Species
“Species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups” (Mayr, 1942)
OEB 192 – 10.09.27
Microbial species
“…a category that circumscribes a (preferably) genomically coherent group of individual isolates/strains sharing a high degree of similarity in (many) independent features, comparatively tested under highly standardized conditions” (Stackebrandt et al., 2002)
“…characterized by a certain degree of phenotypic consistency, showing 70% of DNA-DNA binding and over 97% of 16S ribosomal RNA (rRNA) gene-sequence identity” (Vandamme et al., 1996)
Microbial species
(Konstantinidis & Tiedje, 2005)
Evidence of species?: clusters of microheterogeneity
(Acinas et al., 2004)
Genome vs. 16S rRNA diversity?
(Thompson et al., 2005)
How do new species emerge?
Allopatric speciation
Sympatric speciation
“Everything is everywhere – the environment selects.” (Baas-Becking, 1934)
Microbial biogeography
Ubiquitous dispersal?
• Diversity of Paraphysomonas
(Finlay, 2002)(Finlay & Clarke, 1999)
Non-random distributions of free-living taxa
(Hughes Martiny et al., 2006)
Biogeography: Sulfolobus
(Whitaker et al., 2003)
Microbes in a host w/ biogeography: Helicobacter pylori
(Falush et al.,2003)
Ecological species definition?
(Cohan, 2001)
Case of ecotypes: Prochloroccus
(Johnson et al., 2006)
Single rule may not always apply
(Nesbø et al., 2006)
Wednesday (9/29): Microbial speciation
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