Experimental tests of the competitive niche exclusion principle

The central ecological concept that we will apply is the competitive niche exclusion principle. This states that eco-systems are made up of niches of ecological opportunity. Niches are formed by available substrates, physical properties and species interactions. Species compete for niche space. The NEP states that each niche can be occupied by one species at one time. When all niches are filled, the system is stable and the combination of species determines overall system functionality. Over time and due to evolutionary processes such as species sorting, mutation and natural selection, species can specialize on their niche. We can use traditional fermented foods from Zambia as model system.
The products we study are dominated by lactic acid bacteria that generate an acidic environment. They are characterized by a mixed community of at least six to ten main microbes of lactic acid bacteria.


We can formulate and test predictions. (a) Long-term co-existence of the community is predicted to lead to niche specialization. Different selection pressures may lead to different outcomes of the process of niche specialization; each with some level of repeatability. (b) One could formulate a minimal species composition given the functionality of the ecosystem and potentially steer towards functionality. (c) Resilience against perturbation, for example the invasion of a new species. When all ecological space is filled, the system is predicted to be stable since no ecological opportunity exists for an invader, such as a pathogenic bacterium.


We can test these ideas experimentally using traditional fermented foods from Zambia that contain natural communities of lactic acid bacteria. Projects will focus on understanding the microbial dynamics during fermentation and how this is shaped by ecological forces such as variations in fermentation processing and variations in raw materials. In previous work we found that the microbial eco-systems in the products typically harbor six to ten different species. Here, we would like to construct various synthetic communities making several combinations asking what exact species interactions are essential for long-term ecological stability and overall functionality in terms of metabolic output (aroma profile) and which species composition maximize nutritional content. Further, we will test effects of adding additional species (pathogenic bacteria) to synthetic communities of increasing species complexity, testing the prediction that more complex systems will be more resilient to invasions. 

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We are open to applications for thesis projects! We have different thesis topics available, including projects with Molecular Techniques, microscopy and Phenotyping.

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