TL;DR
Prime made for students and young adults
- Fast, free delivery for dorm and study essentials
- Prime Video and Amazon Music included
- Member-only deals
A study in Current Biology traces collagenase genes across 700 bacterial genomes and proposes that their spread into oxygen-using microbes helped reduce the preservation of soft-bodied animals. The timing aligns with a major decline in soft-tissue fossils, but the research offers a possible explanation, not proof that microbial enzymes alone caused the change.
A Cambridge-led study proposes that the spread of collagen-digesting enzymes among bacteria may help explain why soft-bodied animal fossils became less common around the transition from the Ediacaran to the Cambrian Period, about 539 million years ago. The researchers traced collagenase genes across 700 bacterial genomes and compared their history with the fossil record; they describe the connection as a possible explanation, not a demonstrated single cause.
Collagen is a structural protein that gives support to animal tissues, including tissues that are not mineralised. Enzymes called collagenases break it down. The study’s proposed mechanism is that when microbes able to digest collagen became more widespread in oxygenated environments, dead animals could decay before their soft tissues were buried and preserved.
The researchers report that collagenases predate animals and were initially found in anaerobic microbes, which do not use oxygen. They suggest that, in oxygenated Ediacaran waters, collagen in a dead animal might persist until surrounding sediment lost its oxygen, giving the tissues more time to fossilise. Around the Ediacaran-Cambrian boundary, collagenases spread into more microbial groups, including aerobic bacteria associated with modern decay.
The timing of that expansion corresponds with a marked decrease in the abundance of soft-bodied fossils, according to the researchers. The study, titled “Temporal heterogeneity in the animal fossil record driven by proliferation of microbial collagenases,” was published in Current Biology. Its findings link a biological change in decay processes to a change in what is preserved, while leaving room for other conditions to affect individual fossil sites.
How Bacterial Decay Could Reshape Fossils
The fossil record is an incomplete account of past life: bones, shells and teeth are more likely to survive than muscles, organs or skin. If microbes’ ability to consume collagen changed over geological time, then the absence of soft-bodied fossils may reflect not only which animals lived, but also how quickly their tissues decayed after death.
The proposed explanation could help researchers interpret an apparent contrast in the record. Late Ediacaran sites sometimes preserve animals without hard parts in remarkable detail, while later soft-bodied remains are much less common. A change in microbial decay could provide an overarching factor alongside local conditions such as sediment chemistry, burial speed and the environment where an animal died. It does not mean that all later soft tissue was impossible to preserve: the researchers note that rapid burial can still protect remains.
The work also addresses a longstanding puzzle in early animal evolution. The late Ediacaran, from 579 million to 539 million years ago, includes some of the oldest known complex animal forms, many preserved despite lacking mineralised skeletons. Understanding why those animals fossilised can help scientists distinguish changes in ancient ecosystems from changes in the processes that preserve evidence of them.
paleontology fossil identification field guide book
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
From Ediacaran Preservation to Cambrian Decline
Soft tissues are generally less likely to fossilise than hard body parts, so most known fossils are mineralised structures. Yet some late Ediacaran deposits preserve whole communities and fine details of organisms that had no hard parts. Scientists have proposed several explanations, including unusual ocean chemistry, differences in tissue composition and microbial films on the seafloor. The Cambridge team says these factors may explain preservation at particular locations but do not provide an explanation that applies everywhere.
To investigate another possibility, lead author Philip Vixseboxse and colleagues traced the evolutionary history of microbial collagenase genes through 700 bacterial genomes, then compared the results with a time-dated evolutionary tree. Their analysis indicates that the enzymes existed before animals and later appeared in a wider range of microbes. The researchers interpret this expansion as a potential shift in the conditions governing whether collagen-bearing remains survived long enough to fossilise.
The authors also draw a limited analogy with plastic. Vixseboxse said microbes did not have a reason to efficiently degrade collagen before it became an available food source; the study suggests that microbial enzymes could likewise evolve to use abundant polymers. That comparison is speculative and is not a finding that the research predicts when or whether plastic-degrading microbes will become widespread.
“If you think about a modern jellyfish, for example, if it washes up on a beach and is left to decay, it will decompose in a matter of days.”
— Philip Vixseboxse, lead author, who completed the work while a PhD candidate in Cambridge’s Department of Earth Sciences
Ediacaran Cambrian fossils science book
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Limits of the Proposed Decay Link
The study identifies a timing and evolutionary association, but the source material does not establish that the spread of collagenases directly caused the decline in soft-bodied fossils. The fossil record is uneven, and preservation depends on burial, local chemistry, oxygen levels and other conditions. The researchers acknowledge that exceptional preservation continued in younger rocks under favourable circumstances.
It is also unclear how much of the observed change can be attributed to microbial enzymes compared with the other explanations proposed for Ediacaran fossil preservation. The reported genome analysis traces gene histories; it does not by itself show how quickly collagen broke down in every ancient environment. The study therefore supports a possible mechanism while leaving its relative importance and geographic reach unresolved.
beginner compound microscope for biology and microbiology
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Testing the Mechanism Across Fossil Sites
The next step is to assess whether the proposed mechanism fits evidence from a wider range of fossil deposits and ancient environments. Comparisons across sites could help determine whether the timing of collagenase expansion corresponds to changes in preservation after accounting for differences in sediment, oxygen availability and burial conditions.
The report does not announce a follow-up experiment or a scheduled next milestone. For now, the finding is a hypothesis that can guide further research into how microbial evolution influenced the fossil record, rather than a final explanation for the disappearance of soft-bodied fossils.
bacterial evolution and microbial ecology textbook
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Key Questions
What did the researchers propose?
They propose that collagen-digesting microbial enzymes called collagenases became more widespread around the Ediacaran-Cambrian transition, allowing soft tissues to decay faster and reducing their chance of fossilisation.
How did the team study collagenases?
The researchers traced collagenase genes across 700 bacterial genomes and compared their inferred evolutionary history with a time-dated tree of life.
Does the study prove that microbes caused the fossil decline?
No. The study reports a timing relationship and proposes a mechanism. It does not establish that collagenases were the sole or direct cause of fewer soft-bodied fossils.
Why were some Ediacaran animals preserved so well?
The study suggests that collagen may have persisted in oxygenated settings until oxygen in surrounding sediment was depleted, allowing more time for burial and fossilisation. Local conditions also matter, and the reason for exceptional preservation is not settled.
Can soft tissues still fossilise after the Ediacaran?
Yes. The researchers say soft tissues can be preserved in younger rocks in exceptional circumstances, such as when an animal is buried rapidly after death. Such preservation is rare.
Source: hn
Halloween Picks
halloween
As an affiliate, we earn on qualifying purchases.
