PT  - JOURNAL ARTICLE
AU  - Claire E. Price
AU  - Filipe Branco dos Santos
AU  - Anne Hesseling
AU  - Jaakko J. Uusitalo
AU  - Herwig Bachmann
AU  - Vera Benavente
AU  - Anisha Goel
AU  - Jan Berkhout
AU  - Frank J. Bruggeman
AU  - Siewert-Jan Marrink
AU  - Manolo Montalban-Lopez
AU  - Anne de Jong
AU  - Jan Kok
AU  - Douwe Molenaar
AU  - Bert Poolman
AU  - Bas Teusink
AU  - Oscar P. Kuipers
TI  - Glucose limitation in <em>Lactococcus</em> shapes a single-peaked fitness landscape exposing membrane occupancy as a constraint
AID  - 10.1101/147926
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 147926
4099  - http://biorxiv.org/content/early/2017/06/08/147926.short
4100  - http://biorxiv.org/content/early/2017/06/08/147926.full
AB  - A central theme in biology is to understand the molecular basis of fitness: which strategies succeed under which conditions; how are they mechanistically implemented; and which constraints shape trade-offs between alternative strategies. We approached these questions with parallel bacterial evolution experiments in chemostats. Chemostats provide a constant environment with a defined resource limitation (glucose), in which the growth rate can be controlled. Using Lactococcus lactis, we found a single mutation in a global regulator of carbon metabolism, CcpA, to confer predictable fitness improvements across multiple growth rates. In silico protein structural analysis complemented with biochemical and phenotypic assays, show that the mutation reprograms the CcpA regulon, specifically targeting transporters. This supports that membrane occupancy, rather than biosynthetic capacity, is the dominant constraint for the observed fitness enhancement. It also demonstrates that cells can modulate a pleiotropic regulator to work around limiting constraints.