Question

1. What is a sterile technique and why is it so important in animal cell culture?

2. Explain the rationale for adding pen/strep to DMEM?

3. What is the difference between an inverted and upright light microscope? Gibe an example of when you would use either?

Answer 1

1) Sterile technique means keeping the cells free from contamination by microorganisms such as bacterial, fungi, and viruses.

It is used to proved barrier between the microorganisms in the environment and the sterile cell culture, depends upon a set of procedures to reduce the probability of contamination from these source.

2) The penicillin or steptomycin is added into DMEM because of long history of using these antibiotics and we'll characterized effect in almost all cell culture.

3) upright microscope move stage for focusing ( unless fixed stage and inverted move objective for focusing.

Upright the optical path is simpler and inverted better access for live cells in culture.

Upright is easier for immersion ( long working distance) and inverted harder for oil, water immersion.

Examples: upright microscope is used for phase contrast or widefield fluorescence microscopy of living cells or samples that are squeezed between a slide and coverslip, the material which are sterile are examined under inverted microscope.