Question

The first clear cut evidence of a virus was given by

• A. Mayer
• B. Louis Pasteur
• C. Robert Koch
• D. Ivanovski

Hint:

To remember early virology milestones: Ivanovsky provided the first mechanical proof using filters, while Beijerinck named the fluid "contagium vivum fluidum."

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The foundational history of virology began in the late 19th century when researchers investigated unusual diseases that were not caused by standard culturable bacteria.
At the time, porcelain filters (such as the Chamberland filter) were used to trap all known bacterial cells from liquid extracts.

Step 2: Detailed Explanation:
Adolf Mayer in 1886 showed that tobacco mosaic disease was infectious by transferring sap between plants, but he believed the cause was a bacterium that could not be isolated.
Dmitri Ivanovsky in 1892 systematically tested this infectious sap by passing it through a Chamberland filter.
He discovered that the filtered sap remained fully capable of causing the disease in healthy tobacco plants, even though no bacteria could be cultured from the filtrate.
This experimental result provided the first clear, reproducible proof of a sub-microscopic, filterable infectious agent, which was later recognized as a virus.
Louis Pasteur made major contributions to vaccines, such as the rabies vaccine, but did not experimentally demonstrate a filter-passing agent.
Robert Koch established his famous postulates to identify specific bacterial pathogens, which were ineffective for viruses since they cannot be grown on cell-free media.

Step 3: Final Answer:
The experimental work of Dmitri Ivanovsky provided the first clear-cut demonstration of a filterable virus.