We may not be so different from zombies when we die, after all. A new study analyzing bacterial communities involved in the decomposition of corpses illustrates how a cadaver becomes a living, thriving ecosystem for microorganisms.
The study, published recently in PLOS ONE, reveals that the type of bacteria embroiled in human decomposition can change over time.
Researchers from Sam Houston State University and Baylor College of Medicine – both in Texas – say that until now, little has been known about the bacterial diversity involved in breaking down a corpse.
While previous studies have been limited to a traditional approach of culturing bacteria, the team says that most of these microorganisms in the human body cannot be cultured in a lab experiment.
So, they remedied this problem by observing two human cadavers as they decomposed outside under natural conditions at the Southeast Texas Applied Forensic Science facility.
And rather than using traditional cultures, the researchers used a method involving gene sequencing to analyze the bacterial DNA.
A major advantage of this technique is that it enabled the team to measure bacterial genes in any region of the cadavers, allowing them to map out the entire microbial community at different points in the decomposition process.
The researchers note that the “early stages of decomposition are wet and marked by discoloration of the flesh and the onset and cessation of bacterially-induced bloat.”
During this stage, internal bacteria start digesting the intestines “from the inside out,” and the surrounding tissues are eventually completely consumed.
Though this is a gruesome thought, the researchers say the bloat stage can be helpful for forensic investigators, who use the timing of this stage to estimate the postmortem interval during investigations.
However, the researchers note that so little is known about the “bacterial basis of bloat,” which is why they investigated and catalogued the internal microbial communities of cadavers for the first time.
After observing the cadavers throughout the bloat stage, the researchers found that the bacterial communities among the two cadavers were different. They also found that within a single body, different regions had different bacterial communities, and these changed over the course of decomposition.
The team says this suggests that bacterial communities may follow specific patterns of change as a corpse moves through the varying stages of decomposition.
Aaron Lynne, one of the lead authors, says:
“This study is the first to catalogue bacteria present internally at the onset and end of the bloat stage of human decomposition. Ultimately, we hope to come up with a cumulative systems approach to look at decomposition in a way that might complement existing forensic models at determining the postmortem interval (time since death).”
The researchers add that although some of the species of bacteria observed in the cadavers were the same as those they had previously seen in culture-based-studies, many of them were new.
They conclude by noting that “a more comprehensive study is needed to further dissect the role of bacteria in human decomposition.”
Those dressing up as zombies this Halloween eve should be prepared to name which stage of decomposition they are in and which bacterial communities are feasting upon the chocolate they will undoubtedly consume.