Abstract

• Decomposition processes of the mammalian corpses follow a predicted sequence and represent normal physiology of mammalian death. Decomposition contributes to nutrient recycling, energy flow and limiting biomass accumulation. • Decomposer species are always present upon death and emerge in diverse environments i.e. soil, sterile soil ,water, concrete basements etc. • Decomposer species may result from the microevolution of gut bacteria consistent with the observation that they have greater functional capacity and cellular complexity than gut bacteria and can survive in ammonium rich environment. • Decomposer species may represent the first demonstration of microevolution of microorganisms.

1. Introduction

Decomposition of the mammalian corpses creates a giant factory of microorganisms which convert proteins and lipids into foul smelling compounds (cadaverine, putrescine and ammonia) and contributes to nutrient recycling, energy flow, and limiting biomass accumulation.

The exact origin of microbial decomposer community remains unknown.

In this correspondence I review the literature on the origin of the decomposer species.

I investigate whether they are endogenous for our knowledge of the origin of decomposer species may help us understand the pathways involved in human degenerative disorders and may have clinical implications for burn wound and opportunistic infections.

2. Decomposer Species

When a mammal dies internal bacteria begin to grow before the rupture in the skin that allows air, microbes, and insects to enter, and bodily fluids to exit. A carcass releases large amounts of nitrogen mostly in the form of ammonia, as well as carbon, phosphorous, and other nutrients important for life and becomes a giant source of nutrients, and water ¹.

Noteworthy has been the observation that the process of decomposition follows a predicted sequence and the microbial communities change significantly during decomposition ^{1, 2}. Predicted functions of bacterial communities increase in relative abundance of genes for amino acid degradation and subsequent ammonia production ¹. It has been observed that the microbial decomposer community may emerge from multiple environments in which the decomposer organisms are often rare before decomposition begins ¹. The spectacular decomposer overgrowth in contrast to low abundance in nature seems to be paradoxical.

Of significance, It has been shown that vertebrate decomposition Is accelerated by soil microbes, yet it also occurs on sterile soil as mice placed on soil with intact microbial communities reach advanced stages of decomposition 2 to 3 times faster than those placed on sterile soil ³.

Metcalf and colleagues investigated the decomposition of mammalian corpses and observed predicted increases in genes related to nitrogen cycling and amino acid degradation including those required for the breakdown of lysine and arginine into the foul-smelling decomposition byproducts cadaverine and putrescine ¹. They also observed that ammonia rich fluids promote the growth of microorganisms with increased capacity for nitrogen cycling ¹. Bacterial communities increased in relative abundance of genes for amino acid degradation and subsequent ammonia production ¹.

A study of underwater decomposition of pig limbs enclosed in double plastic bags for 71 days revealed evidence of decomposition; ⁴. The decomposition process underwater in plastic bags consistent with the presence of the decomposer microbes support the possibility of their endogenous origin and makes it unlikely that the decomposers were imported species.

It has been proposed that the decomposer microorganisms may originate from soil. Yet this hypothesis suffers from major flaws: the decomposers emerge anywhere regardless of their environment. They have been found inside concrete structures ^{5, 6} buried in earth ⁷. In addition, the nature or type of soil makes no difference in their emergence ¹ and they also emerge in sterile soil ³; thus, it is reasonable to conclude that they evolve from the host bacteria, are endogenous and not foreign invaders.

3. Discussion

Diverse and converging evidence suggest the decomposer species are endogenous and they may evolve from the host bacteria.

Scavenger microbes contain genetic features endowed with an acquired capacity for nitrogen cycling and tolerance for survival without any genetic signs of increased nitrification rates. This seems to reflect a Darwinian observation: “death or life “conditions produce the decomposers capable to tolerate, consume and survive ammonia rich environments without getting distracted by less important earthly matters such as nitrification. In essence decomposer species may represent the first demonstration of evolution of microorganisms. The decomposer species may help us understand the pathways involved in the degenerative processes of human disorders and may have clinical implications for burn wound and opportunistic infections.

Acknowledgements

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Ethics approval

Not applicable because this study does not include human subjects or animals.

Conflict of interest

I confirm that I have no conflict of interest in the publication of my manuscript.

Consent for Publication

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Funding

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References