Well-preserved archaeological bone samples have different microbial communities than heavily degraded bone samples, providing a new understanding of how microbes contribute to bone degradation, according to a study published May 27, 2026 in the open-access journal PLOS One by Damla Kaptan from the University of Stavanger, Norway, and colleagues. This study combines detailed analyses of archaeological bone degradation with analyses of microbiome diversity, providing new insights into how microbes may contribute to long-term bone preservation and decay.
Since the 1800s, researchers have known that microbes contribute to bone degradation in archaeological samples. But even today, we still don't know much about how microbial bone degradation occurs or what microbes are responsible.
For this study, researchers analyzed bone samples from medieval cemeteries in southwestern Norway, dating back between the 11th and 19th centuries. Some of the bones had originally been buried outdoors, and some were originally deposited in indoor locations, such as below a church nave. Bone degradation tended to be more extensive in samples from outdoor locations, and in older bones.
The researchers found that differently degraded bones hosted distinct microbial communities, with Lysobacter and Streptomyces among the genera associated with moderately degraded and well-preserved bones, respectively. Some Streptomyces and Streptosporangium bacteria are known to produce enzymes that break down collagen, which could be a factor in bone degradation.
The researchers also noted that microbial diversity tended to be higher in newer bones, bones from indoor locations, and well-preserved bones. This could be because more well-preserved bones have more nutrients and structures that can host microbial life — and could indicate that bones may be able to stay relatively intact even while hosting certain microbes.
Because DNA can break down over time, this study wasn't able to distinguish many specific species from the samples. The team also noted that their samples might be accidentally contaminated with remnants of DNA deposited during excavation, handling, and storage. Nonetheless, this study is a groundbreaking step forward in our understanding of microbial bone degradation — a ubiquitous phenomenon in archaeological samples.
Damla Kaptan adds: "Ancient bones are not biologically silent remains. They contain rich microbial signatures that can reveal how bones change over centuries after burial."
"The dead still have stories to tell. Some bodies disappear rapidly after burial, while others remain preserved for centuries. Even today, we do not fully understand why. Our research explores the hidden microbial processes that may shape decay and long-term preservation in human bones."
Hege Ingjerd Hollund adds: "For more than fifteen years I've been observing and documenting the bioerosion of archaeological skeletons in the microscope, i.e. the tunnels and traces that presumed bacteria make in buried bone. By combining microscopy with analyses of old DNA found in the same bone sample, I've been able to give a name to potential perpetrators for the first time. That is both incredibly exciting as well as gratifying. I think we are onto something when we find bacteria of the genus Streptomyces in almost all our samples."
In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/4tIufwh
Citation: Kaptan D, Flemming Elvers AC, Kjær Knudsen A, Schroeder H, Hollund HI (2026) Histological and metagenomic analysis of microbial communities in archaeological human bones. PLoS One 21(5): e0340244. https://doi.org/10.1371/journal.pone.0340244
Author countries: Norway, Denmark.
Funding: This work is part of an ongoing research project funded by the Research Council of Norway (project number 301877).
