Microbiology Department, University of Tennessee, Knoxville, TN, United States of America.
Department of Biology, University of Naples "Federico II", Naples, Italy.
PLoS One. 2023 Aug 18;18(8):e0281277. doi: 10.1371/journal.pone.0281277. eCollection 2023.
Microbial communities in terrestrial geothermal systems often contain chemolithoautotrophs with well-characterized distributions and metabolic capabilities. However, the extent to which organic matter produced by these chemolithoautotrophs supports heterotrophs remains largely unknown. Here we compared the abundance and activity of peptidases and carbohydrate active enzymes (CAZymes) that are predicted to be extracellular identified in metagenomic assemblies from 63 springs in the Central American and the Andean convergent margin (Argentinian backarc of the Central Volcanic Zone), as well as the plume-influenced spreading center in Iceland. All assemblies contain two orders of magnitude more peptidases than CAZymes, suggesting that the microorganisms more often use proteins for their carbon and/or nitrogen acquisition instead of complex sugars. The CAZy families in highest abundance are GH23 and CBM50, and the most abundant peptidase families are M23 and C26, all four of which degrade peptidoglycan found in bacterial cells. This implies that the heterotrophic community relies on autochthonous dead cell biomass, rather than allochthonous plant matter, for organic material. Enzymes involved in the degradation of cyanobacterial- and algal-derived compounds are in lower abundance at every site, with volcanic sites having more enzymes degrading cyanobacterial compounds and non-volcanic sites having more enzymes degrading algal compounds. Activity assays showed that many of these enzyme classes are active in these samples. High temperature sites (> 80°C) had similar extracellular carbon-degrading enzymes regardless of their province, suggesting a less well-developed population of secondary consumers at these sites, possibly connected with the limited extent of the subsurface biosphere in these high temperature sites. We conclude that in < 80°C springs, chemolithoautotrophic production supports heterotrophs capable of degrading a wide range of organic compounds that do not vary by geological province, even though the taxonomic and respiratory repertoire of chemolithoautotrophs and heterotrophs differ greatly across these regions.
陆地地热系统中的微生物群落通常包含具有明确分布和代谢能力的化能自养生物。然而，这些化能自养生物产生的有机物在多大程度上支持异养生物仍然知之甚少。在这里，我们比较了中美洲和安第斯汇聚边缘（中央火山带阿根廷后弧）以及受羽流影响的冰岛扩张中心的 63 个泉水中宏基因组组装中鉴定出的肽酶和碳水化合物活性酶（CAZymes）的丰度和活性。所有的组装都包含了两个数量级的肽酶，而 CAZymes 则表明微生物更经常使用蛋白质来获取碳和/或氮，而不是复杂的糖。丰度最高的 CAZy 家族是 GH23 和 CBM50，而最丰富的肽酶家族是 M23 和 C26，这四种家族都能降解细菌细胞中的肽聚糖。这意味着异养群落依赖于自生的死细胞生物量，而不是异源的植物物质，来获取有机物质。在每个地点，参与降解蓝藻和藻类衍生化合物的酶的丰度都较低，火山地点有更多的酶降解蓝藻化合物，非火山地点有更多的酶降解藻类化合物。活性测定表明，这些酶类中的许多在这些样品中都是活跃的。高温地点（>80°C）的胞外碳降解酶具有相似的特征，无论其所在省份如何，这表明这些地点的二级消费者群体发育程度较低，这可能与这些高温地点地下生物圈的有限范围有关。我们的结论是，在<80°C 的泉水中，化能自养生物的产生支持能够降解范围广泛的有机化合物的异养生物，而这些有机化合物不受地质省份的影响，尽管化能自养生物和异养生物的分类和呼吸谱在这些地区有很大的差异。
