Buried human bodies provide a buffet of nutrients to microbes, which digest the remains, eventually tunneling into the skeleton. They secrete enzymes, turning solid bones into a porous, crumbling scaffold.
For their study, Kaptan, Hollund relied on human remains excavated from medieval Norwegian graves.
The Museum of Archaeology, University of Stavanger, CC-BY 4.0
Researchers reported degradation of bones by microorganisms for the first time in the 1800s.1 Since then, microscopy and chemical analyses have offered insights into how microbial action changes bone structure and chemistry.2,3 Despite these advances, scientists had not combined microscopy analyses with bone microbiome studies, preventing a better understanding of which microbes drive bone degradation.
To bridge this gap, researchers led by University of Stavanger conservation scientists Damla Kaptan and Hege Ingjerd Hollund subjected human bone samples to microscopy and metagenomics. They discovered distinct microbiome profiles in bones at different levels of degradation. Their findings, published today in PLoS One, offer novel information into how microbes could contribute to bone preservation and decay.4
“The dead still have stories to tell,” said Kaptan in a statement. “Ancient bones are not biologically silent remains. They contain rich microbial signatures that can reveal how bones change over centuries after burial.”
For their study, Kaptan, Hollund, and their colleagues studied bone samples from 83 bodies buried between the 11th and 19th centuries in Norwegian cemeteries. Histological analyses using microscopy revealed that the remains showed different levels of preservation: Older bones and those buried at outdoor locations were more degraded than newer ones and those buried inside churches.
Tunnelling by bone-eating microbes caused solid bones to turn porous (upper half), while well-preserved parts of the bone retained its intact microanatomy (lower half).
Hege Ingjerd Hollund, CC-BY 4.0
In addition to peeking into the excavated remains, the researchers extracted ancient DNA from the samples and carried out metagenomic sequencing. They found that different microbes were present the bones depending on how well-preserved the samples were. Those with extensive erosion had a higher abundance of bacteria belonging to the genus Streptosporangium and moderately eroded samples contained Lysobacter. Microbes belonging to both these genera have genes that code for enzymes that could potentially break down collagen, contributing to bone degradation. In contrast, Streptomyces dominated the well-preserved samples.
Kaptan, Hollund, and their colleagues also observed that microbiomes from newer, indoor, and more well-preserved bone samples showed the highest diversity. This is likely because well-preserved bones have more nutrients to support microbial life.
In the statement, Hollund said that this is the first time in her 15-year career that she has been able to name microbes that are potentially responsible for degrading bones in human remains. “That is both incredibly exciting as well as gratifying,” she said.
- Wedl CK. About a fungus that germinates in the tooth bud and bone. Sitzungsberichte Akad Wiss Math-Naturwissenschaftliche. 1865;50:171–193.
- Bell LS, et al. Diagenetic alteration to teeth in situ illustrated by backscattered electron imaging. Scanning. 1991;13(2):173-183.
- Child AM. Towards an understanding of the microbial decomposition of archaeological bone in the burial environment. J Archaeol Sci. 1995;22(2):165–174.
- Kaptan D, et al. Histological and metagenomic analysis of microbial communities in archaeological human bones. PLoS One. 2026;21(5):e0340244.
