Microbial degradation of biological material is a process essential for life on Earth.
Earth. Some genetic studies have
They break down plant matter, but surprisingly little is known about the decomposition of vertebrates such as humans.
That was until a recent study by scientists at Colorado State University (CSU) identified a network of microbes that appears to “universally” promote the breakdown of animal flesh, regardless of environmental variables.
A research team led by Dr. Jessica Metcalf, associate professor in the Department of Animal Sciences, tracked the decay of 36 human corpses at three body donor sites: the University of Tennessee, Sam Houston State University, and Colorado Mesa University.
Over the course of several years, the bodies were kept in cages and exposed to the natural environment.
After 21 days of exposure, Metcalf and colleagues
Skin and soil samples were taken from each carcass.
A wide range of molecular and genomic studies, including gene sequences and metabolites
Analyze.
Amazingly, the same 20 species of microorganisms were identified in all 36 bodies.
the type of climate and soil they have been exposed to.
The network includes signatures such as Obritimonas alkaliphila, Ignatucineria, Wolfhartimonas, Bacteroides, and Bagococcus luthrae, representing a “unique phylogenetic diversity” that is rare or undetected in host-associated or soil microbial communities in the American Gut Project and Global Microbiome Project datasets. These two large-scale studies characterize human microbial communities. However, because the microbes are found in insects, they suggest that insects act as “vectors” to carry the microbes to humans.
To decompose the corpse.
“We see similar microbes appearing at similar times during decomposition.
Regardless of all the variables that can be considered outdoors,” Metcalf said.
Understanding the composition and timing of the microbes that break down human flesh has important implications for the field of forensic science, and Metcalfe and his colleagues applied a machine learning approach to the data to build a tool that can predict with high accuracy how long it has been since a body decomposed.
This period, also known as the postmortem period,
Decipher when the remains were exposed to harsh environmental conditions.
Technology Network spoke with the CSU research team to learn more about how the study, which is based on more than a decade of research, was conducted and how the data was used to
It helps regulate the decomposition process in the human death industry.
Q: Can you explain why, prior to this work, so little was known about the decomposition ecology of vertebrates?
A: Microorganisms are known to play a key role in the decomposition of vertebrate carcasses, including humans. However, the intricacies of how members of the decomposing microbial community react and interact with each other, and in particular how these activities compare with climate, are poorly understood.
The reason for this lack of knowledge is
The decomposition field has focused on the breakdown of plant material.
The biomass on Earth is much greater.
Q: Why did you choose a 21-day observation period?
A: The 21-day period was chosen because it is the period of most active decomposition in vertebrates, when the most significant changes occur to the body, the environment, and the cells.
Microbial communities. By choosing this time frame,
Microorganisms are responding to these dynamic changes.
Q: This study generated a large amount of molecular and genomic information from the samples. Can you summarize the different methods you used to analyze this data and why?
A: We sequenced a gene that is essential in all prokaryotes, called the 16S rRNA gene. By sequencing this gene, we can identify the microbial members in the system and measure their relative abundance at each time point.
The eukaryotic gene 18S rRNA plays a similar role in eukaryotes.
Microscopic eukaryotes in the system.
In addition, we performed metagenomic sequencing to study bacterial functional genes, such as their ability to produce or use specific nutrients. We were also able to assemble several key bacterial genomes using metagenomic data, providing our field with the first microbial decomposer database. Finally, we generated metabolomic data, which are profiles of several nutrients and resource types in the environment.
Q: Can you tell us a bit more about generalist decomposers? What are some of the key microbes in that community? Were there any that surprised you?
A: These universal decomposers are organisms that have been found to be associated with active and advanced decomposition stages in all climates. These include
The organisms include bacteria known to be associated with blowflies.
There are ruins such as Ignatcinaria, which are nothing spectacular, but there are also some lesser known sites such as Obritmonas.
Q: You’ve found universal decomposers in insects, meaning that they “import them” to corpses. Can you tell us a bit more about these insects? Are they found all over the world, and are they under environmental pressure?
A: Yes, insects act as vectors to and from corpses.
They take in microorganisms and expel them through ingestion and excretion.
They also lay eggs which hatch into maggots and lay or pick themselves up.
microbes. And when the flies and maggots leave, they take some of these microbes with them.
These insects include flies,
Beetles and ants.
There have been studies where decomposition has been controlled to exclude insects, and while some of the same microbes we detected are certainly present, the insect-specific microbes are not. The decomposition process still occurs, but it proceeds more slowly in the absence of insects, and tissue may even remain in the corpse for longer.
“I feel like we’re opening up a lot of avenues in basic ecology and nutrient cycling,” Metcalf said.
Q: The experimental setup (keeping human bodies in cages all over the research facility, exposed to the elements) may be interpreted as extremely cruel by some. We understand that this is the only way to collect data that reflects a real-life scenario of human decay, but could you, as a research team, describe how you felt during this study experience?
A: The ultimate goal of studying human corruption is
Improve society. This can be done by finding ways to be more environmentally friendly.
deaths and improve our understanding of important ecological processes;
We will mediate between them and conduct forensic investigations to ensure justice is served.
As researchers, it is important to keep these benefits in mind when conducting research, and it is also crucial to treat donors and their samples with the utmost respect, as they willingly donate for the betterment of society.
Q: Can you talk about the process of donating a body for research?
A: The three facilities we collaborated with in this research are what we consider to be “willing bodies.”
The option to donate their bodies to a specific facility was so important to the donors in this study that they volunteered to donate their bodies to a specific facility while they were alive. This request was approved by the facility, and the donor’s next of kin, lawyer, or physician ensured that the donor’s wishes were communicated and fulfilled.
Q: In the paper’s discussion, you say the data could help regulate the decomposition process in the human death industry. What does this mean?
A: The human death industry is subject to space availability, etc.
Burial cemeteries and the generation of volatile substances and greenhouse gases
From cremation, which allows for more environmentally friendly disposal
There have been many studies done on the dead. For example, human composting
Reburying human remains in nutrient-rich soil in a completely natural way
They are used to help plants grow and restore damaged habitats.
Through the study of the microorganisms involved in decomposition, we aim to improve our understanding of these processes and increase their efficiency.
Dr Jessica Metcalfe and Dr Zachary Burcham spoke to Molly Campbell, senior science writer at Technology Network.
