Lecture 13

Question 1

How does Defined Substrate Technology (DST) work?

Answer 1

DST uses specific nutrients and indicators to detect the presence of target microorganisms. For example, in the 3M Petrifilm E. coli Count Plate, Violet Red Bile nutrients encourage the growth of coliforms, a cold water-soluble gelling agent, and an indicator help identify E. coli. TTC enhances visibility.

Question 2

What is the principle of DST and how does it detect microorganisms (MOs)?

Answer 2

DST identifies microorganisms based on their unique enzymatic activities and their ability to utilize specific substrates.

Selective Media: Encourages the growth of target microorganisms while inhibiting others.
Specific Substrates: Substrates like lactose in the media are metabolized by target microorganisms.
Indicator Reactions: Changes in colour or fluorescence indicate enzymatic activity.
Gas Production: Some DST methods detect gas production as a byproduct of microbial metabolism.