Aquatic environments of volcanic origin provide an exceptional opportunity to study the adaptations of microorganisms to early planet life conditions. Here, we characterized the prokaryotic communities and physicochemical properties of seepage sites at the bottom of the Poas Volcano crater and the Agrio River, two geologically related extremely acidic environments located in Costa Rica. Both locations hold a low pH (1.79–2.20) and have high sulfate and iron concentrations (Fe = 47–206 mg/L, SO₄²⁻ = 1170–2460 mg/L), but significant differences in their temperature (90.0–95.0 ºC in the seepages at Poas Volcano, 19.1–26.6 ºC in Agrio River) and in the elemental sulfur content. Based on the analysis of 16S rRNA gene sequences, we determined that Sulfobacillus spp. represented more than half of the sequences in Poas Volcano seepage sites, while Agrio River was dominated by Leptospirillum and members of the archaeal order Thermoplasmatales. Both environments share some chemical characteristics and part of their microbiota, however, the temperature and the reduced sulfur are likely the main distinguishing features, ultimately shaping their microbial communities. Our data suggest that in the Poas Volcano–Agrio River system there is a common metabolism but with specialization of species that adapt to the physicochemical conditions of each environment.

火山起源的水生环境为研究微生物对早期星球生命条件的适应提供了绝佳的机会。在这里，我们对位于哥斯达黎加的两个与地质有关的极端酸性环境Poas火山火山口和Agrio河底部的渗流点的原核生物群落和理化性质进行了描述。这两个地点的pH值都很低（1.79–2.20），并且硫酸盐和铁的浓度很高（Fe = 47–206 mg / L，SO ₄ ^2-  = 1170–2460 mg / L），但温度却有显着差异（90.0–在Poas火山的渗流中为95.0ºC，在Agrio河中为19.1–26.6ºC）和元素硫含量。通过对16S rRNA基因序列的分析，我们确定了Sulfobacillus spp。代表了Poas火山渗流点中一半以上的序列，而Agrio河则由钩端螺旋体和古细菌类热质体的成员主导。两种环境都具有某些化学特性和部分微生物区系，但是温度和还原的硫可能是主要的区别特征，最终塑造了它们的微生物群落。我们的数据表明，在波阿斯火山-阿格里奥河系统中，共有新陈代谢，但具有适应每种环境的理化条件的物种特化。