technique de labo Flashcards
Spread-plate method
- pipette
- spread the sample evenly over surface of agar
- Incubation
Pour-plate method
- Sample pipette into sterile plate
- Sterile medium added and mixed
- Solidification and incubation
What do u need for growth to happen?
permissive growth medium
When are results reliable ?
colonie btw 30-300
Serial dilution, bacterial culture can reach?
high humbers of cells
serial dilution, How to get viable count of such cultures?
serial dilutions have to be made
Seria dilution, the resulsts and reproducibility are strongly affected by?
the skills of the technician
CFU
number of colonie / dilution x volume plated
microscopic counts
use of special slides known as counting chambers
microscopic counts, tu dois faire attention a pas
overflow
microscopic counts, technique where u can?
count cells, dead , alive, and the one’s who can’t grow in lab
What can be used to differentiate dead from alive?
Variability staining
microscopic counts, what are the pros?
- Fast
- No need to wait until bacteria has grown (no incubation)
microscopic counts, cons?
- Small cells can be missed
- motile cells are hard to count and must be immobilized
What happen if a cell is on the line?
u count it but u don’t count the ones who are at the top or at the bottom
Flow cymetry
technology that is used to analyse the physical and chemical characteristics of particles in a fluid as it passes through at least one laser.
flow cymetry, is better at?
counting big cells
Big cells like ?
Protozoan,yeast,mammalian,cells
flow cymetry, what allows labeling of specific cell types or species
Detection of fluorescent dyes
Flow cymetry, en gros?
a chaque fois que passe une cellule le laser est interrompu et un signal est donner
flow cymetry, et quand une cellule par exemple stained passe?
le laser emet deux type de reflection , une reflextion stained et une reflexion normale
flow cymetry can be used to sort cells according?
size,shape,labeling
cons of Flow cytometry?
can be time consuming and expensive
Turbidimetric method
the process of measuring the loss of intensity of transmitted light due to the scattering effect of particles suspended in i
turbidity is measured with?
spectrophotometer
spectrophotomer?
an instrument that passes light through a cell suspension and measures the unscattered light that emerges
A spectrophotometer employs a?
prism or diffraction grating to generate incident light of a specific wavelength (
what happens in the spectrophotometer en ordre?
- Light
- Prism ( generate incident light )
- passes filter
- runs through the sample containing cells
- Photocell (measures unscattered light)
what is measured is?
the optical density ( log Io/I)
turbidity works until &
jusqu’a une certaine concentration
specto, measures both contribution of ?
both living and dead cells
OD is affected by?
properties of cells: size, clumping
If bacterias form aggregates?
can decrease the spectograph measurement
spectogram is viable btw ?
90.1 and 1
A standard curve must be made
and the relationship between OD
and cell number must be
established?
empirically
