Microbes vs. Viruses

Explore the key differences between microbes and viruses, including size, structure and growth.

What Are Microbes?

Microbes generally refer to a class of “micro-scale” organisms where individual organism entities are too small to be seen by the naked eye. The study of microbes is called microbiology. Examples of microbes include bacteria, fungi, algae, and protozoa.

It is arguable if a virus is to be properly considered a microbe as, unlike a living organism, it does not have many of the vital features of living cells. Rather, a virus relies on its ability to hijack (or infect) other living cells to replicate itself using vital contents and features of the host cell. However, for purposes of simplicity, the definition of microbes can be broadened to include viruses.

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How Do Viruses Differ from Other Microbes?

Bacterial and fungal cells differ from viruses primarily in terms of their size and how they multiply. Viruses are 10-100 times smaller than bacteria and fungi. Viruses reproduce by infecting a living host cell and then multiplying in great numbers and can cause serious illness. Bacteria and fungi can multiply on inanimate surfaces (e.g., polymers, coatings, textiles). When bacteria and fungi cause infections, the illness is usually restricted to a local infection that affects a specific part of the human body.

CharacteristicBacteriaFungi (Molds and Yeasts)Viruses
Size0.15 – 2.0 µmMolds 10 – 40 µm
Yeasts 5 – 8 µm
0.02 – 0.3 µm
StructureMade of living cellsMade of living cellsMade of noncellular particles
Nucleic AcidBoth DNA and RNABoth DNA and RNAEither DNA or RNA
ProteinPresentPresentPresent
MembranesPresentPresentAbsent from non-enveloped viruses, present on enveloped viruses
Growth (Increase in Size)PresentPresentAbsent
Self-Multiplication (Increase in Number)YesYesNo – needs to be inside a host cell, such as animal cells, to use resources for multiplication
MetabolismYesYesNo
BeneficialYes: environmental nutrient cycling, food productionYes: environmental nutrient cycling, food production

No: viruses can infect humans, animals, plants, fungi, algae, protozoa, and bacterial cells


Used in research
Disease TreatmentAntibioticsAntibioticsAntiviral and symptom management



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