the streak-stab technique, used to promote streptolysin activity, is preferred over incubating the plates anaerobically. Why do you think this is so? Compare and contrast what you see as the advantages and disadvantages of each procedure.

The streak-stab technique reduces oxygen (not completely eliminate it) and allows Streptococcus grow optimally than in a completely anaerobic environment.

Explanation:

Streptolysin is a haemolytic toxin produced by Streptococcus. Streptococcus is a facultative anaerobe, meaning it can grow in the presence or absence of air. However it grows optimally in a micro-anaerobic condition or in 5% CO2.

There are two types of streptolysin produced by Streptococcus - streptolysin O and S. O is oxygen labile (it cannot withstand oxygen) while S is oxygen stable.

O is also produced when the organism is actively growing or near the stationary phase of growth, while S is produced during the stationary phase. To detect the production of streptolysin by the organism on the agar plate, the organism has to be grown at optimum conditions. The streak stab method reduces the level of oxygen, thus providing a condition for the organism to grow maximally.