Question

The shape of Streptococcus thermophilus is____
A) Rod
B) Spherical
C) Curved
D) Spinal

Answer 1

Hint: Streptococcus thermophilus commonly known as lactic acid bacterium is a gram positive, facultative anaerobic bacteria that belong to the phylum Firmicutes. It was first isolated from yogurt in the year of 1974.

Complete answer:
Streptococcus thermophilus is non-motile, spherical in shape, does not produce any spore and is found in chains of various sizes with an optimum growth temperature ranging from 35 degree centigrade to 42 degree centigrade. Being a facultative anaerobe, they are capable of producing ATP for energy through both aerobic respiration as well as fermentation depending on the presence or absence of oxygen in the environment.

The cell wall of Streptococcus thermophilus is composed of N-acetylmuramic acid and N-acetylglucosamine that are linked by ether bonds. This structure helps the bacteria to survive high temperatures required during the fermentation of the milk. Streptococcus thermophilus has gained importance in industry not only because of its ability to ferment milk but also produces certain enzymes such as aminopeptidases that are used in food fermentation processes as starter cultures. It is also important as it is not affected by bacteriophages and is known to provide a consistent flavour and texture to the fermented dairy products.

So the correct answer is option (B) Spherical.

Note: Although Streptococcus thermophilus serves as a non-pathogen in the fermentation industry but it can act as a pathogen under certain conditions such as compromised immune system, heart valve disease, premature infants, central venous catheters causing adverse effects in them.