Arsenic (As) is a metalloid present in the earth’s crust and widely distributed in the environment. Due to its high concentrations in the Andean valleys and its chemical similarity with phosphorus (P), its biological role in Andean Microbial Ecosystems (AMEs) has begun to be studied. The AMEs are home to extremophilic microbial communities that form microbial mats, evaporites, and microbialites inhabiting Andean lakes, puquios, or salt flats. In this work, we characterize the biological role of As and the effect of phosphate in AMEs from the Laguna Tebenquiche (Atacama Desert, Chile). Using micro X-ray fluorescence, the distribution of As in microbial mat samples was mapped. Taxonomic and inferred functional profiles were obtained from enriched cultures of microbial mats incubated under As stress and different phosphate conditions. Additionally, representative microorganisms highly resistant to As and able to grow under low phosphate concentration were isolated and studied physiologically. Finally, the genomes of the isolated Salicola sp. and Halorubrum sp. were sequenced to analyze genes related to both phosphate metabolism and As resistance. The results revealed As as a key component of the microbial mat ecosystem: (i) As was distributed across all sections of the microbial mat and represented a significant weight percentage of the mat (0.17 %) in comparison with P (0.40%); (ii) Low phosphate concentration drastically changed the microbial community in microbial mat samples incubated under high salinity and high As concentrations; (iii) Archaea and Bacteria isolated from the microbial mat were highly resistant to arsenate (up to 500 mM), even under low phosphate concentration; (iv) The genomes of the two isolates were predicted to contain key genes in As metabolism (aioAB and arsC/acr3) and the genes predicted to encode the phosphate-specific transport operon (pstSCAB-phoU) are next to the arsC gene, suggesting a functional relationship between these two elements.

砷 (As) 是一种存在于地壳中并广泛分布于环境中的准金属。由于其在安第斯山谷中的高浓度及其与磷 (P) 的化学相似性，已开始研究其在安第斯微生物生态系统 (AME) 中的生物学作用。AME 是极端微生物群落的家园，这些微生物群落形成微生物垫、蒸发岩和栖息在安第斯湖、puquios 或盐滩的微生物群。在这项工作中，我们表征了 As 的生物学作用和磷酸盐在 Laguna Tebenquiche（智利阿塔卡马沙漠）中的 AME 中的作用。使用微 X 射线荧光，绘制了微生物垫样品中 As 的分布图。从在砷胁迫和不同磷酸盐条件下培养的微生物垫的富集培养物中获得分类学和推断的功能特征。此外，对砷具有高度抗性并能够在低磷酸盐浓度下生长的代表性微生物被分离出来并进行了生理学研究。最后，分离出的基因组Salicola sp. 和Halorubrum sp。测序以分析与磷酸盐代谢和砷抗性相关的基因。结果表明 As 是微生物垫生态系统的关键组成部分：(i) As 分布在微生物垫的所有部分，与 P (0.40%) 相比，As 占微生物垫的显着重量百分比 (0.17%)；(ii) 低磷酸盐浓度极大地改变了在高盐度和高 As 浓度下培养的微生物垫样品中的微生物群落；(iii) 从微生物垫中分离出的古细菌和细菌对砷酸盐（高达 500 mM）具有高度抗性，即使在低磷酸盐浓度下；(iv) 预测这两个分离株的基因组包含砷代谢的关键基因（aioAB和arsC / acr3 ) 和预测编码磷酸盐特异性转运操纵子 ( pstSCAB-phoU ) 的基因与arsC基因相邻，表明这两个元件之间存在功能关系。