Saw this tweet a few minutes ago:

Human-Infection-Derived Bacteria Provide Insights intoEvolutionary Origins of Mutualistic Insect–Bacterial Symbioses bit.ly/U5Uwx5
— Peter van Baarlen (@pvanbaarlen) November 30, 2012

The title of the paper took me a reread or two to understand.  But once I got what they were trying to say I was intrigued.  And so I went to the paper:  PLOS Genetics: A Novel Human-Infection-Derived Bacterium Provides Insights into the Evolutionary Origins of Mutualistic Insect–Bacterial Symbioses.  And it is loaded with interesting tidbits.  First, the first section of the results details the history of the infection in a 71 year old male and his recovery and the isolation and characterization of a new bacterial strain.  Phylogenetic analysis revealed this was a close relative of the Sodalis endosymbionts of insects.


And then comparative genomics revealed a bit more detail about the history of this strain, it's relatives, and some of the insect endosymbionts.  And plus, it allowed the authors to make some jazzy figures such as


And this and other comparative analyses revealed some interesting findings.  As summarize by the authors

Our results indicate that ancestral relatives of strain HS have served as progenitors for the independent descent of Sodalis-allied endosymbionts found in several insect hosts. Comparative analyses indicate that the gene inventories of the insect endosymbionts were independently derived from a common ancestral template through a combination of irreversible degenerative changes. Our results provide compelling support for the notion that mutualists evolve from pathogenic progenitors. They also elucidate the role of degenerative evolutionary processes in shaping the gene inventories of symbiotic bacteria at a very early stage in these mutualistic associations.

The paper is definitely worth a look.