Stromatolites—and their close relatives, microbial mats—could be mistaken for what seems like a bunch of old dark rocks. But instead, they are dense, layered communities of microbes. Long before complex life such as animals or plants existed, stromatolites breathed the first molecules of oxygen into Earth’s atmosphere. Now, in a study published in Current Biology, researchers say they may also hold insights into how complex life began.

Associate Professor Brendan Burns, an evolutionary microbiologist at UNSW Sydney, is part of a team that identified a previously unknown microbe living in close partnership with another organism inside these “living fossils.” The work, co-led with researchers from the University of Technology Sydney and The University of Melbourne, could help solve one of life’s biggest mysteries: how simple cells first combined to form more complex life.

“Stromatolites could be more than ‘just’ a cradle of life where early microbial life flourished,” says A/Prof. Burns.

Here’s a very nice review on the molecular biology of endocytosis and endosomal trafficking. Found it very helpful for better understanding these pathways.

This brief overview of endocytic trafficking is written in honor of Renate Fuchs, who retires this year. In the mid-1980s, Renate pioneered studies on the ion-conducting properties of the recently discovered early and late endosomes and the mechanisms governing endosomal acidification. As described in this review, after uptake through one of many mechanistically distinct endocytic pathways, internalized proteins merge into a common early/sorting endosome. From there they again diverge along distinct sorting pathways, back to the cell surface, on to the trans-Golgi network or across polarized cells. Other transmembrane receptors are packaged into intraluminal vesicles of late endosomes/multivesicular bodies that eventually fuse with and deliver their content to lysosomes for degradation. Endosomal acidification, in part, determines sorting along this pathway.