A microbiome is a highly complex community of microorganisms that live together in a specific area, in the narrower sense in and on living organisms or plants. This community consists of a large number of different microorganisms, i.e. microscopically small bacteria, archaea, fungi, other single-celled organisms and viruses that work closely together. The microorganisms (also known as microbes or microbiota) are not recognisable to the naked eye, although they are present in very large numbers. The microbiome also includes their "action space", i.e. all the substances that these microorganisms produce, such as their genetic material, enzymes or short-chain fatty acids or enzymes, as well as their components, such as their genetic material (DNA).

The human microbiome is the best studied microbiome so far. It consists of a multitude of microorganisms that colonise all surfaces of the human body that are in contact with the outside world. For example, the genital area, the oral cavity, the skin and the nose harbour microbiomes that vary greatly in their composition. There are approximately 1.3 times more microbes (approx. 39 trillion) living in different areas of our body than we have our own body cells (approx. 30 trillion). Due to their small size, however, they only make up 1-3% of our body weight. The intestinal microbiome is a particular focus of attention in humans, as the microorganisms here play a vital role in digestion and nutrient absorption, contribute to the synthesis of vitamins, regulate the immune system and thus positively support the human organism. In general, a microbiome usually represents a fairly stable and balanced community. An imbalance in this community (dysbiosis) disrupts the complex interplay and is associated with various diseases such as intestinal disorders (e.g. Crohn's disease), autoimmune diseases, diabetes or even mental disorders (e.g. depression).

Microbiomes in the broader sense are not limited to living organisms, but can also include many other natural habitats, such as soil, water sources, air, but also artificially created spaces such as a biogas plant. The microbiome of the environment is crucial for the maintenance of ecosystem functions and plays an important role in nutrient cycling, pollutant degradation and plant health. For example, mycorrhizal fungi associated with plant roots supply important salts such as nitrate and phosphate to the plant.

Microbiome research is still a relatively young field of research. Thanks to the further development of technology (in particular the sequencing of large amounts of DNA) and analysis options ("OMICS technologies"), microbiomes can be analysed in ever greater detail. This not only identifies the individual microorganisms and thus clarifies which taxa make up a microbiome. Using the extensive OMICs methods, the genetic potential of the microbiome (genomics) and its activity (transcriptomics) can now also be analysed, and the metabolic processes (metabolomics) and expressed proteins (proteomics) can be identified. This acquired knowledge helps to understand the microbiome and the interrelationships of these complex communities and thus, if necessary, to actively intervene in them in order to improve or specifically control them. This can be used in personalised medicine or in agriculture, where it can be of great benefit. The aim of microbiome research is to better understand the interaction of microbes with each other and with their environment as well as their reactions to disturbances.

Literature to read and watch:

Wunderwaffe Mikrobiom - Kleine Helfer, große Wirkung (Youtube)

Darm-Mikrobiom: Aufbau, Funktion, Stärkung

Wie Bakterien unseren Körper beherrschen – Das Mikrobiom (Youtube)

Mikrobiom: Wie Mundbakterien die Gesundheit beeinflussen (Spektrum.de)

Why we need to worry about microbes when we send humans to Mars (Youtube)

Figure: Intestinal microbiome - coloured electron micrograph of a stool sample

© Text: Charlotte Julia Neumann, MedUni Graz, charlotte.neumann[at]medunigraz.at, Abbildung: Dagmar Kolb, MedUni Graz
Nutzung gem. CC 4.0