Subbacterial

They are used frequently for the separation of particles of sub-bacterial dimensions and for the study of the sizes of the particles of ultramicroscopic viruses, bacteriophage and colloids.

Diseases that have most stubbornly resisted medical control are those caused by the subbacterial Rickettsiae and viruses. Cause of many tropical diseases, these organisms are the smallest living things. They can exist only side living cells.

The broadening of bacteriology has opened up new horizons in the field of subbacterial forms and has resulted in the alteration of the name of the study of microorganisms from bacteriology to microbiology.