The waning diversity of plants and animals have caused great concern yet with deep implications: Is such diversity in microbial life, such as viruses, under threat as well? If so, how fast is this decline, and in which direction?
According to a paper written by Dr. David S. Thaler of the University of Basel in Switzerland, "Is Global Microbial Biodiversity Increasing, Decreasing, or Staying the Same?", plant and animal diversity is going on a "clearly downward" path, and this comprises a "key issue of the Anthropocene."
Trend of Microbial Diversity Unknown
As for microbes, changes, he said, are completely unknown as there is no indication whether microbial diversity is increasing, decreasing, or staying as it is.
Dr. Thaler, who is also a guest investigator at Rockefeller University's Program for the Human Environment (PHE), stressed that evaluating plant and animal biodiversity requires counting of different species in a given timeframe, and then comparing them with a subsequent tally. After the assessment, they found out that some species have gone extinct, and many of them continue to exist but in lesser numbers, with about one million nearing extinction in a few decades.
The same method was utilized, for example, to monitor alterations in intestinal microbial diversity because of dietary changes.
Tracking the Change of Microbial Diversity
It would be impossible, Dr. Thaler said, to tally everything at various times to find out the direction of change in the diversity of microbes because of certain reasons:
- The unknown extent of present microbial biodiversity and a large share of the microbial world may exist in extreme, hard-to-reach environments.
- A possible "chicken and egg" paradox might be hard to unravel. Instituting a baseline sequence library may never be completed since new diversity is created more quickly than it is measured.
Dr. Thaler notes that the world is discovering hundreds of variants of the SARS-CoV-2 virus that causes COVID-19, which is among an estimated 10 billion kinds of evolving microbes.
He cites a video from the Harvard Medical School establishing the rapid pace of how bacteria can mutate to overpower higher doses and concentrations of antibiotics. And a recent study, "Escaping the 'Era of Pandemics': experts warn worse crises to come; offer options to reduce risk," revealed there are more than a million animal viruses, and half of them are possibly infectious to humans.
Potential repercussions in the course of the microbial evolution are not constricted to the development of pathogens that infect humans or the few species we rely on for food.
Changes in non-pathogenic microbial life might also affect the biosphere. The significance of complex communities of microorganisms, including about 10 billion types of microbes, is difficult to overemphasize. They sustain the Earth's habitability.
Importance of Microorganisms to the Earth's Climate and Atmosphere
Humanity relies on bacteria, fungi, archaea, and protists, microorganisms that recycle nutrients, purify water, decompose wastes, nurture plant growth, and make cheese and wine. And by transforming carbon dioxide to carbon to be kept in soils or the ocean depths (and doing the same for iron, manganese, sulfur, nitrogen, and more), microbes are essential to Earth's climate and atmosphere.
At present, heritable DNA sequence data is dominated by microbes, including viruses, Dr. Thaler said. He mentioned the intriguing possibility of macroscopically visible plants and animals comprising a shrinking amount of the biosphere's heritable information.
In addressing our need for more about our place in the universe of biological information, Dr. Thaler would consider DNA technologies as an option. How could current and future technologies help?
A focal point is on the "modulators and vectors" of microbial evolution. Other new approaches that might be enhanced include single molecule or single cell (DNA) sequencing.
Possible use of DNA to Measure Microbial Diversity
DNA barcodes and other sequencing-based approaches that are utilized to identify species of plants and animals and to gauge the amount of variation within species would lead to comparisons to measures of microbial biodiversity, Dr. Thaler said.
In the macroscopic and microbial world of visible plants and animals, a species may be identified as a cluster in sequence space, just like in terms of galaxies and stars, where species are galaxies, and individuals are stars.
It is thus increasingly difficult to catalog a complete list of plants and animals, having about 1,000 times as many microbes, and measure the changes. Visual images from research laboratories show the difficulty of directly counting them. Entire diverse and dense communities of microbes are contained in a few tens of a micrometer, which is the width of a human hair.
While Dr. Thaler's paper does not offer ways to solve this problem, it tries, however, to give a clear picture of the rate of change of microbial biodiversity as an important and interesting question that we need to answer.
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