Trade-Offs between Competition and Defense Specialists among Unicellular Planktonic Organisms: the "Killing the Winner" Hypothesis Revisited

Author(s)
Christian Winter, Thierry Bouvier, Markus Weinbauer, Tron Frede Thingstad
Abstract

A trade-off between strategies maximizing growth and minimizing losses appears to be a fundamental property of evolving biological entities existing in environments with limited resources. In the special case of unicellular planktonic organisms, the theoretical framework describing the trade-offs between competition and defense specialists is known as the "killing the winner" hypothesis (KtW). KtW describes how the availability of resources and the actions of predators (e. g., heterotrophic flagellates) and parasites (e. g., viruses) determine the composition and biogeochemical impact of such organisms. We extend KtW conceptually by introducing size-or shape-selective grazing of protozoans on prokaryotes into an idealized food web composed of prokaryotes, lytic viruses infecting prokaryotes, and protozoans. This results in a hierarchy analogous to a Russian doll, where KtW principles are at work on a lower level due to selective viral infection and on an upper level due to size-or shape-selective grazing by protozoans. Additionally, we critically discuss predictions and limitations of KtW in light of the recent literature, with particular focus on typically neglected aspects of KtW. Many aspects of KtW have been corroborated by in situ and experimental studies of isolates and natural communities. However, a thorough test of KtW is still hampered by current methodological limitations. In particular, the quantification of nutrient uptake rates of the competing prokaryotic populations and virus population-specific adsorption and decay rates appears to be the most daunting challenge for the years to come.

Organisation(s)
Functional and Evolutionary Ecology
External organisation(s)
Université Montpellier 2, Laboratoire d'Océanographie de Villefranche, University of Bergen (UiB)
Journal
Microbiology and Molecular Biology Reviews
Volume
74
Pages
42-57
No. of pages
16
ISSN
1092-2172
DOI
https://doi.org/10.1128/MMBR.00034-09
Publication date
2010
Peer reviewed
Yes
Austrian Fields of Science 2012
106022 Microbiology
Portal url
https://ucris.univie.ac.at/portal/en/publications/tradeoffs-between-competition-and-defense-specialists-among-unicellular-planktonic-organisms-the-killing-the-winner-hypothesis-revisited(56a7b5d0-be69-4885-a350-2ac5b866ba67).html