| | Microbiology encompasses the study of microorganisms, such as bacteria, viruses, fungi, and protozoa. |
| Viruses are acellular organisms that comprise a nucleic acid genome enclosed in a protein capsid. Viruses cannot reproduce on their own, but must infect a host cell and use the host metabolic machinery to form progeny virions.
Viruses challenge the definition of life, because they do not move, grow, or breathe. It appears that their only function is to replicate.
Viruses have been implicated in numerous diseases, including AIDS (Acquired Immune Deficiency Syndrome) and the common cold. |
| Bacteria are single-celled microorganisms that lack nuclear membranes. Their genetic material are encoded in the form of DNA.
Bacteria can exist everywhere, including the geothermal springs originally thought to not harbor living organisms. Bacteria are widely known to be harmful through the diseases they cause, but some forms of bacteria are either harmless and even helpful. Bacteria that populate the intestinal canals can aid in digestion, while others can be harnessed to mass produce certain genes for diverse scientific applications. |
| The Koch's Postulates were developed by Robert Koch (1843-1910) to determine whether a particular microbial organism is the causative agent of a specific disease. The criteria are as follow:
1) The pathogen must be present in the host in every case of the disease;
2) The pathogen must be isolated from the host and grown in a culture;
3) Inoculation of the pathogen into a healthy host must cause the same disease; and
4) The pathogen must be reisolated from the infected host and demonstrated to be the same as the original pathogen. |
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