BIOS E-127 – 08.10.20

Microbial species, biogeography & population genetics

Species

“Species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups” (Mayr, 1942)

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)

Ecological species definition?

(Cohan, 2001)

Case of ecotypes: Vibrio

(Thompson et al., 2005)

How follow diversification?

MLST for Streptococcus pneumoniae

(Fraser et al., 2007)

(Feil, 2003)

Population genetic structure from MLST

modest HGT

high HGT

(Feil, 2004)

“Everything is everywhere – the environment selects.” (Baas-Becking, 1934)

Microbial biogeography

Non-random distributions of free-living taxa

(Hughes Martiny et al., 2006)

Why do organisms live where they do?

Single rule may not always apply

(Nesbø et al., 2006)

Slow speciation?

Monday (10/27): **Turn in phylogenetics project

Dynamics of adaptation