Tu Zhihao, Yumoto Isao
MOE Key Laboratory of Groundwater Circulation and Evolution & School of Water Resources and Environment, China University of Geosciences (Beijing).
Institute for Open and Transdisciplinary Research Initiatives, Osaka University.
Microbes Environ. 2025;40(3). doi: 10.1264/jsme2.ME24104.
In traditional indigo dyeing, water-insoluble indigo is anaerobically converted into soluble leuco-indigo via microbial reduction in alkaline dye suspensions, allowing its use as a fabric dye. Although various indigo-reducing bacteria have been isolated to date, culture-independent microbial community ana-lyses have suggested that bacteria belonging to uncultured clades also contribute to indigo reduction. Therefore, we aimed to isolate previously overlooked indigo-reducing bacteria using an unconventional culture method. We conducted enrichment cultures and single-colony isolation using a medium supplemented with sukumo, an indigo dye source derived from the composted leaves of indigo-containing plants, as the sole energy, carbon, and nitrogen sources. We isolated a previously uncultured bacterium belonging to the family Tissierellaceae, which had been predicted as a major indigo reducer in various indigo dyeing processes solely based on microbial community ana-lyses. The insoluble indigo-reducing activity of the Tissierellaceae isolate, strain TU-1 was significantly higher than that of known indigo-reducing bacteria. The addition of the culture supernatant of strain TU-1 enhanced the reduction of indigo powder by other indigo-reducing bacteria, with similar stimulatory effects to those of the insoluble electron mediator, anthraquinone. These results indicate that strain TU-1 possesses a high capacity for secreting electron mediators, conferring a significant reduction capacity for insoluble indigo. Further investigations, including the discovery of additional unknown indigo-reducing bacteria and the identification of the mediators they produce, will provide a more detailed understanding of the mechanisms underlying indigo reduction in practical dyeing processes.
在传统靛蓝染色中，水不溶性靛蓝在碱性染料悬浮液中通过微生物还原被厌氧转化为可溶性无色靛蓝，从而可作为织物染料使用。尽管迄今为止已分离出多种靛蓝还原菌，但基于培养的微生物群落分析表明，未培养分支中的细菌也有助于靛蓝还原。因此，我们旨在使用非常规培养方法分离先前被忽视的靛蓝还原菌。我们使用添加了 sukumo（一种源自含靛蓝植物堆肥叶片的靛蓝染料源）作为唯一能量、碳源和氮源的培养基进行富集培养和单菌落分离。我们分离出了一种先前未培养的属于蒂氏菌科的细菌，仅基于微生物群落分析，该细菌在各种靛蓝染色过程中被预测为主要的靛蓝还原剂。蒂氏菌科分离株 TU-1 的不溶性靛蓝还原活性明显高于已知的靛蓝还原菌。添加菌株 TU-1 的培养上清液可增强其他靛蓝还原菌对靛蓝粉末的还原作用，其刺激效果与不溶性电子介质蒽醌相似。这些结果表明，菌株 TU-1 具有分泌电子介质的高能力，赋予了对不溶性靛蓝显著的还原能力。进一步的研究，包括发现更多未知的靛蓝还原菌及其产生的介质的鉴定，将更详细地了解实际染色过程中靛蓝还原的潜在机制。
