McDonald's Interview Questions and Answers

Gram staining is used to differentiate between gram negative and gram positive bacteria based on their cell wall composition.

• Gram staining is a common technique used to differentiate between gram negative and gram positive bacteria.

• Gram positive bacteria retain the crystal violet stain and appear purple under a microscope.

• Gram negative bacteria do not retain the crystal violet stain and appear pink or red under a microscope.

• The key difference between them is the composition o...read more

RVSEB medium is prepared by autoclaving the components at 121°C and 15 psi pressure.

• RVSEB medium is prepared by mixing the components including peptone, yeast extract, sodium chloride, and agar in appropriate proportions.

• The mixture is then sterilized by autoclaving at 121°C and 15 psi pressure for about 15-20 minutes.

• After autoclaving, the medium is cooled down to around 50°C before pouring into plates or tubes for solidification.

The pH of SCDA & SDA media after sterilization should be around 5.6 to 6.8.

• The pH of SCDA & SDA media is important for the growth of fungi.

• The pH range should be maintained between 5.6 to 6.8 for optimal fungal growth.

• Deviation from the optimal pH range can affect the growth of fungi and the results of the culture.

• pH can be adjusted using acid or base solutions before sterilization.

• Monitoring pH post-sterilization ensures the media is suitable for fungal culture.

Indicator tape changes color when exposed to high temperature during sterilization process. Chemical present is usually lead acetate.

• Indicator tape changes color when exposed to high temperature during sterilization process

• Chemical present on indicator tape is usually lead acetate

• Indicator tape is placed on the outside of the packaging to show that the contents have been sterilized

Nutrient agar is suitable for growth of E.coli due to its rich nutrient content.

• Nutrient agar is a common media used for cultivating E.coli.

• It contains all the necessary nutrients for E.coli growth.

• Other suitable media include LB agar and MacConkey agar.

XLDA media is prepared at 42°C.

• XLDA media is prepared at a temperature of 42°C.

• The temperature is crucial for the growth of specific bacteria in the media.

• Maintaining the correct temperature is important for the success of the culture.

Spectrophotometer principle is based on measuring the amount of light absorbed or transmitted by a sample at different wavelengths.

• Spectrophotometer measures the amount of light absorbed or transmitted by a sample at different wavelengths.

• It uses a light source, a monochromator to select specific wavelengths, a sample holder, and a detector to measure the intensity of light.

• The principle is based on Beer-Lambert Law, which states that absorbance is directly proportional to th...read more