MICR-4010 Lecture Notes - Lecture 3: Species Problem, Ribosomal Rna, Archaea
9 Sep 2018
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Document Summary
Biological species concept: a species is the "basic unit of ecology" Evolutionary species concept: a lineage evolving separately from others and with its own unitary evolutionary role and tendencies. Microbiology does not have an accepted species concept. Need definition for predictive understanding of species and its environment. Phylogenetic species concept for bacteria and archaea: genetically and phenotypically cohesive. Should share a recent common ancestor excluded by other species. No firm estimate on number of prokaryotic species. ~ all plant and animal species = microbiomes with countless unique microbes. Bacterial and archaeal species = share high degree of similarity. Share recent common ancestry of their small subunit rrna genes. 70% or less dna-dna hybridization and difference in small subunit rrna indicates difference. 70% dna-dna hybridization for classifications that were already in place. 16s rrna gene dones not always provide proper info. Can have more than 90% similarity and still be different species.
