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Over-fed bacteria make people sick

A research team suggests that inflammatory diseases are caused by an over-supply of food, and the associated disturbance of the intestine’s natural bacterial colonisation.

Since the end of the Second World War, along with the growing prosperity and the associated changes in lifestyle, numerous new and civilisation-related disease patterns have developed in today’s industrialised nations.

Examples of the so-called “environmental diseases” are different bowel inflammations like Crohn’s disease or ulcerative colitis. Common causes include disruptions to the human microbiome, i.e. the natural microbial colonisation of the body, and in particular of the intestine.

To date, scientists have explained this disrupted cooperation between host body and microbes with different hypotheses: for example, they postulated that excessive hygiene, the intensive use of antibiotics, or certain genetic factors permanently disrupt the microbiome, thus making people vulnerable to illnesses. However, these explanation attempts have so far been incomplete.

A team from the Collaborative Research Centre (CRC) 1182 “Origin and Function of Metaorganisms” at Kiel University (CAU) has now formulated a new and more comprehensive ecological-evolutionary theory on the development of environmental diseases. The Kiel researchers suggest that an unnatural and particularly comprehensive nutrient supply decouples bacteria from their host organisms, and thus destroys the delicate balance of the microbiome.

The starting point for the Kiel research team was the ecology of marine habitats: research on coral and algae dying off, and the associated effects on important ecosystems in the oceans, suggests that in addition to other factors such as climate change or overfishing, the nutrient conditions in the seawater may be the cause of the problem.

As soon as there is an oversupply of food due to human influences, bacteria living in a community with corals begin to decouple from their hosts. They then no longer feed off the metabolic products of the host, but prefer the richer nutrient supply of the surrounding waters. The balance of the coral microbiome is disrupted because of the exodus of its symbiotic partner, and diseases occur as a result.

The “over-feeding hypothesis” proposed by researchers from the Kiel CRC 1182, in close cooperation with the CAU Cluster of Excellence “Precision Medicine in Chronic Inflammation”, offers valuable approaches for further research, right through to potential transfer to future treatments: to date, scientists were particularly looking for ways to correct a disturbed microbiome through external interventions such as probiotics, i.e. the addition of certain types of helpful bacteria, or even faecal transplants to restore the balance.

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Posted on: May 22 2019

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