Did the origin of muticellularity in cyanobacteria trigger the Great Oxidation Event?
| Dates: | 23 February 2015 |
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| Times: | 12:00 - 13:00 |
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| What is it: | Seminar |
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| Organiser: | Faculty of Life Sciences |
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| Who is it for: | University staff |
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| Speaker: | Dr Bettina E Schirrmeister |
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Computational and Evolutionary Biology Seminar Series 2015
At the end of the Archean cyanobacteria rapidly oxygenated Earth's atmosphere,
during the so called Great Oxidation Event (GOE) and redefined evolutionary space,
allowing for aerobic life to evolve. Competing hypotheses have argued (i) that the
GOE was caused by the origin of cyanobacteria, or (ii) that oxygen accumulated
already 3.0 Ga due to cyanobacteria, but was originally lost in oxygen sinks, such as
reduced volcanic gases, which delayed the GOE to 2.45 Ga. Yet, none of those
hypothesis take into account how evolutionary innovations among cyanobacteria
could be associated to their success and consequently oxygen production.
Additionally, it is difficult to infer cyanobacterial history, due to (i) the scarceness of
Precambrian deposits, (ii) limited characteristics for identification of taxa and (iii) the
poor preservation of ancient microfossils. Combining molecular analyses, such as
phylogenomics and divergence time estimations with fossil data may provide novel
inferences regarding early cyanobacterial diversity and help to understand how they
influenced the early history life and Earth.
Based on 16S rRNA I have suggested that the origin of multicellularity within
cyanobacteria might have been associated with the GOE. However, single gene
analyses have their limitations, especially for deep branches. Recently, I have
reconstructed the evolutionary history of cyanobacterial using (i) genomic data and
(ii) re-evaluated the Precambrian fossil record to get more precise calibrations for a
relaxed clock analysis. Phylogenomic Maximum Likelihood trees based on 756 gene
sequences of 65 cyanobacterial taxa support previous findings of an ancient
multicellular cyanobacterial lineage being ancestral to the majority of modern
cyanobacteria including most unicellular taxa. The origin of multicellularity could
have provided an advantage during the colonisation of new habitats. Multicellular
cyanobacteria are known to position themselves within bacterial mats so that they
maximize metabolic and photosynthetic rates. In an ozone free Archean environment
this could have been a major advantage to avoid lethal UV-C levels.
Speaker
Dr Bettina E Schirrmeister
Organisation: University of Bristol
Travel and Contact Information
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Michael Smith Lecture Theatre
Michael Smith Building
Manchester
