Table 1.2.

Contrasting Properties of Unicellular Microorganisms and Viruses

Property	Bacteria	Rickettsiae	Mycoplasma	Chlamydiae	Viruses
>300 nm diametera	Yes	Yes	Yes	Yes	No
Growth on non-living mediab	Yes	No	Yes	No	No
Binary fission	Yes	Yes	Yes	Yes	No
Contain both DNA and RNA	Yes	Yes	Yes	Yes	Noc
Infectious nucleic acid	No	No	No	No	Many
Functional ribosomes	Yes	Yes	Yes	Yes	No
Sensitivity to antibiotics	Yes	Yes	Yes	Yes	Nod

^aSome mycoplasmas and chlamydiae are less than 300 nm in diameter, and mimiviruses and the other new “giant DNA viruses” are greater than 300 nm in diameter.

^bChlamydiae and most rickettsiae are obligate intracellular parasites.

^cA few viruses contain both types of nucleic acid, but one of these types acts as the main functional molecule and the other plays a minor role.

^dWith very few exceptions.