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Bacterial taxonomy is the classification of strains within the domain Bacteria into hierarchies of similarity. This classification is similar to that of plants , mammals , and other taxonomies. However, biologists specializing in different areas have developed differing taxonomic conventions over time.
Even within one species, different strains have different transformation efficiencies, sometimes different by three orders of magnitude. For instance, when S. cerevisiae strains were transformed with 10 ug of plasmid YEp13, the strain DKD-5D-H yielded between 550 and 3115 colonies while strain OS1 yielded fewer than five colonies. [54]
A strain is a genetic variant or subtype of a microorganism (e.g., a virus, bacterium or fungus). For example, a "flu strain" is a certain biological form of the influenza or "flu" virus. These flu strains are characterized by their differing isoforms of surface proteins.
Pneumonia was a serious cause of death in the wake of the post-WWI Spanish influenza pandemic, and Griffith was studying the possibility of creating a vaccine. Griffith used two strains of pneumococcus (Diplococcus pneumoniae) bacteria which infect mice – a type III-S (smooth) which was virulent, and a type II-R (rough) strain which was ...
Mutation rates vary widely among different species of bacteria and even among different clones of a single species of bacteria. [136] Genetic changes in bacterial genomes emerge from either random mutation during replication or "stress-directed mutation", where genes involved in a particular growth-limiting process have an increased mutation rate.
This process is thought to be a significant cause of increased drug resistance [5] [54] when one bacterial cell acquires resistance, and the resistance genes are transferred to the other species. [ 55 ] [ 56 ] Transposition and horizontal gene transfer, along with strong natural selective forces have led to multi-drug resistant strains of S ...
Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of the mechanisms of antigenic escape.
Many bacterial species can utilize inversion to change the expression of certain genes for the benefit of the bacterium during infection. [1] The inversion event can be simple by involving the toggle in expression of one gene, like E. coli pilin expression, or more complicated by involving multiple genes in the expression of multiple types of ...