Question

Which microorganisms can be cultivated in artificial laboratory media without living cells ?
A. Bacteria
B. Viruses
C. Fungi : yeasts
D. Fungi : molds
E. Protozoa

• A. A, B, C Only
• B. A, C, D Only
• C. A, C, D and E Only
• D. A, B, D and E Only

Hint:

The most important rule in introductory microbiology: Viruses cannot grow on agar! They are essentially just genetic material wrapped in a protein coat; they need a living factory to copy themselves.

Answer 1

The Correct Option is B

Step 1: Concept:
This question tests basic microbiology, specifically distinguishing between free-living microbes that can synthesize their own requirements from chemical nutrients versus obligate intracellular parasites that completely rely on a living host cell machinery to replicate.

Step 2: Step-by-step Explanation:

• Artificial cell-free media (like nutrient agar, blood agar, or broth) contain various chemical nutrients, amino acids, and sugars, but absolutely no living host cells.

• A. Bacteria: The vast majority of bacteria are free-living and easily cultivated on standard artificial media (with rare exceptions like Chlamydia or Rickettsia).

• B. Viruses: Viruses are strictly obligate intracellular parasites. They lack their own metabolic machinery and ribosomes, meaning they cannot synthesize proteins or replicate without hijacking a living host cell (like a tissue culture or embryonated egg). They can never be cultivated on cell-free artificial media.

• C & D. Fungi (yeasts and molds): Fungi are completely free-living, eukaryotic organisms. They grow exceptionally well on specialized cell-free artificial media, such as Sabouraud Dextrose Agar (SDA).

• E. Protozoa: While some advanced techniques (axenic cultivation) exist for certain protozoa (like Entamoeba), many medically important protozoa (like Plasmodium causing malaria) strictly require living host cells (like red blood cells). Because of this strict requirement for many clinical species, they are generally excluded in classic textbook definitions of routine cell-free cultivation alongside bacteria and fungi.

• Therefore, Bacteria, Yeasts, and Molds are the classic group routinely grown on cell-free artificial media.

Step 3: Final Answer:
The correct combination is A, C, and D Only.