Lateral Gene Transfer from Bacteria to Animals - Evidence for Pansexuality?

Ok, so maybe we will never know whether our human ancestors got it on with Neanderthals, but new evidence seems to indicate that bacteria can have sex with flies and worms. Well, sort of. A new paper in Science shows that pretty massive chunks of the Wolbachia bacterial genome can be found in the genomes of a variety of multicellular eukaryote species, including flies and worms. Wolbachia are endosymbionts that can be found in germ cells, so presumably this has facilitated accidental incorporation of microbial DNA into the animal germline.

Even more interesting is the implication that bacterial LGT may be occurring in many other species of higher eukaryotes, including humans. Current practice in the world of genomic sequencing is to filter out bacterial sequence on the assumption that it must be an environmental contaminant; these findings suggest that some bacterial sequence that has been excluded from existing genome assemblies may actually belong there.

Mitochondrial Madness

Our often-neglected bacterial endosymbionts the mitochondria seem to have their fingers in all aspects of eukaryotic cell functioning. Not only do they make us ATP and tell our cells when to die, they even have their own genome, which they can replicate, transcribe and translate all on their own. But mitochondria don't just use proteins encoded in their own genomes; they've also got some out on loan from the nucleus. And this is where the madness begins. Somehow this excellent Molecular Cell review on mitochondrial transcription found its way onto my lab bench, so I read it. Here are a few of the mind-blowing facts you can discover therein:

• The eukaryotic single-subunit mitochondrial RNA polymerase was ganked from bacterial viruses (bacteriophage T3/T7), and has no relation to those encoded by bacteria themselves.

• Even weirder, the phage-like mtRNA polymerase is encoded in the nuclear genome of eukaryotes. Interstingly, an isoform of mtRNA polymerase lacking a mitochondrial localization signal performs transcription of nuclear-encoded genes in the nucleus (RNA pol IV).

• The amino-terminal domain of yeast mtRNA polymerase has diverged from its phage ancestry, and has evolved to mediate coupling between mitochondrial transcription and translation. In fact, mutations in the ATD lead to deficiencies in mitochondrially-encoded OXPHOS enzymes and thereby decrease lifespan in yeast.

• What? Mitochondrial translation? What's up with that? Nobody really knows...

Also, check out this wicked album of artistic renditions of cells by Gary Carlson which I ganked the above photo from. Nice job Gary!