News and Opinions  –  2017

Microbes – friend, foe or both?

2017-06-08

Life on Earth is arranged in ecosystems where all species are dependent on each other in intricate networks. We humans are also part of ecosystems, but we also harbour one in ourselves, an ecosystem of microbes called the human microbiome.

It is time to stop thinking about bacteria only as something bad that need to be exterminated and start thinking about ecology. We also need to develop new anti-infective therapies that do not also kill our microbiome when they kill the pathogenic microbes that make us sick.

Understanding ecosystems

Life on Earth is arranged in ecosystems where all species are dependent on each other in intricate networks. As an example, reintroduction of wolves in Yellowstone national park modified the behaviour of elk, although not their numbers, which in turn affected flowers and trees on riversides, leading to an increase in beavers who modified the rivers by building dams. This in turn led to better habitats for some songbirds, which increased in numbers. Who could have guessed that introducing wolves would increase the amount of flowers and songbirds?

In a similar manner, we humans are also a part of ecosystems. We modify them in many ways by hunting, agriculture and our industry. But we also harbour an ecosystem in ourselves, an ecosystem of microbes called the human microbiome.

A simplistic scheme for an ecological network could be construed of four types of species

Plants
Plants produce food for the herbivores from simple compounds in the soil and air with energy from the sun. If plants are lost, the source for food for all other species will be lost.

Herbivores
Plant eating animals eat plants for energy. The amount and species of herbivores affect the amount and species of plants in the system.

Carnivores
These animals get most of their energy from eating other animals, mainly herbivores.

Decomposers
Decomposers are insects, fungi, bacteria, but also larger scavenging animals such as vultures and crows can be put in this category. They live off dead plants and animals.

The human microbiome

This ecosystem, consisting mainly of bacteria, lives on our skin, in our nose, mouth and gut – on essentially all surfaces that are exposed to the outside world in one way or another. Most of these are of no harm to us or even beneficial in ways that science is just starting to understand. Actually, without these bacteria we would not get all necessary nutrients and be able to stay healthy.

Unfortunately, all bacteria are harmful when they end up in the wrong place, such as blood or urine. And some turn harmful when they get the opportunity to start growing in numbers. In some places in the human body these opportunists are being kept at an acceptable level by other species of good bacteria that limit their growth. Thus the opportunists cannot cause harm unless the beneficial bacteria diminish in numbers.

Humankind declaring a war we can never win

Due to a number of pathogenic bacteria that cause infections, almost all bacteria have historically been seen as guilty by association. Humankind has gone “to war” against all microbes. Cleaning, sterilising and using biocides and antibiotics have been the weapons of choice to apparently great success. And, these are indeed important tools against the fraction of bacteria that are indeed harmful. However, there are also drawbacks – not only have bacteria gained resistance to antibiotics, but our indiscriminate use of antibiotics has also caused disturbances called dysbiosis in our own microbiome. This dysbiosis is now suspected to play a part in many different diseases and disorders, ranging from gastrointestinal disorders via asthma and allergy through to neurological disorders.

The way forward

Now, with increasing rates of antibiotic resistance and emerging consequences of disturbing our microbiomes, it is time to lay down the arms and start thinking about ecology. Wherever antibiotics are used, there will be antibiotic resistance. It is not only a matter of spreading resistant strains through hospital wards or community outbreaks, but also spreading of the genes that cause resistance from one strain or species to another. It is time to learn the lesson that we cannot fight infections by killing bacteria indiscriminately. One way forward might be to view antibiotic susceptibility as a common good or limited resource and apply a sustainable development mind-set to it. Another way might be to develop new anti-infective therapies that do not also kill our microbiome when they kill the pathogenic microbes that make us sick.

It is time to stop viewing all bacteria, including our own as bad and rather embrace them as allies, while finding ways to treat the fraction of bacteria that do cause illness and deaths.

Learn more!

To learn more about our microbiome, read the new ReAct factsheet on the topic: “All You Wanted to Know About Microbes But Were Afraid to Ask… The Human Microbiome”.