Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.
Singapore Centre for Environmental Life Sciences Engineering, Interdisciplinary Graduate Programme, Nanyang Technological University, Singapore, Singapore.
Microbiol Spectr. 2022 Dec 21;10(6):e0184522. doi: 10.1128/spectrum.01845-22. Epub 2022 Nov 29.
Ammonia-oxidizing archaea (AOA) can oxidize ammonia to nitrite for energy gain. They have been detected in chloraminated drinking water distribution systems (DWDS) along with the more common ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). To date, no members of the AOA have been isolated or enriched from drinking water environments. To begin the investigation of the role of AOA in chloraminated DWDS, we developed a selective approach using biofilm samples from a full-scale operational network as inoculum. A Nitrososphaera viennensis-like AOA taxon was enriched from a mixed community that also included Nitrosomonas-like AOB while gradually scaling up the culture volume. Dimethylthiourea (DMTU) and pyruvate at 100 μM were added to promote the growth of AOA while inhibiting AOB. This resulted in the eventual washout of AOB, while NOB were absent after 2 or 3 rounds of amendment with 24 μM sodium azide. The relative abundance of AOA in the enrichment increased from 0.2% to 39.5% after adding DMTU and pyruvate, and further to 51.6% after filtration through a 0.45-μm pore size membrane, within a period of approximately 6 months. Chloramination has been known to increase the risk of nitrification episodes in DWDS due to the presence of ammonia-oxidizing microorganisms. Among them, AOB are more frequently detected than AOA. All publicly available cultures of AOA have been isolated from soil, marine or surface water environments, meaning they are allochthonous to DWDS. Hence, monochloramine exposure studies involving these strains may not accurately reflect their role in DWDS. The described method allows for the rapid enrichment of autochthonous AOA from drinking water nitrifying communities. The high relative abundance of AOA in the resulting enrichment culture reduces any confounding effects of co-existing heterotrophic bacteria when investigating the response of AOA to varied levels of monochloramine in drinking water.
氨氧化古菌（AOA）可以将氨氧化为亚硝酸盐，以获取能量。它们已在加氯饮用水分配系统（DWDS）中与更为常见的氨氧化细菌（AOB）和亚硝酸盐氧化细菌（NOB）一起被检测到。迄今为止，尚未从饮用水环境中分离或富集到 AOA 的成员。为了开始研究 AOA 在加氯 DWDS 中的作用，我们使用来自全尺寸运行网络的生物膜样本作为接种物，开发了一种选择性方法。从包含类似于 Nitrosomonas 的 AOB 的混合群落中，逐渐扩大培养体积，富集了一种类似于 Nitrososphaera viennensis 的 AOA 分类群。添加 100 μM 的二甲基硫脲（DMTU）和丙酮酸盐可促进 AOA 的生长，同时抑制 AOB。这导致 AOB 最终被冲洗掉，而在经过 2 或 3 轮添加 24 μM 叠氮化钠后，NOB 就不存在了。在添加 DMTU 和丙酮酸盐后，富集物中 AOA 的相对丰度从 0.2%增加到 39.5%，在用 0.45-μm 孔径的膜过滤后进一步增加到 51.6%，这一过程大约持续了 6 个月。由于氨氧化微生物的存在，加氯已被认为会增加 DWDS 中硝化作用的风险。其中，AOB 的检出频率高于 AOA。所有可公开获得的 AOA 培养物均从土壤、海洋或地表水环境中分离得到，这意味着它们都是 DWDS 的异源生物。因此，涉及这些菌株的单氯胺暴露研究可能无法准确反映它们在 DWDS 中的作用。所描述的方法允许从饮用水硝化群落中快速富集本土 AOA。在所得富集培养物中 AOA 的相对高丰度降低了在研究 AOA 对饮用水中单氯胺不同水平的反应时，与共存异养细菌相关的任何混杂影响。
