How did scientists discover uncultivated archaea in soils and oceans?

Scientists discovered uncultivated archaea in soils and oceans primarily through the use of culture-independent techniques. Because the majority of archaea cannot be grown in a laboratory setting, researchers bypass traditional culturing methods by isolating and analyzing nucleic acids—specifically DNA and RNA—directly from environmental samples.1

By extracting this genetic material directly from habitats like soil and seawater, scientists can identify and study these organisms without needing to isolate them in pure culture. This approach has revealed that archaea are ubiquitous and ecologically significant in diverse environments, including cold and temperate ecosystems where they were previously overlooked. For instance, these methods have shown that uncultivated Crenarchaeota are major ammonia-oxidizing organisms in soils and represent a significant portion of marine picoplankton. Similarly, culture-independent analysis has identified uncultivated Euryarchaeota in deep-sea sediments that play a critical role in the anaerobic oxidation of methane.1