Question

In microbiology, what is the recommended procedure for determining the concentration of Lactobacillus delbruckii subsp lactis after 24 hours of growth in MRS broth?

a. Measure optical density at 600nm using a spectrophotometer
b. Conduct spread plating on MRS agar
c. Count colonies under a microscope
d. Perform PCR analysis for quantification

If Lactobacillus delbruckii subsp lactis does not grow well on MRS agar, what alternative method can be employed to estimate its concentration without spread plating?
a. Fluorescence microscopy
b. Turbidity measurement at 600nm
c. Gas chromatography
d. Polymerase chain reaction (PCR) quantification

Answer 1

Therefore the correct answer is option is a) Measure optical density at 600nm using a spectrophotometer

Therefore the correct answer is option is b) Turbidity measurement at 600nm

Step-by-step explanation:

The recommended procedure for determining the concentration of Lactobacillus delbruckii subspecies lactis after 24 hours of growth in MRS broth is to measure the optical density at 600nm using a spectrophotometer (option a).

This method allows for a quick and reliable estimation of cell concentration based on the absorbance of light by the bacterial suspension.

It is a common technique used in microbiology to quantify bacteria.

If Lactobacillus delbruckii subspecies lactis does not grow well on MRS agar, an alternative method to estimate its concentration without spread plating is to measure the turbidity at 600nm (option b).

Turbidity is a measure of cloudiness in a bacterial suspension and it correlates with the cell density.

Therefore, by measuring turbidity, one can indirectly assess the concentration of the bacteria.