Collagen-eating microbes may explain why soft-bodied fossils vanished
Rise of collagen-eating microbes may help explain gaps in the fossil record
University of Cambridge researchers traced collagenase genes across 700 bacterial genomes and found the enzymes predate animals, initially confined to oxygen-intolerant microbes. That let Ediacaran soft tissues linger long enough to fossilise. When collagenases spread into oxygen-using bacteria around the Ediacaran–Cambrian transition, decay caught up, and detailed soft-body fossils became rare.
Around this critical time when these soft-bodied animals stopped fossilising, we start seeing the appearance of collagenases in aerobic bacteria, meaning the ability to break down collagen-bearing tissues could start to spread into new environments as animal diversity accelerated.
- pfdietz
Collagen is a foundational class of proteins, found in all animals in large amounts. It's weird -- it has an unusual amino acid, hydroxyproline, that is not directly specified in the standard genetic code (instead, it is made by modification of proline after the protein has been synthesized; this conversion requires vitamin C and its failure is one of the pathologies of scurvy).
One version of collagen, Collagen IV, has this weird sulfur-nitrogen double bound that is produced (again, by post-translational modification) using bromine as a reagent, and for this reason bromine (as bromide) in tiny amounts is a necessary trace element in diets. This last fact was only discovered in 2014.
- qnleigh
It's hypothesized that a similar story played out for lignin, leading to the majority of the world's coal deposits. In the Carboniferous period ~300 million years ago, plants evolved a class of organic polymers called lignins which were difficult to break down. This lead to a massive accumulation of dead plant matter that nothing could digest. It only ended when fungi evolved the ability to break down lignin.
See the section on coal formation here https://en.wikipedia.org/wiki/Carboniferous
- 2b3a51
The speculation about future evolution of bacteria that can digest plastic by using similar enzymes was thought provoking. The actual paper is open access as well and the 'extended pdf' has introductory material that I found interesting.