Question

Which of the following is a unicellular fungus?
A. Yeast
B. Mucor
C. Acetabularia
D. E. coli

Answer 1

An organism characterised by the presence of glucans (beta glucans), mannoproteins and chitin, primarily composed of cell walls. It is used as a leavening agent in baking, where the food / fermentable sugars present in the dough are converted into the gas carbon dioxide.

Complete answer:
Option A is correct. Yeast (Saccharomyces cerevisiae), is a single-cell, eukaryotic organism that requires food, warmth, and moisture to survive via fermentation, it converts the food-sugar and starch- into carbon dioxide and alcohol. This is the carbon dioxide that triggers the growth of baked goods. It is used as a leavening agent in baking, where the food/fermentable sugars present in the dough are converted into the gas carbon dioxide. When gas forms pockets or bubbles, this causes the dough to expand or grow.
Option B is incorrect. Mucor is present in soil, seeds, rotting fruits and vegetables as a filamentous fungus. Mucor genus as well as being omnipresent in nature and a common laboratory contaminant, humans, frogs, amphibians, cattle, and pigs can cause infections. Most of the Mucor species are unable to grow at 37 degree Celsius and one of the few thermotolerant Mucor species is typically the strains isolated from human infections.
Option C is incorrect. Acetabularia is a single-celled organism and a genus of green algae in the Polyphysaceae family, usually found in subtropical waters, but gigantic in size and complex in shape, making it an ideal model organism for studying cell biology. Acetabularia is a single-celled organism. Acetabularia, also called the wine glass of the mermaid, is one of the largest single-celled species and has an exceptionally large nucleus as well.
Option D is incorrect. Escherichia coli, also referred to as E. Coli is a single-celled, gram-negative, optionally anaerobic, rod-shaped, coliform bacteria of the genus Escherichia, commonly found in warm-blooded organisms in the lower intestine. Most of the E. coli strains are harmless, but certain serotypes can cause severe food poisoning in their hosts and are often responsible for outbreaks of food contamination that trigger product recalls.

So, the correct answer is Option A.

Note: With a wide range of ecosystems, yeast is extensively distributed in nature. They are typically present in leaves, bulbs, and fruits of plants, as well as in soil. Yeast is also present on the surface of the skin and in warm-blooded animals' intestinal tracts, where they can reside symbiotically or as parasites.