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Microbiology is the study of microorganisms, including unicellular (single-celled) eukaryotes and prokaryotes, fungi, and viruses. Today, most of the work in microbiology is done using methods from biochemistry and genetics. It is also related to pathology, immunology, and epidemiology as many microorganisms are pathogens.Microbiologists have made many fundamental contributions to biology, especially in the fields of biochemistry, genetics, and cell biology. Microbes have many traits that make them ideal model organisms:
- They are small, therefore they do not consume many resources
- Some have very short generation times (~30 minutes for E. coli)
- Cells can easily survive in isolation from other cells
- They can reproduce by mitoticIn biology, mitosis is the process of chromosome segregation and nuclear division that follows replication of the genetic material in eukaryotic cells. This process assures that each daughter nucleus receives a complete copy of the organism's genome. division, allowing for the propagation of genetically identical ( clonalThe term clone is derived from kappa;λω&nu the Greek word for "twig". In horticulture, the spelling clon was used until the twentieth century. The final e came into use to indicate the vowel is a "long o" instead of a "short o"; see the refer) populations.
- They may be frozen for long periods of time. Even if 90% of the cells are killed by the freezing process, there are millions of cells in a milliliter of liquid culture.
These traits allowed Joshua and Esther Lederberg to devise an elegant experiment in 1951Events January events January 9 United Nations headquarters officially opens ( New York City). January 15 Ilse Koch, The "Witch of Buchenwald," wife of the commandant of the Buchenwald concentration camp, is sentenced to life imprisonment in a court in We demonstrating that adaptive mutations arise from preadaptation rather than directed mutation. For this purpose, they invented replica platingReplica plating is a technique in which multiple dishes, also known as Petri plates, containing solid ( agar-based) microbial media, are inoculated with between thirty and three-hundred colonies of microorganisms from a primary plate (or master dish), rep, which allowed them to transfer numerous bacterial coloniesIn biology, a colony (from Latin colonia means several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defences, the ability to attack bigger prey etc. Some insects ( ants, for example) live o from their specific locations on one agar-filled petri dish to analogous locations on several other petri dishes. After replicating a plate of E. coli, they exposed each of the new plates to phageA phage (also called bacteriophage is a small virus that infects only bacteria. Like viruses that infect eukaryotes, phages consist of an outer protein hull and the enclosed genetic material (which consists of double-stranded DNA in 95% of the phages know. They observed that phage-resistant colonies were present at analogous locations on each of the plates, allowing them to conclude that the phage resistance trait had existed in the original colony, which had never been exposed to phage, instead of arising after the bacteria had been exposed to the virus.
The extensive characterization of microbes has allowed them to be used as tools in other branches of biology:
- Bacteria (especially E. coli) may be used to replicate DNADeoxyribonucleic acid DNA is a nucleic acid which carries genetic instructions for the biological development of all cellular forms of life and many viruses. DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate in the form of a plasmidPlasmids are (typically) circular double stranded DNA molecules that are separate from the chromosomal DNA (Fig. They usually occur in bacteria, sometimes in eukaryotic organisms (e. the 2-micrometre-ring in Saccharomyces cerevisiae . Their size varies fr. This DNA is often chemically modified in vitro then inserted into bacteria to select for the desired traits and isolate the desired product from by-products of the reaction. After growing the bacteria and thereby replicating the DNA, the DNA may be further modified and inserted into other organisms.
- Bacteria may be used to produce large amounts of protein using genes encoded on a plasmid.
- Bacterial genes have been inserted into other organisms as reporter genes.
- The yeast two-hybrid system combines bacterial genes with genes from the organism being studied and inserts them into yeast cells to study protein-protein interactions within a cellular environment.
- See also Immunology -- Virology -- Archaea -- Genetics -- Biochemistry -- Geomicrobiology -- Important publications in microbiology
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