Few described archaeal, and fewer bacterial, lineages thrive under salt-saturating conditions, such as solar saltern crystallizers (salinity above 30% w/v). They accumulate molar K⁺ cytoplasmic concentrations to maintain osmotic balance (‘salt-in’ strategy) and have proteins adaptively enriched in negatively charged acidic amino acids. Here we analysed metagenomes and metagenome-assembled genomes from geothermally influenced hypersaline ecosystems with increasing chaotropicity in the Danakil Depression. Normalized abundances of universal single-copy genes confirmed that haloarchaea and Nanohaloarchaeota encompass 99% of microbial communities in the near-life-limiting conditions of the Western-Canyon Lakes. Danakil metagenome- and metagenome-assembled-genome-inferred proteomes, compared with those of freshwater, seawater and solar saltern ponds up to saturation (6–14–32% salinity), showed that Western-Canyon Lake archaea encode the most acidic proteomes ever observed (median protein isoelectric points ≤4.4). We identified previously undescribed haloarchaeal families as well as an Aenigmatarchaeota family and a bacterial phylum independently adapted to extreme halophily. Despite phylum-level diversity decreasing with increasing salinity–chaotropicity, and unlike in solar salterns, adapted archaea exceedingly diversified in Danakil ecosystems, challenging the notion of decreasing diversity under extreme conditions. Metabolic flexibility to utilize multiple energy and carbon resources generated by local hydrothermalism along feast-and-famine strategies seemingly shapes microbial diversity in these ecosystems near life limits.

很少有描述古细菌和较少的细菌谱系在盐饱和条件下茁壮成长，例如日光盐碱结晶器（盐度高于 30% w/v）。它们积累摩尔 K⁺ 细胞质浓度以维持渗透平衡（“盐入”策略），并使蛋白质适应性地富集在带负电荷的酸性氨基酸中。在这里，我们分析了来自受地热影响的高盐生态系统的宏基因组和宏基因组组装的基因组，在达纳基尔洼地中，离液性增加。通用单拷贝基因的标准化丰度证实，盐古菌和纳米盐古菌在西部峡谷湖近乎生命限制的条件下包含 99% 的微生物群落。Danakil 宏基因组和宏基因组组装基因组推断的蛋白质组，与淡水、海水和太阳盐碱池的蛋白质组相比（盐度为 6-14-32%），表明西部峡谷湖古细菌编码有史以来观察到的最酸性蛋白质组（中位蛋白质等电点 ≤4.4）。我们确定了以前未描述的盐古细菌家族以及一个 Aenigmatarchaeota 家族和一个独立适应极端嗜盐的细菌门。尽管门水平的多样性随着盐度-离液性的增加而降低，并且与日光盐田不同，适应的古细菌在 Danakil 生态系统中非常多样化，挑战了在极端条件下多样性降低的概念。利用当地水热作用产生的多种能源和碳资源的代谢灵活性以及大饥荒策略似乎塑造了这些生态系统中接近生命极限的微生物多样性。