In the spirit of Halloween, I thought of digging into the age-old question – is there life after death? Well, spiritually, I have no idea, but scientifically, the answer is yes. Hold on, now, before you get excited about potential zombie stories, let me clarify.

It all depends on how you define ‘life’. We know that after death, our internal organs remain intact for a brief period of time. The bacteria in our gut remain alive much longer, in fact, happily, as they suddenly have lots of extra food. A couple of years ago, microbiologist Peter Noble and his colleagues reported these microbes as the true zombies, who take over our internal organs postmortem (1). The team explored the types and time-profiles of bacteria colonizing different organs post death, revealing a possibility of using this information in forensics.

Recently, Noble and his team reported their studies on another fascinating aspect: activity of our genes after death (2). Genes are basically fragments of DNA that are responsible for the production of all kinds of proteins in our body. The term ‘gene transcription’ can be loosely explained as making copies of the gene; more number of copies results in more protein production, if the cell has enough energy. The authors systemically studied activities of about 1000 genes in mice (2 days) and zebrafish (4 days) after their death.

Interestingly, they found that some genes showed increased transcription after death. On categorizing functionally, they found that several of these genes were involved in stress and immune functions. Certain genes related to cancer were also found to be highly active. These results further emphasize why knowledge of the gene activity after death is important, especially when considering for organ transplants from deceased patients. Additionally, this information can also be used in forensics for an accurate estimate of the time of death, as shown in a complimentary report by the same authors (3).

In closing, Noble’s quote in Science summarizes the importance of these studies: “The headline of this study is that we can probably get a lot of information about life by studying death.”

Original publications

1. Can, Ismail, et al. “Distinctive thanatomicrobiome signatures found in the blood and internal organs of humans.” Journal of microbiological methods106 (2014): 1-7.
2. Pozhitkov, Alexander E., et al. “Thanatotranscriptome: genes actively expressed after organismal death.” bioRxiv (2016): 058305.
3. Hunter, M. Colby, Alexander Pozhitkov, and Peter Anthony Noble. “Accurate Predictions of Postmortem Interval Using Linear Regression Analyses of Gene Meter Expression Data.” bioRxiv (2016): 058370.