As plant / animal diversity declines, does microbial life change? Dangerous ‘deep ignorance’

Each color represents a different type of microbe. The white material in the nucleus represents the remains of human tongue cells around which microbes grow. Credit: Steven Wilbert, Gary Borisy, Forsyth Institute; Jessica Mark Welch, Marine Biology Laboratory

Alarms about the declining diversity of plants and animals cause a related problem with equally profound implications: Is the type of microbiological life, including viruses, changing? And if so, in what direction and how fast?

In a paper published today, David S. Thaler of the University of Basel, Switzerland, and a visiting researcher at the University of Rockefeller Program for the Human Environment (PHE), notes a well-documented trajectory of plant and animal diversity, “descending, representing” a key the question of the anthropocene “.

Whether changes are underway in the world of microbes – the tiniest gears in the functioning of the planet – “is a complete unknown. We have no idea whether global microbial diversity is increasing, decreasing or remaining,” says Dr. Thaler.

“Most scientific papers tell us about new facts. This is a different kind of work; it doesn’t answer anything, but asks a new question,” says Dr. Thaler.

“Socrates called ignorance of what we don’t know“ deep ignorance. ”This type of ignorance was also called“ unknown unknowns ”by former U.S. Secretary of Defense Donald Rumsfeld.Today’s article identifies what is (or has been since) a biological“ unknown unknown ”. “

Dr. Thaler points out that the assessment of plant and animal biodiversity involves counting different species over a period of time, and then comparing subsequent counting. In doing so, we learned that some species have recently become extinct, and many exist in smaller numbers, with an estimate that one million is threatened with extinction within a few decades.

The same approach was used, for example, to monitor changes in the diversity of intestinal microbes due to changes in diet.

Unfortunately, says Dr. Thaler, it may be impossible to “count them all at different times” to determine the direction of change in global microbial biodiversity because:

  • The extent of microbial current biodiversity is unknown, and much of the microbial world can exist in hard-to-reach, rare, or extreme environments — the deeper the depth, the less we know. Previous research has theoretically shown that the deep hot biosphere can contain most of the microbial diversity of our planet. Solving this problem could take 20 years before the deep biosphere and other hard-to-reach environments are sufficiently understood.
  • The possible paradox of ‘chicken and eggs’ may prove difficult to solve: establishing a library of baseline sequences may never be completed because new diversity is generated faster than measured. If some or all parts of microbial diversity increase rapidly, then research approaches may never catch up with this dynamic process.

Dr. Thaler says the world is finding hundreds of variants of the SARS-CoV-2 virus that causes COVID-19, one of approximately 10 billion microbial species, each developing in its own way.

As plant / animal diversity declines, does microbial life change?  Dangerous 'deep ignorance'

Each dot or thread is a bacterial cell and different colors indicate different types of bacteria. Larger, serrated ovals are unicellular algae called diatoms. Credit: Tabita Ramirez-Puebla and Jessica Mark Welch, Marine Biology Laboratory.

Dr. Thaler cites a video from Harvard Medical School documenting how quickly bacteria can mutate to overcome increasing concentrations of antibiotics. Meanwhile, a recent study also estimates that there are more than a million animal viruses, about half of which are potentially contagious to humans.

“Microbiological evolution is not always geared towards greater diversity; microbes can also become extinct, and the smallpox virus is an example,” he adds. “Countless other viruses and bacteria have probably also come and gone without us ever knowing they existed. Some microbes are specific in their associations to certain animals and plants. As these plants and animals become extinct, it seems likely that specialized microbes are associated they also disappeared. “

“The key thing is that in plants and animals we know that the current total trajectory of the Earth’s biosphere is towards a smaller number of species, but there is no comparable understanding of the total trajectory or detailed trajectory of the fine structure of microbial evolution.”

The possible implications on the trajectory of microbial evolution are not limited to the evolution of pathogens that attack humans or several species on which we depend for our food.

Changes in nonpathogenic microbial life can also have major implications for the biosphere. The importance of these complex communities of microorganisms – with estimates of up to 10 billion microbial species – is hard to overestimate: they maintain the Earth’s habit.

