Abstract
Many microbes live in habitats below their optimum temperature. Retention of metabolic heat by aggregation or insulation would boost growth. Generation of excess metabolic heat may also provide benefit. A cell that makes excess metabolic heat pays the cost of production, whereas the benefit may be shared by neighbors within a zone of local heat capture. Metabolic heat as a shareable public good raises interesting questions about conflict and cooperation of heat production and capture. Metabolic heat may also be deployed as a weapon. Species with greater thermotolerance gain by raising local temperature to outcompete less thermotolerant taxa. Metabolic heat may provide defense against bacteriophage attack, by analogy with fever in vertebrates. This article outlines the theory of metabolic heat in microbial conflict and cooperation, presenting several predictions for future study.
Highlights
Metabolic heat may play an important role in microbial conflict and cooperation
Does excess heat dissipate slowly enough that it can raise the rates of metabolic reactions and the growth rate of neighbors? Can excess heat be sufficiently concentrated to be used as a weapon that reduces the growth rate of relatively thermophobic competitors? What aspects of cellular aggregation and biofilm properties retain heat sufficiently to raise growth rate? How do changes in heat flow trade off against changes in the flow of other resources? How do larger-scale biophysical aspects of a habitat interact with smaller-scale intercellular processes to affect overall heat conductance?
The potential role of metabolic heat in microbial conflict and cooperation follows from basic observations and simple ideas
Summary
Metabolic heat may play an important role in microbial conflict and cooperation. Microbes often differ in their temperature optima (Alster et al, 2018). A microbe that raises the local temperature closer to its own optimum gains a growth advantage over relatively thermophobic competitors (Goddard, 2008). Aggregates may retain metabolic heat and gain a growth rate advantage (Tabata et al, 2013). Internal cells in an aggregate potentially benefit by generating excess heat, the energy cost reducing their own growth but stimulating faster growth among neighboring genetic relatives. Heat flow affects local temperature and the fitness of neighbors.
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