Bacterialculture

Introduction

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

What are bacteria?

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.

Bacterial division

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 species20 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 O2, CO2, water availability .

Bacterial growth

After n cycles : 2n bactéria

Bacterial growthFor example, Escherichia coli

G= 20 minutes After 1 hour: 3 cycles : n = 23 = 8 bacteria After 2 hours: 6 cycles : n = 26 = 64 bacteria After 3 hours : 9 cycles : n = 29 = 512 bacteria After 4 hours : 12 cycles: n = 212 = 4096 bacteria After 5 hours : 15 cycles: n = 215 = 32768 bacteria … After 10 hours : 30 cycles : n = 230 = 1073741824 bacteria

More than a billion bacteriaafter 10 hours of culture!

Bacterial growth In liquid culture media :

Clear media

After 16h of culture =

turbid media

Increasing the cell density during the growth

Bacteria

Bacterial growth In solid culture media :

Accumulation of cells during the growth

After 16 - 24h : 1 bacteria 1 visible bacterial

colonyBacteria

Bacterialculture

Different culture media

Different cuture media Solid by adding a

gelling agent (agar) to a liquid media

Liquid

Different culture media depending on their useThe 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

Different culture media depending on their useDifferent packaging of identification

media

Agar plate media

Tubes media

Classics tubes

Multi-test miniaturized

systems