Saw this tweet a few minutes ago:
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.
Well I was torn about this. Should I title the post ” ICE, ICE, Bacterial BABIES” or say something about sex? I settled on sex, but not sure if that was wise.
Anyway – quick post to say that there are two papers from PLoS Genetics last month that caught my eye. They are
The latter is a “review” paper linked to the first one which is a research paper. The papers together provide both a good background and a window into modern studies of “ICEs” or integrative conjugative elements in bacteria.
I like the summary from the first paper:
Some mobile genetic elements spread genetic information horizontally between prokaryotes by conjugation, a mechanism by which DNA is transferred directly from one cell to the other. Among the processes allowing genetic transfer between cells, conjugation is the one allowing the simultaneous transfer of larger amounts of DNA and between the least related cells. As such, conjugative systems are key players in horizontal transfer, including the transfer of antibiotic resistance to and between many human pathogens. Conjugative systems are encoded both in plasmids and in chromosomes. The latter are called Integrative Conjugative Elements (ICE); and their number, identity, and mechanism of conjugation were poorly known. We have developed an approach to identify and characterize these elements and found more ICEs than conjugative plasmids in genomes. While both ICEs and plasmids use similar conjugative systems, there are remarkable preferences for some systems in some elements. Our evolutionary analysis shows that plasmid conjugative systems have often given rise to ICEs and vice versa. Therefore, ICEs and conjugative plasmids should be regarded as one and the same, the differences in their means of existence in cells probably the result of different requirements for stabilization and/or transmissibility of the genetic information they contain.
That should be enough to get people started. And that is alas all I have time to write about here.
There is an interesting interview of David Botstein in PLoS Genetics here.
Botstein has been at the heart of many key discoveries and innovations in genetics and genomics and he discusses some of these in this interview. In addition he discusses his initiative at Princeton to try a new way of teaching science to undergraduates. It is not the most comprehensive interview, but it still has some juicy tidbits. In particular, the discussion of his 1980 paper on genetic mapping has some things I have not read elsewhere.