Microbial Diversity: Acellular Microbes

Acellular Microbes/Infectious Particles

considered as non-living organism as they need a host in order for them to survive. (Ex. viruses, viroids, and prions)

Virions

Complete virus particles; very small and simple in structure.

Animal viruses

Viruses that infect humans and animals

Virus

microscopic organisms that can infect hosts, like humans, plants or animals. They're a small piece of genetic information (DNA or RNA) inside of a protective shell (capsid).

Virus

Possess either DNA or RNA

What viruses rely on for protein and nucleic acid production.

Ribosomes, enzymes, and metabolites (“building blocks”) of the host cell

Two or three parts of a Virion

Inner nucleic acid core, Protein coat (the capsid), lipid-containing envelope (In larger viruses).

All DNA viruses are double-stranded except

Parvovirus and Circovirus.

All RNA viruses are single-stranded except

Reovirus.

Mimivirus

extremely large double-stranded DNA virus; recovered from Amoebas; It “mimics” bacteria. It is so large that it can be observed using a standard compound light microscope.

Plant Viruses

More than 1,000 different viruses that causes plant diseases (ex. diseases of citrus trees, cocoa trees, etc.)

Viroid

infectious RNA molecules that cause a variety of plant diseases. (ex. potato spindle tuber, citrus exocortis, diseases of chrysanthemums, coconut palms, and tomatoes.)

Prions

infectious protein molecules that cause a variety of animal and human diseases 9 e.g. scrapie in sheep and goats; bovine spongiform encephalopathy (BSE); “mad cow disease” and kuru, Creutzfeldt-Jakob (CJ) disease, Gerstmann-Sträussler-Scheinker (GSS) disease, and fatal familial insomnia in humans.)

Kuru

a disease that was once common among natives in Papua, New Guinea; where women and children ate human brains as part of a traditional burial custom (ritualistic cannibalism). Diseases that are fatal spongiform encephalopathies; in which the brain becomes riddled with holes (sponge like).

Prions

Abnormal form of a cellular protein; No DNA or RNA; Consist only of Protein

Viroids

Obligated intracellular agents that can only replicate within the living cells of a host; Only have RNA; no protein coat

Viral Replication

1.     Attachment: of phage to cell surface receptor

2.     Penetration: of the entire virus into the host cell.

3.     Uncoating: where the viral nucleic acid escapes from the capsid.

4.     Biosynthesis: resulting in the production of pieces or parts of viruses.

5.     Assembly: to create complete virions.

6.     Release: of the complete virion from the host cell by lysis or budding.