Question

Which of the following microorganisms are used in making Swiss cheese?
A. Propionibacterium
B. Geotrichum
C. Penicillium
D. Streptococcus

Answer 1

Hint: Swiss cheese is well known for its pockets of air, created during the culturing process. Swiss cheese has holes in them.

Complete answer: Propionibacterium: Propionibacterium is a gram-positive, anaerobic, rod-shaped genus of bacteria named for their unique metabolism.
They are able to synthesize propionic acid by using unusual transcarboxylase enzymes.
Swiss cheese is made by a bacterium Propionibacterium shermanii.
The large holes in this cheese are due to the production of a large amount of CO$_2$ by the bacterium.
Geotrichum: Geotrichum is a genus of fungi found worldwide in soil, water, air, and sewage, as well as in plants, cereals, and dairy products.
It is also commonly found in normal human flora and is isolated from sputum and feces.
Penicillium: Penicillium is a genus of ascomycetous fungi that is of major importance in the natural environment, in food spoilage, and drug production.
Some species are used to make antibiotics and some kind of cheese.
Streptococcus: Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria). Most of the species are pathogens while some are not pathogenic and are essential for dairy products.

So, the answer is A. Propionibacterium

Note: Propionibacterium are widely used in the production of vitamin B12.
It is commensal bacteria and sometimes causes infections known as acne vulgaris, caused by Cutibacterium acnes.