Laboratory Techniques For Biologists: Asceptic Techniques and Cell Culture

Question 1

Asceptic Technique

Answer 1

Asceptic technique eliminates unwanted microbial contamination when culturing micro-organisms or cells.

Asceptic technique involves the sterilisation of equipment and culture media by heat or chemical means and subsequent exclusion of microbial contaminants.

Question 2

Microbial culture

Answer 2

A microbial culture can be started using an inoculum of microbial cells on an agar medium, or in a broth with suitable nutrients.

Many culture media exist that promote the growth if specific types of cells and microbes

Question 3

Animal cell culture

Answer 3

Animal cells are grown in medium containing growth factors from serum.

(growth factors are proteins that promote cell growth and proliferation, growth factors are essential for the culture of most animal cells)

Question 4

Counting colony-forming units

Answer 4

Planting out a liquid microbial culture on solid media allows the number of colony-forming units to be counted and the density of cells in the culture estimated.

Serial dilution is often needed to achieve a suitable colony count

Question 5

Using haemocytometers

Answer 5

A heamocytometer is a graduated microscope slide used to count cell density.

The cover slip of a haemocytometer slide is deigned to sit a known distance from the slide. This means that the viewer is looking through a known volume of medium. By counting the number of cells in a particular area of the grid, a cell density can be calculated.

A haemocytometer can be used to make total cell counts, or if vital staining is used to distinguish living cells, it can be used to make viable cell counts.