Lichtgedanken 03

S C HW E R P U N K T 15 03 | LICHT GEDANKEN those of all other organisms in the wor- ld. As a result, the number of microbial genes also far exceeds that of the higher organisms. They reproduce quickly and their genetic material is highly dynamic. Various different species of bacteria are able to exchange genes with one ano- ther, through what is known as hori- zontal gene transfer. This creates a large gene pool, which enables rapid changes in the genomes of various species. What can we then learn from this ex- tremely successful microscopic world? From microorganisms we can learn, for example, how to break down harm- ful substances in the environment or how to make use of microbial metabo- lic pathways in biotechnology. We can learn from them how to make natural products—active substances—to treat diseases, for instance. Above all, howe- ver, it is important for us to learn how microorganisms manage to communi- cate with each other and with their en- vironment, and how they succeed in maintaining their communities in a dy- namic equilibrium. Why is that important? Take human beings as an example. We live with around the same number of microorganisms as our body has cells. The question here is how do these microorganisms manage to live in such harmony with us that we provide them with a suitable habitat and they do not make us ill? They have learnt this over the course of evolution: they »com- municate« with each other and with our immune system using small chemical molecules, and in this way, they create an equilibrium. Our own bodies benefit from this in a variety of ways. We want to learn how this works, in order to be able to influence such microbial com- munities. Which ones, for example? The microflora in our intestines, for ex- ample. It is not only important for our digestion, but it is also decisive for a multitude of processes that affect our state of health and our well-being. If the flora is not in equilibrium, we become ill. There are millions of people who suf- fer from chronic bowel inflammation, for example, because their microflora is not in equilibrium. If we knew how to influence this flora—which microorga- nisms we should encourage and which ones we should inhibit—this would bring great relief to these patients. In addition, there are challenges that af- fect the whole of humanity, or even the entirety of life on Earth, such as climate change. Amajor problem in this context is the greenhouse gas methane, which is many times more potent than car- bon dioxide. And methane is generated exclusively by microorganisms that live in the stomachs of ruminants or in the soil. If we managed to manipulate the hordes of microbes currently producing huge amounts of methane, in such a way that methane production was stop- ped or at least reduced, we would have one less climate problem. It is not only scientists like you and your colleagues from universities and non-university research institutes who are concerned about microorganisms: at the 2017 G20 summit in Hamburg, the heads of state and government lea- ders of the most powerful countries in the world discussed the usual econo- mic and financial topics, but also tal- ked about diseases caused by microor- ganisms. Why is that? Because infectious diseases are a major and growing problem, here and around the world. In Germany alone, 60,000 people a year die of infectious disea- ses, an estimated 30,000 of them due to multiresistant microorganisms. This is a ticking time bomb. We are in a race against time, as new pathogens are de- veloping means of resistance, and that significantly faster than we can develop new active substances—new antibiotics. It is true that throughout human histo- ry there have been epidemics caused by microorganisms, which have depo- pulated whole areas. However, today the risk is much higher that infectious diseases could develop into pandemics, spreading extremely quickly across national borders and between conti- nents. With air travel, pathogens can go around the world in 36 hours. What are the most dangerous patho- gens that currently represent a threat to human health? These definitely include multiresistant strains of bacteria—of Klebsiella pneu- moniae or Pseudomonas aeruginosa , for example—against which there is no lon- ger any effective antibiotic. These bac- teria can trigger life-threatening lung diseases, especially in people with a we- akened immune system. There are also other multiresistant bacteria, and we are simply no longer able to treat such infections. There are additionally a few human-pathogenic fungi, such as yeast fungi or moulds, which cause invasive infections and against which there are as yet no effective drugs or treatment strategies. Recent data suggest that an intact microbiome helps to boost our natural defences against infections, but a micro- biome that does not function properly opens the doors to infections and other diseases. The human-microbe relationship the- refore appears to be quite ambivalent: are there good bacteria and bad bacte- ria? No, that would be too anthropomorphic a perspective. There is no question that it is important to be concerned about in- Microorganisms have formed and changed us in the course of our joint evolution. F E AT U R E