Larry writes:

Doctors Elde and Racaniello,

(I’m the software developer fanboy who wrote in many months ago. Still a big fan.)

I just listened to TWIM-190 (December(!)) with the two papers on exosomes — a great show, as usual.

I was intrigued by the fact that exosomes are secreted (universally?) by archaea, bacteria and eukaryotes.

My first question: since there’s (I would assume) a big energy cost to producing and releasing these vesicles with protein and/or mRNA/miRNA or even double-stranded DNA … what’s the benefit to the cells for doing so?

The wiki page indicates inter-cellular communication triggering other cells to do something useful to the originating cell, so, I would guess the answer, generally speaking, is parasitism and mutualism.

And, IIUC, horizontal gene transfer seems implied, so… question #2: is this how genes become selfish?

In any case, this mix of complex yet universal behavior leads this very na├»ve listener to question #3 – brace for wild, uninformed speculation – whether exosomes are (or echo) the original form of (one level of) basic building blocks of life that at some point (or two points) embedded themselves in lipid bags to become archaea & bacteria cells, thus making a great leap forward in stability, akin to the eukaryotic energy leap?

Apologies for all the parenthetical remarks,

Larry West

San Diego – where it’s getting near freezing at night in the inland valleys this week.

(Now I’m going to have to re-read Nick Lane to see whether he actually mentions this and I just didn’t understand it.)

PS On further thought, those questions seem too naive for your show, but if you could briefly discuss current thinking on pre-cellular evolution, the “RNA world”, and connections, if any, with exosomes, that would be very interesting.

Belated thanks,


Anthony writes:

Archaic admixture in the human genome

A Genetic Atlas of Human Admixture History