History of Microbiology Practice Exam

Filtration experiments show that some infectious agents are smaller than bacteria, because a porous filter can trap bacteria but still allow smaller particles to pass through. The Chamberland filter, a porcelain device with very fine pores, demonstrated this by blocking bacteria yet letting certain infectious agents pass and still cause disease in a recipient. This showed there are pathogens smaller than bacteria and that they are filterable, which helped establish the idea of viruses. The other tools are not built around demonstrating this specific property: a Petri dish is for growing cultures, the Koch funnel isn’t the classic filtration demonstration used to reveal filterable agents, and a Pasteur pipette is for transferring liquids.