Permanent URL to this publication:
http://dx.doi.org/10.5167/uzh-46196 Background: Cyanobacteria
are one of the oldest and morphologically most diverse
prokaryotic phyla on our planet. The early development of an
oxygen-containing atmosphere approximately 2.45 - 2.22 billion
years ago is attributed to the photosynthetic activity of
cyanobacteria. Furthermore, they are one of the few prokaryotic
phyla where multicellularity has evolved. Understanding when and
how multicellularity evolved in these ancient organisms would
provide fundamental information on the early history of life and
further our knowledge of complex life forms. Results: We
conducted and compared phylogenetic analyses of 16S rDNA
sequences from a large sample of taxa representing the
morphological and genetic diversity of cyanobacteria. We
reconstructed ancestral character states on 10,000 phylogenetic
trees. The results suggest that the majority of extant
cyanobacteria descend from multicellular ancestors. Reversals to
unicellularity occurred