Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

A modified theory for the relationship between size and competitive ability

While molecular methods give information on microbial diversity in terms of number and type of co-existing species, they do not per se give an answer to the question of what controls the diversity and the success of particular species.

While traditional competition theory to a large extent has focussed on the importance of being small to be an efficient competitor for dissolved nutrients, we have shown that this is not the case if a non-limiting substrate can be used to increase size. In this case an osmotrop0h organism can gain competitive advantage from becoming large.

Since increasing size also has been postulated to protect from heavy predation pressure by microzooplankton, the result is a possible strategy that simultaneously optimizes competition and defense. The theory explains the success of osmotrophic microorganisms such as large bacteria under conditions with excess organic-C and diatoms under conditions with excess Si. The theory thus improves our ability to explain observed patterns in microbialø biodiversity.

Reported by

Department of Biology- University of Bergen
Jahnebakken 5
N-5020 Bergen
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