Who are the scientists associated with recognizing filterable infectious agents and shaping virology?

• A. Dmitri Ivanovsky and Martin Beijerinck
• B. Louis Pasteur and Robert Koch
• C. Howard Florey and Ernst Boris Chain
• D. Alexander Fleming and Howard Florey

Answer: (A)

This question asks about the scientists who first recognized filterable infectious agents and helped establish virology. Dmitri Ivanovsky showed that the agent causing tobacco mosaic disease could pass through a filter that trapped bacteria, implying there was an infectious agent smaller than bacteria. Martin Beijerinck built on that finding, naming the agent a virus and proposing the concept of a contagious living agent that could only replicate inside living cells, which laid the groundwork for virology as a field.

Other pairs in the options are known for different breakthroughs. Pasteur and Koch were pivotal in germ theory and bacteriology, studying bacteria rather than viruses. Fleming, Florey, and Chain are renowned for discovering and developing penicillin, the antibiotic, not for viruses. So the combination of Ivanovsky and Beijerinck best matches the question’s focus on filterable infectious agents and the birth of virology.