Can humans survive without bacteria?

Without viruses there would be no corona, but also no life on earth

Viruses are the building blocks of life. You made human evolution possible. But they can also make us sick. “When viruses make you sick, people are usually responsible themselves. Because they disturbed the balance, ”says virologist Karin Moelling.

Moelling is a renowned, internationally highly regarded virologist. She has achieved significant achievements in AIDS and cancer research in particular and has received numerous awards for her life's work. She is still fascinated by the subject of her research.

There are more viruses than stars in the sky. There is no species in this whole world that does not have viruses. They are everywhere. In every living being, in the air, in the earth, in the sea.

Moelling explains in her book 'Superpower of Life. Travel to the amazing world of viruses ‘how important viruses are and that they don’t have to scare us - like the coronaviruses are now.

Living with viruses

Viruses are the largest biological population. It is common knowledge that they are distributed across our entire globe, that they colonize oceans, flora, fauna and also humans. But viruses are much closer to us than we long suspected. 2001 appeared in the magazine Nature a highly anticipated publication: the human genome had been deciphered. And what was found to everyone's surprise? Viruses! The human genome consists of at least 50 percent viruses, former viruses and virus-like elements. 50 percent is an estimate, it could also be a lot more, says Karin Moelling.

And that doesn't just affect us humans. The DNA of all living things on this planet consists of the DNA of viruses in varying proportions. How is that possible? Are the viruses our ancestors? The fact that viruses were the first living beings, the origin of life - that is still a hypothesis. A hypothesis that Dr. Moelling definitely represents. She is not alone in this. But there are also scientists who assume that bacteria were the first living things. Many even completely deny that the viruses are alive because they cannot multiply on their own. You need a host cell for this. At least that applies to the viruses occurring today. Billions of years ago it could very well have been different.

Virus and host

The relationship between virus and host cell can vary greatly - from the destruction of the cell to peaceful coexistence for mutual benefit. Viruses can remain inactive in a cell. Their reproduction then takes place through the natural division of the host cell. You do not harm the host. But they can also incorporate their own DNA into that of the host. If they integrate their DNA into the germ cells of their host, they are passed on from generation to generation. Certain mechanisms can reactivate the viruses and cause them to multiply in the cells. Or they remain, inscribed in the host's DNA, in the genome for all future. This process is called endogenizing. It is probably responsible for the fact that our DNA and that of all living things contain a large amount of viral DNA.

We are made up of viruses. However, that shouldn't scare us. On the contrary. The constant changes that viruses have brought about and continue to effect in our genome are part of our evolutionary history, our incarnation. Karin Moelling says: "Viruses are the engine of evolution."

Learn from viruses

She has two striking examples of what we learned from viruses. The first concerns our immune system. Once viruses have infected a cell, they do not want any competition there. Not even from their own species. They defend their host cell against other intruders, do not let them in or destroy them. That protects us from further pathogens. When they are endogenized, i.e. inscribed in our genetic make-up, this mechanism becomes part of our immune system. Viruses defend us. Against other viruses, but also against bacteria. Presumably all known immune systems were built by viruses.

A second example concerns human reproduction. Viruses have not only created our immune system, there are also viruses - not unlike HIV viruses - which have the ability to partially cancel out our immune system and thus the protection against exogenous cells. Because of this, we don't have to lay eggs or carry our offspring in a kind of kangaroo pouch. Due to the immune tolerance that is brought about, the embryo is not rejected by the mother's body and can develop until birth.

Necessity is the mother of invention

What was the evolutionary development aid of viruses like? Evolution does not necessarily mean higher development or an increase in complexity. It can also run in the opposite direction: from the complicated to the simple. If certain viruses are given ideal living conditions, they are simplified to what is essential for life: the ability to reproduce. That too is a principle of life. However, we humans never had ideal living conditions. On the contrary, we had to constantly face countless challenges, adapt to environmental conditions in order to survive as a species. Viruses have made this possible by constantly creating changes in our DNA that ultimately lead to new coping strategies. The tens of thousands of years of human and virus community history are written in our genes.

A viral disease is a great innovation boost for the genome, as a set of genes is added to the existing genome in one go. That brings something new. Especially since viruses are the greatest inventors.

Disturbed balances

Good viruses? Bad viruses? Neither nor. On the one hand, viruses are the engine of our evolution. On the other hand, infectious diseases, both bacterial and viral, are among the most common causes of death worldwide. But the fact that a virus becomes dangerous to its host is mostly due to a disturbed natural balance. The oceans are an example of this. Many algae contain viruses. When they multiply too much, the viruses in them are activated. They start to dissolve the algae and thus end algae plagues. The released components of the algae provide nutrients for other microorganisms. “These viruses regulate the population dynamics of algae. Algae and viruses have been interacting with one another for billions of years. "

There are innumerable types of viruses in humans that belong to our microbiome, the entirety of our natural microorganisms. But there are also pathogenic, i.e. potentially disease-causing viruses in us without us even noticing it. They only become active under certain conditions. A well-known example is the herpes virus, which many people carry. It only becomes active in stressful situations and shows its unpleasant appearance in the form of lip vesicles. We not only get sick through infection, but also when we have overworked ourselves, are hypothermic, and lose our balance.

Life-saving viruses

Karin Moelling is a restless researcher working in her field completely rises. After many other professional positions, from 1993 she was Professor of Virology and Director of the Institute for Medical Virology at the University of Zurich. In 2008 she retired. But she continued to work “all day and non-stop,” as she says. Your new research subject are the multi-resistant germs. They are a very dangerous problem, especially in our hospitals. Every year in Germany up to 20,000 people die from infections caused by multi-resistant bacteria. The cause is too frequent and unnecessary use of antibiotics. But antibiotics in animal feed and poor hygiene in hospitals are also part of it. There is a natural means by which pathogenic bacteria can be combated. And these are viruses!

Bacteria are also attacked by viruses, so-called phages. The discovery of phages goes back to 1917. A few years later, penicillin came into use and overtook them for the fight against bacterial diseases. But now the bacteriophages could be life-saving. Together with an international research group, Karin Moelling is currently developing a suitable therapy. And her new book on this subject is almost finished.

An evolutionary leap urgently needed

Dr. Moelling doesn't speculate. In her opinion, it has not yet been decided whether one can really speak of an increase. But she points out that viruses find ideal ways of spreading in the dense population of large cities and the enormous mobility. The path from virus to host is extremely short. Our countermeasures are accordingly, we cut off their paths through social isolation. Environmental factors such as air pollution could be an additional factor in the "success" of the coronaviruses. Now we will neither want nor be able to depopulate our cities. And globalization and mobility cannot simply be reversed. Other solutions have to be found. Man has to come up with something again. In the course of evolution, life has proven to be extremely resilient. However, nothing has ever been as destructive as man himself.

This text is based on an interview conducted in April this year and Karin Moelling's book “Superpower of Life. Travel to the amazing world of viruses ”, published in 2015 by C.H.Beck Verlag.

Become a member!

At Innovation Origins you can read the latest news about the world of innovation every day. We want it to stay that way, but we can't do it alone! Do you like our articles and would you like to support independent journalism? Then become a member and read our stories guaranteed to be ad-free.

About the author