Systematic variation in the temperature dependence of bacterial carbon use efficiency

Abstract

Understanding the temperature dependence of carbon use efficiency (CUE) is critical for understanding microbial physiology, population dynamics, and community-level responses to changing environmental temperatures. Currently, microbial CUE is widely assumed to decrease with temperature. However, this assumption is based largely on community-level data, which are influenced by many confounding factors, with little empirical evidence at the level of individual strains. Here, we experimentally characterise the CUE thermal response for a diverse set of environmental bacterial isolates. We find that contrary to current thinking, bacterial CUE typically responds either positively to temperature, or has no discernible temperature response, within biologically meaningful temperature ranges. Using a global data-synthesis, we show that our empirical results are generalisable across a much wider diversity of bacteria than have previously been tested. This systematic variation in the thermal responses of bacterial CUE stems from the fact that relative to respiration rates, bacterial population growth rates typically respond more strongly to temperature, and are also subject to weaker evolutionary constraints. Our results provide fundamental new insights into microbial physiology, and a basis for more accurately modelling the effects of shorter-term thermal fluctuations as well as longer-term climatic warming on microbial communities.

Competition and resource depletion shape the thermal response of population fitness in Aedes aegypti

“…Furthermore, if the rate of biomass loss increases faster than any increase in biomass gain with temperature, the thermal optimum of (r m T opt ) may also shift downwards 21,22 . For the same reason, the range of temperatures over which r m is positive (the thermal niche width) may become narrower.…”

Integrating trait-based movement into mechanistic predictions of thermal performance

“…Growth rates are expected to be positive where energy gain outweighs energy loss. The energy loss rate of an individual increases exponentially with temperature (Gillooly et al 2001;Brown et al 2004) but exhibits negative curvature at high temperatures, indicating metabolic downregulation Gangloff et al 2015;Smith et al 2021). To compensate for increased energy loss from warming, ectotherms need to increase their energy gain through higher food intake (Pörtner et al 2006;Lurgi et al 2012; Movement constrains the fundamental ability to access spatially distributed or mobile resources (Bonte & Dahirel 2017;Goossens et al 2020) and is thus one of the major processes driving temperature-dependent trophic interactions (Dell et al 2014b;Schlägel et al 2020).…”

Latent functional diversity may accelerate microbial community responses to temperature fluctuations

“…This is compared to a calibration curve of known CO 2 concentrations, so the quantity of CO 2 produced by the culture can be determined, and thus the mass (in µ g) of carbon produced calculated. The biomass-specific respiration rate is then calculated using an equation that accounts for changes in biomass of the growing cultures over time [44]: Here, R tot is the total mass of carbon produced according to the MicroResp™ measurements, C 0 is the initial population biomass, µ is the previously calculated growth rate, and t is the experiment duration. ATP content of the cultures was measured using the Promega BacTiter-Glo reagent, which produces luminescence in the presence of ATP, proportional to the concentration of ATP.…”

“…1 for T = T pk . This model was fitted to each dataset using a standard non-linear least squares procedure [44].…”