Nav: Home

Vertebrate decomposition study provides potential new tool for forensic science

December 10, 2015

A new study led by the University of Colorado Boulder and the University of California, San Diego indicates unique and changing microbial communities present during the decomposition of human cadavers look to be a reliable "clock" for forensic scientists.

The study showed some microbial communities associated with humans tick in a predictable, clock-like succession following death, said CU-Boulder and UC San Diego Senior Research Associate Jessica Metcalf, who led the study with UC San Diego Professor Rob Knight. The study also showed the method could not only be used to estimate time of death in different seasons, but as a way to determine the original location of moved corpses and even help in locating buried corpses.

"We feel there is great promise that our findings could be used by forensic scientists," said Metcalf of CU-Boulder's Department of Ecology and Evolutionary Biology. "We view it as potential method that could be used with other lines of evidence by investigators attempting to solve suspicious crimes."

A paper on the subject is being published in the Dec. 10 online issue of Science.

The study involved 25 researchers from 11 institutions and Sam Houston State University's Southeast Texas Applied Forensic Science Facility (STAFSF), a seven-acre outdoor human decomposition research lab. Located in Huntsville, Texas, the facility contains cadavers previously willed to STAFSF. These donations allow students, law enforcement officials, scientists and medical experts to study bodies in various decomposition stages, aiding them in forensic science situations.

In addition to studying human cadavers, the team studied the decomposition of mice on three different soil types: desert, short-grass prairie and high alpine forest. Surprisingly, the "decomposer" microbial communities under mice were similar in all three soils, much like the predictable succession in soils beneath the human cadavers. Metcalf said "decomposer" microbes are ubiquitous but rare in and on our bodies as well as in the environment before death occurs, but become abundant after death.

Each human harbors up to an estimated 100 trillion microbes - as many as 10 times the number of cells in the body - that undertake functions ranging from food digestion to strengthening of the immune system, said Knight, a professor in both the Department of Pediatrics and the Department of Computer Science and Engineering at UC San Diego. The team used powerful gene-sequencing techniques to chart microbes present on cadavers and associated soils in both time and location immediately following death.

"Advances in genetic sequencing technologies now allow us to find patterns in large, diverse populations of microorganisms, see how they associate with specific individuals, and understand how they change over time in a way we couldn't just a few years ago," said Knight, who leads the UC San Diego Microbiome and Microbial Sciences Initiative. "This study extends the techniques we developed using the microbiome to predict disease while a person is alive, and shows the microbiome can also provide useful information after death."

Knight was also part of a group of U.S. scientists who co-authored a recent Science paper calling for a nationwide Unified Microbiome Initiative.

For both the mouse and human cadavers, skin and soil microbes provided good accuracy in predicting time of death, with a roughly a two-to-four-day error estimate over a span of 25 days, said Knight. The team also demonstrated that bodies decomposing on soils modify the soil microbial communities substantially, allowing detection of a decomposing human body via the soil microbial community even if a body has been moved.

The accuracy of lock-step changes in the microbiota after death is shown to be on a par with blowflies, a current and popular forensic tool and which are attracted to vertebrate corpses where they lay eggs that develop as larvae in known time increments. But unlike the blowfly method -- which is of limited use by forensic scientists because of both cold seasons and corpse accessibility -- the new technique has no such constraints, said Metcalf.

Co-author Sibyl Bucheli of Sam Houston State said the new study also shows the importance vertebrate decomposition plays in the function of terrestrial ecosystems. While plant litter makes up by far the largest percentage of organic material on Earth's surface, decaying mammals are an important contributor in biological nutrient cycling.

Decomposition is a fundamental microbial function that plays a major role in how ecosystems work," said study co-author Sasha Reed at the U.S. Geological Survey in Moab, Utah. "This research adds a novel perspective showing how microbes from very different environments assemble and function in similar ways that allow for the production of natural fertilizer."
-end-
The study was funded in part by the National Institute of Justice, Office of Justice Programs in Washington, D.C., the National Institutes of Health, the National Human Genome Research Institute and the Templeton Foundation.

Contact:

Jessica Metcalf, 720-224-5522
jessicalmetcalf@gmail.com

Rob Knight, 858-246-1184
robknight@ucsd.edu

Jim Scott, CU-Boulder media relations, 303-492-3114
jim.scott@colorado.edu

Heather Buschman, UC San Diego media relations, 619-543-6163
hbuschman@ucsd.edu

University of Colorado at Boulder

Related Microbes Articles:

What can be learned from the microbes on a turtle's shell?
Research published in the journal Microbiology has found that a unique type of algae, usually only seen on the shells of turtles, affects the surrounding microbial communities.
Life, liberty -- and access to microbes?
Poverty increases the risk for numerous diseases by limiting people's access to healthy food, environments and stress-free conditions.
Rye is healthy, thanks to an interplay of microbes
Eating rye comes with a variety of health benefits. A new study from the University of Eastern Finland now shows that both lactic acid bacteria and gut bacteria contribute to the health benefits of rye.
Gut microbes may affect the course of ALS
Researchers isolated a molecule that may be under-produced in the guts of patients.
Gut microbes associated with temperament traits in children
Scientists in the FinnBrain research project of the University of Turku discovered that the gut microbes of a 2.5-month-old infant are associated with the temperament traits manifested at six months of age.
Gut microbes eat our medication
Researchers have discovered one of the first concrete examples of how the microbiome can interfere with a drug's intended path through the body.
Microbes can grow on nitric oxide
Nitric oxide (NO) is a central molecule of the global nitrogen cycle.
Microbes help make the coffee
When it comes to processing coffee beans, longer fermentation times can result in better taste, contrary to conventional wisdom.
Space microbes aren't so alien after all
A new Northwestern University study has found that -- despite its seemingly harsh conditions -- the ISS is not causing bacteria to mutate into dangerous, antibiotic-resistant superbugs.
Nutrient-recycling microbes may feel the heat
While microbial communities are the engines driving the breakdown of dead plants and animals, little is known about whether they are equipped to handle big changes in climate.
More Microbes News and Microbes Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Making Amends
What makes a true apology? What does it mean to make amends for past mistakes? This hour, TED speakers explore how repairing the wrongs of the past is the first step toward healing for the future. Guests include historian and preservationist Brent Leggs, law professor Martha Minow, librarian Dawn Wacek, and playwright V (formerly Eve Ensler).
Now Playing: Science for the People

#566 Is Your Gut Leaking?
This week we're busting the human gut wide open with Dr. Alessio Fasano from the Center for Celiac Research and Treatment at Massachusetts General Hospital. Join host Anika Hazra for our discussion separating fact from fiction on the controversial topic of leaky gut syndrome. We cover everything from what causes a leaky gut to interpreting the results of a gut microbiome test! Related links: Center for Celiac Research and Treatment website and their YouTube channel
Now Playing: Radiolab

The Flag and the Fury
How do you actually make change in the world? For 126 years, Mississippi has had the Confederate battle flag on their state flag, and they were the last state in the nation where that emblem remained "officially" flying.  A few days ago, that flag came down. A few days before that, it coming down would have seemed impossible. We dive into the story behind this de-flagging: a journey involving a clash of histories, designs, families, and even cheerleading. This show is a collaboration with OSM Audio. Kiese Laymon's memoir Heavy is here. And the Hospitality Flag webpage is here.