Spontaneous mutations of a model heterotrophic marine bacterium.

摘要: Heterotrophic marine bacterioplankton populations display substantive genomic diversity that is commonly explained to be the result of selective forces imposed by resource limitation or interactions with phage and predators. Here we use a mutation-accumulation experiment followed whole-genome sequencing mutation lines determine an unbiased rate molecular spectrum spontaneous mutations for model heterotrophic bacterium in globally important Roseobacter clade, Ruegeria pomeroyi DSS-3. We find evidence mutational bias towards deletions over insertions, this process alone could account sizable portion genome size among roseobacters also implies lateral gene transfer and/or selection must play role maintaining large sizes. favor changes from A/T G/C nucleobases, which explains widespread occurrences G/C-enriched genomes. Using calculated 1.39 × 10-10 per base generation, implement 'mutation-rate clock' approach date evolution assuming constant along their evolutionary history. This gives estimated expansion good agreement earlier fossil-based estimate ~250 million years ago consistent hypothesis correlated history between eukaryotic phytoplankton groups.