Work

Emergence of trait variability through the lens of nitrogen assimilation in Prochlorococcus

Year: 2019

Type: article

Abstract: ABSTRACT Intraspecific trait variability has important consequences for the function and stability of marine ecosystems. The marine cyanobacterium Prochlorococcus is a useful model system for understanding how trait variability emerges within microbial species: Its functional diversity is overlaid on measurable environmental gradients, providing a powerful lens into large-scale evolutionary processes. Here we examine variation in the ability to use nitrate across hundreds of Prochlorococcus genomes to better understand the modes of evolution influencing the allocation of ecologically important functions within microbial species. We find that nitrate assimilation genes are absent in basal lineages of Prochlorococcus but occur at an intermediate frequency that is randomly distributed within recently emerged clades. The distribution of nitrate assimilation genes within clades appears largely governed by vertical inheritance, stochastic gene loss, and homologous recombination among closely related cells. By mapping this process onto a model of Prochlorococcus’ macroevolution, we propose that niche-constructing adaptive radiations and subsequent niche partitioning set the stage for loss of nitrate assimilation genes from basal lineages as they specialized to lower light levels. Retention of these genes in recently emerged lineages has likely been facilitated by selection as they sequentially partitioned into niches where nitrate assimilation conferred a fitness benefit.

Source: eLife

DOI: 10.7554/elife.41043

Authors: Paul M. Berube, Anna Rasmussen, Rogier Braakman, Ramunas Stepanauskas, Sallie W. Chisholm

Institutions: Massachusetts Institute of Technology, Stanford University, Bigelow Laboratory for Ocean Sciences

Language: English

Topic: Microbial Community Ecology and Physiology

Subfield: Ecology

Field: Environmental Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,500

Funders: National Science Foundation, Simons Foundation, Gordon and Betty Moore Foundation