1. Bacterial culture Introduction

2. What are bacteria?  Prokaryotic organism  Unicellular  No nuclear envelope around the genomic DNA  Absence of cellular organites  1-10 μm  Variable shapes (round, stick...)  May be pathogenic

3. What are bacteria?

4. Bacterial division  Multiplication by binary fission: the bacteria grows and divides into two identical daughter cells.  Preceded by duplication of the bacterial chromosome with the DNA replication.  Various synthesis and degradation enzymatic systems involved in the cell division.

5. Bacterial division

6. Bacterial growth  Growth of all the components of the bacteria which leads to increasing the number of bacteria  Characterized by a generation time (G) variable depending on the species 20 minutes for Escherichia coli, Lactobacillus acidophilus for 100 minutes, 1000 minutes to Mycobacterium tuberculosis  Depends on physical and chemical parameters such as pH, temperature, the presence of O 2, CO 2, water availability.

7. Bacterial growth After n cycles : 2 n bactéria

8. Bacterial growth For example, Escherichia coli G= 20 minutes  After 1 hour: 3 cycles : n = 2 3 = 8 bacteria  After 2 hours: 6 cycles : n = 2 6 = 64 bacteria  After 3 hours : 9 cycles : n = 2 9 = 512 bacteria  After 4 hours : 12 cycles: n = 2 12 = 4096 bacteria  After 5 hours : 15 cycles: n = 2 15 = 32768 bacteria ……  After 10 hours : 30 cycles : n = 2 30 = 1073741824 bacteria More than a billion bacteria after 10 hours of culture!

9. Bacterial growth  In liquid culture media : Clear media After 16h of culture = turbid media Increasing the cell density during the growth Bacteria

10. Bacterial growth  In solid culture media : Accumulation of cells during the growth After 16 - 24h : 1 bacteria  1 visible bacterial colony Bacteria

11. Bacterial culture Different culture media

12. Different cuture media  Solid  Solid by adding a gelling agent (agar) to a liquid media  Liquid

13. Different culture media depending on their use The isolation and identificationmedia The isolation and identification media Selective media = Contains a selective agent promoting the culture of an exclusive family of microorganism Identification media = Used to characterize bacteria with differential colorimetric tests Basal media = all common bacteria culture

14. Different culture media depending on their use Different packaging of identification media Agar plate media Tubes media Classics tubes Multi-test miniaturized systems