1. Media!

5. Figure 1.16 Bacterial colonies on agar
Bacterium 6
Bacterium 7
Bacterium 5
Bacterium 8
Bacterium 4
Bacterium 9
Bacterium 3
Bacterium 10
Bacterium 2
Bacterium 11
Bacterium 1
Bacterium 12

6. Figure 6.8 Characteristics of bacterial colonies-overview

7. Figure 6.9 Streak plate method of isolation-overview

8. Culturing Microorganisms
Culture Media
Majority of prokaryotes have not been grown in culture medium
Six types of general culture media
Defined media
Complex media
Selective media
Differential media
Anaerobic media
Transport media
© 2012 Pearson Education Inc.

9. Figure 6.11 Slant tube containing solid media
Butt

10. Figure 6.13 The use of blood agar as a differential medium
Beta-hemolysis
Alpha-hemolysis
No hemolysis (gamme-hemolysis)

11. Figure 6.15 Use of MacConkey agar as a selective and differential medium-overview

12. Acid fermentation with gas
Figure The use of carbohydrate utilization tubes as differential media
Durham tube (inverted tube to trap gas)
No fermentation
Acid fermentation with gas

13. 3 Reasons why we inoculate differential and selective media
To culture all bacteria present and see which if any predominates.
To differentiate species by certain characteristic responses to media ingredients.
To selectively encourage growth of species of interest while suppressing normal flora.

14. Differential media - media that helps us separate bacteria based on a metabolic process (enzyme tests, carbohydrates)
Selective media – media that contains an ingredient that encourages the growth of some bacteria, but discourages the growth of other bacteria.

15. MSA – Mannitol Salt Agar, For isolation and differentiation
of Staphylococcus species
Differential – mannitol sugar Selective – 7.5% NaCl
Indicator – phenol red
Yellow = acidic = (+) for mannitol fermentation
Orange/red = neutral, no reaction
Hot pink = alkaline = (-) for mannitol fermentation

16. MacConkey Agar – used to isolate and differentiate gram negative organisms
Differential – lactose fermentation
Selective – bile salts and crytal violet
- pH Indicator: neutral red
         
Hot pink colonies =
(+) for lactose fermentation
 Colorless colonies =
(-) for lactose fermentation

17. Blood agar – Differential based on hemolysis,
isolation and cultivation of fastidious bacteria
Alpha – incomplete breakdown of hemoglobin;
Beta – complete breakdown of hemoglobin; clearing of medium;
Gamma or non-hemolytic; no hemolysins present; no change in medium Enterococcus faecalis

18. Starch Agar – to check for the presence of amylase via starch hydrolysis.
Reagent – Iodine; Bacillus sp.
Halo = (+) for Amylase
No Halo = (-) for Amylase

19. EMB – Eosin Methylene Blue Agar,
isolate Gram neg. bacteria
Selective – eosin; methylene blue; inhibitory to
Gram + organisms
Differential – lactose fermentation
Metallic green/blue black colonies- (+) vigorous lactose fermentors, acidic
Dark Purple – (+) slower fermentors
acidic
Light pink/colorless –
(-) not fermenting

20. Phenol Red Broths: used to determine carbohydrate fermentation with or without gas production (Durham tube);
tubes are read as:
A for acid (yellow);
NR for no reaction; and
K for alkaline (pink)
G for gas (trapped bubbles in the Durham tube);
(+) for carbohydrate fermentation
(-) for carbohydrate fermentation
Reversion – best to read tubes hours.

21. SIM tubes – sulfide, indole, motility
Hydrogen sulfide (H2S) production leads to blackening of medium
Black = (+) H2S No black = (-) H2S
Indole is a by-product of the breakdown of tryptophan
reagent: Kovac’s
Red = (+) for Indole
Yellow = (-) for indole
Motility – determined by
cloudiness away from the
stab line
Example of how to write
the reaction: S+ I+ M-