Question

Differentiate between direct and indirect methods for determination of cell concentration.

Answer 1

Methods to determine cell concentration

1. DIRECT METHOD: It is a direct method to measure the actual mass of a compound in a certain mass of microsphere.

2. INDIRECT METHOD: It is an indirect method to determine cell concentration in which the total mass of the compound is given and you have prepared the sample and measure the unencapsulated and subtract this value from the total amount used.

Methods - Measurement of cell concentration

1. Direct methods for cell concentration

• In this method, cells concentration can be directly measured by direct viable cell count technique.
• The pour plate and spread plate methods are widely used to determine the concentration of the cell that used the plate serial dilutions technique for counting viable cells that give rise to colony-forming units.
• Membrane filtration is another technique widely used to count live cells in dilute solutions.
• The most probable cell number (MPN )method is used to estimate the cell numbers in cultures without using solid media.

2. Indirect methods for cell concentration

• In indirect methods, culture density can be determined by measuring the turbidity of a culture or live cell density also can be done by measuring metabolic activity. Turbidometry is used to measure turbidity.
• Measuring the dry weight of a culture sample is widely used indirect method. In this method, the cell suspension is concentrated by filtration or centrifugation, washed, and later dried and then the mass is measured.
• In spectrophotometry method of the indirect cell concentration,  cultures are generally not diluted and the cell density is measured.