Martino E. Malerba

Nutrient utilization traits vary systematically with intraspecific cell size plasticity

We are grateful to the North Queensland Algal Identification and Culturing Facility (NQAIF), in particular Stan Hudson and Florian Berner. We are grateful to the Ecological Modelling Research Group at James Cook University, especially Dr Loic Thibaut for comments on modelling techniques and R codes. Also, thanks to the High Performance Computing team at James Cook University. We thank Dr Lyndon Llewellyn, Dr Christian Lonborg and Dr Catia Carreira for helpful advice. Finally, we thank A/Prof A. Martiny and an anonymous reviewer for detailed and constructive comments on the manuscript. This research was supported by AIMS@JCU (aims.jcu.edu.au), the Australian Institute of Marine Science (www.aims.gov.au), the Advanced Manufacturing Cooperative Research Centre (Project 2.3.4) and James Cook University (www.jcu.edu.au). The authors declare no conflict of interest.

Beneficial Mutations from Evolution Experiments Increase Rates of Growth and Fermentation

A major goal of evolutionary biology is to understand how beneficial mutations translate into increased fitness. Here, we study beneficial mutations that arise in experimental populations of yeast evolved in glucose-rich media. We find that fitness increases are caused by enhanced maximum growth rate (R) that come at the cost of reduced yield (K). We show that for some of these mutants, high R coincides with higher rates of ethanol secretion, suggesting that higher growth rates are due to an increased preference to utilize glucose through the fermentation pathway, instead of respiration. We examine the performance of mutants across gradients of glucose and nitrogen concentrations and show that the preference for fermentation over respiration is influenced by the availability of glucose and nitrogen. Overall, our data show that selection for high growth rates can lead to an enhanced Crabtree phenotype by the way of beneficial mutations that permit aerobic fermentation at a greater range of glucose concentrations.