Inside the guts of the city: urbanization reduces gut microbiota diversity in house sparrows

Date: 25 September 2017

Introduction: The effects of urbanisation extend as far as the microbiome of house sparrows, a new study shows. This has potentially far-reaching implications for the fitness of the birds.

There is increasing evidence that the fitness of individual organisms cannot be considered independently from the bacteria their body hosts. That gut microbiome is important for digestion processes, is quite common knowledge. But recently a surge of new studies shows that the relation goes quite a lot deeper. Immunity, growth and reproduction, behaviour: all these essential aspects of the life of humans and animals can directly be affected by the microbiome that inhabits their bodies.

Yet, while we know that microbiome is crucial for multiple aspects of animal  and plant life, we know very little about how human disturbances potentially affect the microbiome. That is why researchers from UGent (Department of Biology and Department of Pathology), UAntwerp (Global Change Ecology Centre, research group Evolutionary Ecology) and Université Paul Sabatier in Toulouse teamed up to study whether increasing urbanisation of the landscape potentially affects the microbiome of the house sparrow. Research was performed around Antwerp, Gent and Leuven.

The new study was performed in a well-known bird: the house sparrow (Photo: Adamo).

Aimeric Teyssier, main researcher involved in the study: “As far as we know, no other study has studied the effect of increasing urbanisation on animal microbiome. In the framework of a larger study on the effects of urbanisation, we therefore investigated the gut microbiome in a wild bird, the house sparrow, along a gradient going from rural to strongly urbanized.”

The researchers identified the bacterial communities living in the birds’ intestines using next-generation sequencing techniques. Aimeric: “Birds from urban areas hosted less diverse microbial communities with different species composition, compared to their rural counterparts.”

An interesting observation was that the microbiome in the city birds was better at detoxifying potentially harmful “xenobiotics” in the gut, associated to the increased pollution in the city. Aimeric: “This indicates that the microbiome might play an essential role in the adaptation of the birds to the city. However, while this is a positive aspect, multiple other more negative implications are associated with the reduced microbiome diversity. The birds can become less effective in their food digestion and loose immunity against potentially fatal diseases.  We think that the reduced gut biodiversity is an important aspect to consider in the recent declines house sparrows have experienced in several cities.”

The study was published in the scientific journal “Science of the Total Environment”.