Microbial Bioenergetics and Ecology Govern the Coupled Biogeochemical Cycling of Arsenic/Antimony and Macronutrients

Abstract

Arsenic (As) and antimony (Sb) are toxic metalloids whose biogeochemical cycles are strongly influenced by carbon (C), nitrogen (N), and sulfur (S) through microbially mediated coupled transformations. However, the mechanistic basis of these coupled processes remains poorly understood. In this Review, we synthesize current advances in the interconnected cycling and elucidate their thermodynamic and ecological foundations. Redox-sensitive As, Sb, C, N, and S species serve as electron donors and acceptors in microbial respiratory chains, and the combination of their redox half-reactions results in the coupled cycles. A redox-ladder framework delineates the theoretical electron flow and thermodynamically feasible coupling combinations. Many combinations have been observed in the environments-for instance, NO3– reduction to N2 coupled with As(III)/Sb(III) oxidation. Their realization also depends on microorganisms harboring key genes (e.g., aioA and arrA). The redox-ladder further predicts novel coupling processes, such as As(III)/Sb(III) oxidation coupled to N2O reduction to N2. We finally emphasize the need for quantitative biogeochemical models within global change scenarios. By integrating bioenergetic principles with microbial ecology, this Review provides a new conceptual framework for uncovering the linkages among elemental cycles, deepening our understanding of the mechanisms and environmental implications of As/Sb biogeochemical cycling coupled with macronutrients.