Fact 1: Viruses often infect bacteria.

Fact 2: Viruses Viruses are the simplest organisms known.

Given the two facts above, answer the question "what often infects bacteria?" with the following options: 
- major threat to health
 - h2o
 - simplest known organisms
 - Food poisoning
 - mercury
 - humans
 - By wind and rain
 - microorganisms


 

   simplest known organisms      