Scientists use classification systems to differentiate and identify species in medical microbiology. Bacterial species is a distinct organism that share an overall similar pattern of traits and also share about 95% gene sequence. Individuals members of a given species can also show variations. Microbiologists accordingly use terms like subspecies, strain or type to distinguish the same species that have different characteristics.
Serotype refers to representatives of a species that stimulate a distinct pattern of antibody respones in their hosts becasue of distinct surface molecules. An example is the bacterium E. coli O157:H7 which is a dangerous contaminant of food that can not only cause diarrhea but also necessitate amputations of limbs. Most speies of E. coli are harmless but this train has extra genes that make it pathogenic.
A database caleld Bergey’s Manual of Determinative Bacteriology is based entirely on phenotype characteristics (not genetics) such as shape (seen by microscopy) and metabolic capabilities, such as what is reuqired to grow.
The method of assigning a scientifc or specific anme is called the inomial (two-name) system. The scientific anme is always a combination of the genus name followed by the species name. The genus part is capitalized and the species part begins with a lowercase letter. (e.g., Escherichia coli).
Archaea:
Archaea share many bacterial characteristics but are actually more closely related to Eurkrya due to sharing a number of ribosomal RNA sequences that are not found in bacteria and the similarity of protein syntehsis and ribosomal subunit structures.
Archaea have unique rNA sequences, exhibit different DNA compaction and contain unique membrane lipids, cell wall components and pilin proteins.
Arachea are the most primitive of all life forms and date back to the frist cells that originated on earth 3.8 billion years ago. Earth is thought to have contained a hot, anaerobic soup with sulfuric gases and salts. The modern archaea are called extremophiles and still live in habitats which have some of these conditions. some arhaea thrive in very high temperatures, others like high concentrations of salt or acid to survive. Some live on sulfure, reducing it to hydrogen sulfide to get their energy.