MICRB265 Lecture Notes - Lecture 6: Microbial Mat, Prokaryotic Small Ribosomal Subunit, Stromatolite
4 Nov 2017
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Document Summary
Species are fundamental units of diversity and yet what defines a microbial species is controversial. the phylogenetic species concept for bacteria and archaea is the working definition. all species should be: rrna comparison. Monophyletic: should share a recent common ancestor excluded by other species, nowadays based on 16s. Species justifications are based on the judgement of taxonomists. Two taxonomic tools that are used to define which strains belong together as one species are the ssu rrna sequence similarities of two organisms and the indicator of distinct species is 70% or less dna-dna hybridization. 70% hybridization or more = same species. Pairs of microbes are compared based on their 16s rrna similarities and dna-dna hybridization. points in the marked area are likely microbe pairs of the same species. Formal validation of a new genus or species has to follow rules outlined by bacteriological code. 1. detailed description of characteristics/traits and proposed name has to be published.
