Temperature-responded microbial vanadium(V) reduction under a global warming scenario in aquifers

Microbially mediated vanadium (V) [V(V)] reduction is a key process for in situ remediation of vanadium-contaminated aquifers. In the context of global warming, the response of this process to temperature change remains poorly understood. This study investigated V(V) reduction dynamics and underlying mechanisms across a temperature gradient. V(V) reduction efficiency increased progressively with temperature rising, with 58.0 ± 3.16% at 4 °C and 67.3 ± 2.34% at 45 °C, respectively. V(V) was predominantly reduced to amorphous V(IV) precipitates. DNA stable isotope probing revealed V(V)-reducing genes narG and nirS were enriched in the heavy DNA fractions at both 4 °C and 45 °C. Metagenomic binning analysis revealed distinct distribution patterns of V(V)-reducing microorganisms under these two temperatures. At 4 °C, diverse V(V)-reducing microorganisms such as Stutzerimonas stutzeri accumulated, but their abundances diminished with increasing temperature to 45 °C. At 45 °C, V(V) reduction was primarily mediated by the enriched Delftia tsuruhatensis harboring narG. Metatranscriptomic and RT-qPCR analyses confirmed nirS and narG were more highly transcribed at 4 °C and 45 °C, respectively. Pure culture experiments corroborated the temperature response of V(V)-reducing bacteria and their functional genes. This study elucidates the temperature dependence of V(V) bioreduction and informs targeted bioremediation strategies under climate change.