The pronoun ‘I’ is becoming obsolete

Don’t look now, but the pronoun “I” is becoming obsolete.  Recent microbiological research has shown that thinking of plants and animals, including humans, as autonomous individuals is a serious over-simplification.

A series of groundbreaking studies have revealed that what we have always thought of as individuals are actually “biomolecular networks” that consist of visible hosts plus millions of invisible microbes that have a significant effect on how the host develops, the diseases it catches, how it behaves and possibly even its social interactions.

It’s a case of the whole being greater than the sum of its parts“It’s a case of the whole being greater than the sum of its parts,” said Seth Bordenstein, associate professor of biological sciences at Vanderbilt University, who has contributed to the body of scientific knowledge that is pointing to the conclusion that symbiotic microbes play a fundamental role in virtually all aspects of plant and animal biology, including the origin of new species.

In this case, the parts are the host and its genome plus the thousands of different species of bacteria living in or on the host, along with all their genomes, collectively known as the microbiome.

(The host is something like the tip of the iceberg while the bacteria are like the part of the iceberg that is underwater: Nine out of every 10 cells in plant and animal bodies are bacterial. But bacterial cells are so much smaller than host cells that they have generally gone unnoticed.)

Microbiologists have coined new terms for these collective entities – holobiont – and for their genomes – hologenome. “These terms are needed to define the assemblage of organisms that makes up the so-called individual,” said Bordenstein.

In the article Host Biology in Light of the Microbiome: Ten Principles of Holobionts and Hologenomes published online Aug. 18 in the open access journal PLOS Biology, Bordenstein and his colleague Kevin Theis from the University of Michigan take the general concepts involved in this new paradigm and break them down into underlying principles that apply to the entire field of biology.

They make specific and refutable predictions based on these principles and call for other biologists to test them theoretically and experimentally.

“One of the basic expectations from this conceptual framework is that animal and plant experiments that do not account for what is happening at the microbiological level will be incomplete and, in some cases, will be misleading as well,” said Bordenstein.

The first principle they advance is that holobionts and hologenomes are fundamental units of biological organization.

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