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Bacterial culture in laboratory. Introduction : bacterial growth.

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Presentation on theme: "Bacterial culture in laboratory. Introduction : bacterial growth."— Presentation transcript:

1 Bacterial culture in laboratory

2 Introduction : bacterial growth

3 Bacterial growth  Multiplication by binary fission: the bacteria grows and divides into two identical daughter cells.  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

4 Bacterial growth

5 After n cycles : 2 n bactéria

6 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 = bacteria ……  After 10 hours : 30 cycles : n = 2 30 = bacteria More than a billion bacteria after 10 hours of culture!

7 Bacterial culture in laboratory Culture media and inoculation technique

8 Culture media  Solid  Solid by adding a gelling agent (agar) to a liquid media  Liquid

9 Culture in liquid media Clear media After 16h of culture = turbid media Increasing the cell density during the growth Bacteria

10 Culture in solid media Accumulation of cells during the growth After h : 1 bacteria  1 visible bacterial colony Bacteria

11 Inoculation technique In liquid media :In solid media (usually with Agar Petri dish) : Spreading with a rake Ridges with a loop Ridges with a swab Inoculation with pipette Inoculation with loop

12 Bacterial culture in laboratory Aseptic conditions in lab

13 Bacteria to study… Problem 1 : Bacteria from environment can contaminate the preparation Problem 2 : Bacteria can contaminate the technician Problem 3 : Technician can contaminate the preparation Need a sterile zone around the preparation !!

14 Aseptic conditions in lab Equipment to create a sterile area to work… System which uses an HEPA filter (High Efficiency Particulate Air) to generate a flow of sterile air  Protection for the preparation and the technician Microbiological Safety Cabinet :

15 Aseptic conditions in lab Equipment to create a sterile area to work… Gas burner which delivers a flame at 1300°C  provides a sterile air zone near Bunsen Burner :

16 Aseptic conditions in lab Working with a Bunsen Burner : Convection air movement Sterile air area :  Approximately 40 cm diameter around the burner  This area is use to open tube or agar Petri dish with bacteria

17 Aseptic conditions in lab Organization of the workspace Bunsen Burner is place in the center of the workspace and all instruments are distributed around (aerial view) : Box with instruments (pipettes, inoculation loops…) Trash for contaminated instruments Rack tubes Agar Petri dish Bunsen Burner

18 Aseptic conditions in lab Organization of the workspace

19 Aseptic conditions in lab Consumables materials Most microbiology labs use sterile disposable equipment : Inoculation needles and loops Pipettes Volumetric pipettes Spreading rake


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