They differ in terms of size , shape , nutrition and many more

They differ in terms of size , shape , nutrition and many more.

are different from all other infectious microorganisms because they are the only group of microorganisms that cannot replicate outside of a host cell. Because viruses do not eat food - instead they seize materials and energy from host cells by hijacking cellular machinery .Some viruses, called bacteriophages, even infect .

Bacteria are ten to 100 times larger than viruses. They are typically 1 to 3 microns in length and take the shape of a sphere or rod. Some bacteria live and multiply in the environment while others are adapted to life within human or animal hosts. Some bacteria can double in number every fifteen minutes while others take weeks or months to multiply.

Parasites are usually larger than bacteria, although some environmentally resistant forms are nearly as small. Some parasites only replicate within a host organism, but some can multiply freely in the environment. Fungi are diverse in terms of their shape, size and means of infecting humans. Fungi are eukaryotes, meaning that like parasites, their cells have a true nucleus and complex internal structures.