Archaeological bone samples can contain vital clues to what the past was like and how life evolved. Among those clues are also tiny microbial communities that may, according to new research, impact the preservation of these bone samples.
Science has long known that microbes contribute to bone decay through a process known as bioerosion — the breakdown of bone by microorganisms. Yet little is known about how this decay occurs and which of these tiny organisms is responsible. But that may now change.
Publishing their findings in PLOS One, researchers from the University of Stavanger, Norway, reveal that well-preserved bone samples harbor distinct microbial communities compared with heavily degraded samples. This study offers new insights into the role microbes may play in bone preservation or decay.
“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,” Damla Kaptan, the lead study author, said in a press release.
Analyzing Norway’s Ancient Bones
A section of human femur under a microscope displaying signs of bioerosion.
(Image Credit: Hege Ingjerd Hollund, CC-BY 4.0)
For the study, the team analyzed bone samples from 83 individuals, all collected from six cemeteries in southwestern Norway. The remains dated to between the 11th and 19th centuries, and, from what the team could confirm, many came from soil burials, where the body was laid to rest in wooden coffins, though a few came from a brick burial chamber.
The samples included bones from indoor burial sites, such as those within a church, while others had been buried outside. The team noted that bones from outside locations showed greater signs of degradation than those buried inside. The study also revealed that microbial diversity increased around new bones, well-preserved bones, and bones from indoor burial locations.
“Ancient bones are not biologically silent remains. They contain rich microbial signatures that can reveal how bones change over centuries after burial,” Kaptan said.
Read More: New Method Could Unlock Diet, Disease, and Daily Life of Ancient Human Remains
Identifying the Microbes Around the Bones
For their analysis, the team used light microscopy and DNA extraction (among other methods) and observed that the bones had distinct microbial communities based on their degradation. They also identified several microbial genera, including Lysobacter — mostly associated with moderate bone degradation — and Streptomyces — mostly associated with well-preserved bones.
Unfortunately, because DNA tends to break down over time, the team found it difficult to distinguish more specific microbe species from the bone samples. Further still, the team worries that their samples may have been contaminated with DNA from past researchers during excavation and storage.
“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,” co-author Hege Ingjerd Hollund said in the press release.
“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,” Ingjerd Hollund concluded.
Read More: Medieval Skeleton Reveals What Life Was Like With a Disability in the Middle Ages
Article Sources
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- This article references information from a study published in PLOS One: Histological and metagenomic analysis of microbial communities in archaeological human bones
