Prescott's Microbiology 8th Edition by Joanne Willey, Linda Sherwood, Christopher J. Woolverton, Lansing Prescott, John Harley, Donald Klein

Exercise 5

Scientists are very interested in understanding when cyanobacteria first emerged because, as the first organisms capable of oxygenic photosynthesis, they triggered a sharp rise in atmospheric oxygen. For many years, the oldest fossil evidence for cyanobacteria was dated at 2.15 billion years ago (bya). In the late twentieth century, lipid biomarkers werereported from geological samples from Western Australia that indicated that cyanobacteria were present 2.7 bya. In 2008, however, it was determined that these lipids were contaminants and the accepted value for the rise of cyanobacteria reverted to 2.15 bya. Discuss the specific challenges encountered in the study of microbial evolution. Contrast these with the advent of the use of molecular markers such assmall subunit rRNA nucleotide sequences to assess microbial evolution.

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Studying the evolution of microbes presents many challenges, such as degraded specimens, contaminants, and having to tease out lineages for an organism that replicates quickly and is capable of horizontal gene transfer.