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.
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.
|Characteristic||Bacteria||Fungi (Molds and Yeasts)||Viruses|
|Size||0.15 – 2.0 µm||Molds 10 – 40 µm|
Yeasts 5 – 8 µm
|0.02 – 0.3 µm|
|Structure||Made of living cells||Made of living cells||Made of noncellular particles|
|Nucleic Acid||Both DNA and RNA||Both DNA and RNA||Either DNA or RNA|
|Membranes||Present||Present||Absent from non-enveloped viruses, present on enveloped viruses|
|Growth (Increase in Size)||Present||Present||Absent|
|Self-Multiplication (Increase in Number)||Yes||Yes||No – needs to be inside a host cell, such as animal cells, to use resources for multiplication|
|Beneficial||Yes: environmental nutrient cycling, food production||Yes: environmental nutrient cycling, food production|
No: viruses can infect humans, animals, plants, fungi, algae, protozoa, and bacterial cells
Used in research
|Disease Treatment||Antibiotics||Antibiotics||Antiviral and symptom management|