Evolutionary Microbiology Essay
Introduction
Evolution has been a very controversial topic in terms of science and religion however with regard to prokaryotes there is no speculation about micro-organisms being able to evolve. In regard to micro-organisms the term evolution has a different meaning compared to eukaryotes. Prokaryote evolution refers to the adaptation of a micro-organism to the environment it exists in rather than the eukaryote evolution which states that the organism becomes a new species altogether. With prokaryotes there evolution can be analysed by many modern techniques that target the genome of the bacterium and compares it to other bacteria. However unlike eukaryotes that have fossil record that show species that existed millions of years ago,prokaryotes are not able to form fossils due to their soft bodies but stromalites are an exception to this. There are 3 distinct types of genetic changes that can occur to indicate evolution in a cell these are: Nucleotide changes, sequence changes and Horizontal Gene Transfer.
An example of adaptation can be seen with the different E.coli strains, K-12 and O157:H7, K-12 are relatively safe and used in most laboratories however O157:H7 is pathogenic and is responsible for food poisoning, they are not different species but they occur with different adaptations and this can be seen with regard to genome size and using an evolutionary chronometer. Evolution in bacteria can occur for many different reasons, the most common is due to use of antibiotics and environmental stress that can force the organism to change to its environment. Time plays a great role in evolution of the organism also. The micro-organisms have many different methods in order to adapt to the environment and some of these methods are quite advanced.
Method of measuring evolution
Evolution is measured by noticing how similar the strains are or how similar the species are. The most useful method for determining evolution is by using genetic material and creating a comparison. An evolutionary chronometer is generally used to determine the separation of two different genetic sequences, the evolutionary chronometer can be an amino acid or a nucleotide. An evolutionary chronometer has to have the following characteristics:
Universally distributed.
Functionally homologous.
Sequence should be changed with relation to evolutionary distance measured.
Its function must be conserved.
The sequence that is chosen for study depends on the evolutionary distance of the organisms being studied, if the organisms are of the same species then a fast-evolving gene would be chosen to show evolution however if it is two different species then a slow-evolving gene would be used so that there is a comparison between