AH Biology - Unit 1 - KA1(f) - Aseptic Techniques and Cell Culture

What are aseptic techniques used to eliminate?

Aseptic techniques are used to eliminate unwanted microbial contaminants when culturing microorganisms or cells.

What do aseptic techniques involve?

Aseptic techniques involve the sterilisation of equipment and culture media by heat or chemical means and the exclusion of microbial contaminants after this.

How are microbial cultures started?

Microbial cultures are started by using an inoculum of microbial cells. These are cultured on either an agar medium or in a broth containing suitable nutrients.

What are there lots of different types of that promote the growth of specific cell types and/or microbes?

There are lots of different culture media that promote the growth of specific cell types and/or microbes.

What do animal cells need to be cultured in?

Animal cells need to be cultured in a medium containing growth factors from serum. Growth factors are proteins that promote cell growth and proliferation (cell division).

In animal cell cultures, what can primary cell lines do?

In animal cell cultures, primary cell lines (cells cultured directly from cells in a tissue) can only divide a limited number of times.

What lines of cells are often used instead of primary cell lines?

Often, tumour cell lines are used instead of primary cell lines because they can divide an unlimited number of times.

What are the two ways microbial culture cell density estimates can be done?

The two ways microbial culture cell density estimates can be done are:

• Plating out and serial dilutions

• Haemocytometers and vital staining

What can liquid microbial cultures be plated out to do?

Liquid microbial cultures can be plated out (grown on agar plates) and the number of colony-forming units can be counted to estimate the density of cells in the culture.

What often occurs when liquid microbial cultures are plated out and grown to estimate the density of cells in the culture?

When liquid microbial cultures are plated out and grown to estimate the density of cells in the culture, the cultures are often too dense and a serial dilution of the liquid culture must be carried out first to achieve a suitable density for a colony count. add pic

What are haemocytometers, and what can be calculated from this?

Haemocytometers are a special type of slide used to estimate cell numbers/density in a liquid culture. They have a grid and can be filled with a known volume of culture. From this, the number of cells in a known volume can be easily counted and the estimated population density can be calculated.

What is a viable cell count?

A viable cell count is where only the living (viable) cells are counted.

To carry out a viable cell count, what must be done first?

To carry out a viable cell count, the sample must first be stained with a vital stain. Vital staining generally only stains the dead cells (as living cells contain working enzymes that break down the stain).