Bacterial culture

Click here to load reader

  • date post

  • Category


  • view

  • download


Embed Size (px)


Bacterial culture. 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. - PowerPoint PPT Presentation

Transcript of Bacterial culture

Diapositive 1

BacterialcultureIntroductionWhat are bacteria? Prokaryotic organismUnicellular No nuclear envelope around the genomic DNAAbsence of cellular organites 1-10 m Variable shapes (round, stick ...) May be pathogenic

What are bacteria?

Bacterial divisionMultiplication 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 growthGrowth 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 bactriaBacterial growthFor example, Escherichia coliG= 20 minutes

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

More than a billion bacteriaafter 10 hours of culture!Bacterial growthIn liquid culture media :

Clear media

After 16h of culture = turbid mediaIncreasing the cell density during the growthBacteriaBacterial growthIn solid culture media :Accumulation of cells during the growth

After 16 - 24h : 1 bacteria 1 visible bacterial colonyBacteriaBacterialcultureDifferent culture mediaDifferent cuture mediaSolid by adding a gelling agent (agar) to a liquid media


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 mediaTubes mediaClassics tubes

Multi-test miniaturized systems