Abstract
Several universal genomic traits affect trade-offs in the capacity, cost, and efficiency of the biochemical information processing that underpins metabolism and reproduction. We analyzed the role of these traits in mediating the responses of a planktonic microbial community to nutrient enrichment in an oligotrophic, phosphorus-deficient pond in Cuatro Ciénegas, Mexico. This is one of the first whole-ecosystem experiments to involve replicated metagenomic assessment. Mean bacterial genome size, GC content, total number of tRNA genes, total number of rRNA genes, and codon usage bias in ribosomal protein sequences were all higher in the fertilized treatment, as predicted on the basis of the assumption that oligotrophy favors lower information-processing costs whereas copiotrophy favors higher processing rates. Contrasting changes in trait variances also suggested differences between traits in mediating assembly under copiotrophic versus oligotrophic conditions. Trade-offs in information-processing traits are apparently sufficiently pronounced to play a role in community assembly because the major components of metabolism-information, energy, and nutrient requirements-are fine-tuned to an organism's growth and trophic strategy.
Highlights
Traits influencing the informational underpinnings of metabolism may be crucial to performance and community assembly, but ecologists have largely focused instead on the energetic and stoichiometric features of metabolism (Leal et al, 2017; Sibly et al, 2012; Sterner and Elser, 2002).For an organism to grow and reproduce rapidly, rates at every step of its metabolic network must be sufficiently high such that no single step is unduly rate-limiting, including the information processes that underpin biosynthesis and structure and regulate metabolic networks
We focus on a set of four information processing traits hypothesized to affect the ability of organisms to obtain the high maximum growth rates necessary for thriving in copiotrophic environments and/or reduce the energetic and resource requirements necessary to persist under nutrient-depleted conditions: aCC-BY-NC-ND 4.0 International license
The ratio of phosphorus to carbon (P:C) of seston biomass increased with fertilization (P =0.014, Fig 1A), providing additional evidence that organisms in the fertilized treatment had higher growth rates, since high P:C is associated with increased P-limited growth rate due to increased allocation to P-rich RNA required for augmented rates of biosynthesis (Elser et al, 2000)
Summary
Traits influencing the informational underpinnings of metabolism may be crucial to performance and community assembly, but ecologists have largely focused instead on the energetic and stoichiometric features of metabolism (Leal et al, 2017; Sibly et al, 2012; Sterner and Elser, 2002).For an organism to grow and reproduce rapidly, rates at every step of its metabolic network must be sufficiently high such that no single step is unduly rate-limiting, including the information processes that underpin biosynthesis and structure and regulate metabolic networks. In conjunction with research on the role of body size and other traits in influencing community assembly (e.g., Fukami et al, 2005; Litchman and Klausmeier, 2008; Okie and Brown, 2009; Roller and Schmidt, 2015), this body of work suggests an important community assembly role for traits associated with biological rates and efficiencies of resource use, growth, and reproduction It is unclear, whether the tradeoffs related to rates and costs of biochemical information processing are sufficiently pronounced to play an important role in evolutionary ecology and the assembly of communities, there are some promising indications (e.g., Roller et al., 2016)
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