Identifying Potential Mechanisms Enabling Acidophily in the Ammonia-Oxidizing Archaeon "Candidatus Nitrosotalea devanaterra".
Identifying Potential Mechanisms Enabling Acidophily in the Ammonia-Oxidizing Archaeon "Candidatus Nitrosotalea devanaterra".
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DOI：
10.1128/aem.04031-15
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发表时间：
2016-05
影响因子：
4.4
通讯作者：
Nicol GW
中科院分区：
文献类型：
--
作者：
Lehtovirta-Morley LE;Sayavedra-Soto LA;Gallois N;Schouten S;Stein LY;Prosser JI;Nicol GW
氨氧化是硝化作用的第一步，也是硝化反应的限速步骤，由土壤中两类不同的微生物控制：氨氧化古生菌(AOA)和氨氧化细菌(AOB)。AOA通常比AOB更丰富，并在酸性土壤中占主导地位。酸性条件下氨氧化的机理是一个长期存在的悖论。虽然在酸性土壤中经常检测到高氨氧化率，但在标准的实验室培养中，培养的氨氧化菌只能在近中性的pH下生长。虽然在实验室中已经证明了在低pH条件下中性AOB生长的一些机制，但这些机制在土壤中还没有得到证实，最近培养的专性嗜酸性氨氧化剂“Candidatus Nitrosotalea devanaterra”为观察到的高活性提供了一个更简洁的解释。对测序后的基因组、转录活性和脂肪含量进行分析。Nitrosotalea devanaterra“揭示了AOB以前提出的在低pH条件下生长的机制对酸性环境中古生菌的氨氧化不是必需的。取而代之的是，基因组表明“钙。Nitrosotalea devanaterra“包含编码预测的高亲和力底物获取系统和潜在的pH动态平衡机制的基因，中性AOA中没有这种机制。信使核糖核酸分析表明，编码上述动态平衡机制的候选基因均在嗜酸生长过程中表达，高效液相色谱-质谱仪(高效液相色谱-质谱仪)的脂谱分析表明，“钙”的膜脂。Nitrosotalea devanaterra“并不像在嗜中性的AOA中发现的那样，主要是棕榈酚。这项研究首次描述了一种嗜酸性氨氧化剂的基因组，并确定了使这一独特表型能够用于未来生化特性的潜在机制。
Ammonia oxidation is the first and rate-limiting step in nitrification and is dominated by two distinct groups of microorganisms in soil: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). AOA are often more abundant than AOB and dominate activity in acid soils. The mechanism of ammonia oxidation under acidic conditions has been a long-standing paradox. While high rates of ammonia oxidation are frequently measured in acid soils, cultivated ammonia oxidizers grew only at near-neutral pH when grown in standard laboratory culture. Although a number of mechanisms have been demonstrated to enable neutrophilic AOB growth at low pH in the laboratory, these have not been demonstrated in soil, and the recent cultivation of the obligately acidophilic ammonia oxidizer “Candidatus Nitrosotalea devanaterra” provides a more parsimonious explanation for the observed high rates of activity. Analysis of the sequenced genome, transcriptional activity, and lipid content of “Ca. Nitrosotalea devanaterra” reveals that previously proposed mechanisms used by AOB for growth at low pH are not essential for archaeal ammonia oxidation in acidic environments. Instead, the genome indicates that “Ca. Nitrosotalea devanaterra” contains genes encoding both a predicted high-affinity substrate acquisition system and potential pH homeostasis mechanisms absent in neutrophilic AOA. Analysis of mRNA revealed that candidate genes encoding the proposed homeostasis mechanisms were all expressed during acidophilic growth, and lipid profiling by high-performance liquid chromatography–mass spectrometry (HPLC-MS) demonstrated that the membrane lipids of “Ca. Nitrosotalea devanaterra” were not dominated by crenarchaeol, as found in neutrophilic AOA. This study for the first time describes a genome of an obligately acidophilic ammonia oxidizer and identifies potential mechanisms enabling this unique phenotype for future biochemical characterization.