow between 50oC and
100oC.

26.  Acidophiles: bacteria that grow in acidic pH.
 Neutrophiles: those that grow in between 4-9.
 Alkalophiles: ones that grow in alkaline pH.

27. Bacteria differ in their need to molecular oxygen for
growth:
 Obligatory (strict)aerobes: require free oxygen for
growth.
 Obligatory (strict) anaerobes: grow only in the
absence of free oxygen.
 Facultative anaerobes: multiply either in the
presence or absence of free oxygen.
 Carboxyphilic (capnophilic): these bacteria require
raised level of carbon dioxide (5-10%).