Question

You are given two tubes. one is a broth culture of Streptococcus pyogenes and the other is an agar slant of S. pyogenes. You prepare a smear and then simple stain each. Which smear do you expect to be denser?

Answer 1

Answer- Broth culture of Streptococcus pyogenes

Explanation-

1. Streptococcus pyogenes is grown in two different forms of culture medium- broth culture and agar slant. In this two culture forms different bacterial growth is observed.

2. In liquid broth culture bacterial growth is found to be denser when it's staining is done by smear preparation because in liquid media all nutrient components are dissolved completely and distributed evenly throughout media. Along with this surface are is greater than solid media so that bacterial cell will get exposed from all sides in liquid media. After cell division daughter cells also get maximum exposure to media components that lead to fast growth by maximum utilization of nutrients.

3. In contrast, on agar slant media organisms are only in contact with surface are where organisms are spreaded or streaked. In this as organisms grows, colonies are formed and daughter cells will get lower nutrients as compared to bacteria in contact with agar media. So that agar media which is not in contact with bacterial cells will remain unused and due to media unavailability growth rate decreases. When this culture is stained by smear preparation then growth will be less denser than broth culture media. Along with this S. pyogenes is aerotolerent so that it will grow maximally in liquid broth.

4. Smear prepared from liquid broth culture of S. pyogenes will be denser than smear prepared from agar slant.