In 2011, scientists estimated that the Earth’s plant and animal species (or “macrobes”) numbered nearly 10 million, meaning that there are therefore 1,000 microbial species for each “macrobial” species, with the same macro-microbial ratio applicable to terrestrial and marine species.

Humanity depends on ecological services provided by bacteria, archaea, fungi and protists, which recycle nutrients, nurture plant growth, purify water, produce cheese and wine, and break down waste. And by converting atmospheric carbon dioxide back to carbon that will be stored in the soil or ocean depths (and similarly with nitrogen, sulfur, iron, manganese and others), microbes are key to the Earth’s atmosphere and climate.

Today globally, information about hereditary DNA sequences “is likely to be dominated by microbes, including viruses,” says Dr. Thaler. “It’s an intriguing possibility that macroscopically visible animals and plants may represent a declining share of hereditary biosphere data. We really don’t know.”

“However, we should probably know if we are at a loss in the biological information race and may even want to take practical steps to increase the information content ‘of our team.” There is also a purely intellectual interest in learning more about our place in the universe of biological information, perhaps analogous to our place in the expanding physical universe. “

This is a difficult question, but difficult does not mean impossible. He adds, “What approaches are at least starting to address it?”

As plant / animal diversity declines, does microbial life change?  Dangerous 'deep ignorance'

Each dot or thread is a bacterial cell and different colors indicate different types of bacteria. Larger, serrated ovals are unicellular algae called diatoms. Credit: Tabita Ramirez-Puebla and Jessica Mark Welch, Marine Biology Laboratory

DNA technologies are obviously a place to look. How can current technologies be applied and how can future developments help? Two approaches are suggested, says Dr. Thaler.

One of them is focusing on the “modulators and vectors” of microbial evolution, such as bacterial sex. Other new approaches that can be used include sequencing a single molecule or a single cell (DNA).

DNA bar codes and other sequence-based methods used to identify plant and animal species and to estimate the amount of variation within species “call for comparison with microbial biodiversity measures,” says Dr. Thaler.

“The clustering pattern seen in macroscopic life also seems to be a property of microscopic life forms in general. The details of the comparison are interesting. There could be general quantitative principles behind the truth that ‘life is bumpy.'”

In both the microbial and macroscopic worlds of visible plants and animals, a species can be considered a cluster “in sequence space,” which can be imagined in terms of stars and galaxies, where individuals are stars and species are galaxies.

Jesse Ausubel, director of PHE at Rockefeller University, sponsor of the study, says: “Linnaeus started his Systema Naturae in 1735, almost 300 years ago, and we still don’t have a complete list of plant and animal species he started cataloging. It won’t be easy to do something like that. with probably 1000 times more microbes and measure changes! “

Visual images from the laboratories of Gary Borisy (Forsyth Institute) and Jessica Mark Welch (Marine Biology Laboratory) show the difficulties of direct counting. A few tens of micrometers, the width of a human hair, spreads over entire diverse, populous microbial communities.

Dr. Thaler says this article does not offer “problem-solving protocols” but attempts to “frame the rate of change in microbial diversity as an interesting and potentially important issue on which progress is possible. I hope someone reading this paper will be encouraged to think about new approaches better. of those who propose themselves in it. “

Mr Ausubel added: “There is no agency yet that monitors the state of the microbial world, nor the World Wildlife Fund, nor nature conservation for microbes. Maybe one day we will soon realize and correct our neglect and raise our respect for the diversity of microbial life.”

The study reveals that microbial-plant interactions affect microbial responses to climate change

More information:
David S. Thaler. Is global microbial biodiversity increasing, decreasing or remaining the same? Boundaries in ecology and evolution (2021). DOI: 10.3389 / fevo.2021.565649

Provides Frontiers in Ecology and Evolution

Citation: As plant / animal diversity declines, does microbial life change? Dangerous ‘deep ignorance’ (2021, 19 April) retrieved 19 April 2021 from

This document is protected by copyright. Other than any fair dealing for the purpose of private study or research, no part may be reproduced without written permission. The content is available for informational purposes only.