Researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences, in collaboration with Qingdao University of Science and Technology and Zhangcun River Purification Plant, have developed a high-resolution strategy to identify and utilize naturally occurring phosphorus-removing microbes. Their findings were published in the journal Water Research.

Phosphorus runoff from agricultural and domestic sources is a primary driver of algal blooms and aquatic ecosystem degradation globally. To address this, wastewater treatment plants depend on phosphorus-accumulating organisms (PAOs), which absorb soluble phosphate and store it as intracellular polyphosphate. However, traditional cultivation methods often fail to reflect the real-world performance of these microbes, as their behavior in laboratory settings frequently differs from their activity in natural environments.

The research team addressed this discrepancy with a new platform called IMSCA (In-situ Metabolism-driven Sorting, Culture and Augmentation). This label-free approach combines single-cell Raman microspectroscopy, Raman-activated cell sorting, and single-cell cultivation, enabling researchers to screen and cultivate target microbes based on their actual metabolic behavior in wastewater—rather than in artificial laboratory media.

"IMSCA provides a direct window into microbial function in complex environments," said Prof. XU Jian, one of the study's corresponding authors. "It allows us to identify and cultivate the real performers—the microbes that are active in situ, where it matters most."

Notably, the researchers identified Micrococcus luteus CI5-8, a previously unrecorded PAO. Unlike well-known strains that require anaerobic conditions and store energy as polyhydroxyalkanoates (PHA), M. luteus CI5-8 functions under aerobic conditions, uses glycogen for energy storage, and does not perform denitrification. Though it showed weak performance in standard laboratory tests, this strain demonstrated strong phosphorus-removal capacity when evaluated directly in wastewater.

Capitalizing on its unique physiology, the research team reengineered a pilot-scale anaerobic-anoxic-aerobic (AAO) treatment reactor. When M. luteus CI5-8 was introduced into the aerobic stage of the process, phosphorus removal efficiency nearly doubled—from 45% to 89%—within just three days, despite fluctuations in influent conditions.

"This work highlights how many high-performing organisms have likely been overlooked because they do not thrive in pure culture in test tubes," noted Dr. JING Xiaoyan, the study's first author. "Our system not only uncovers these microbes but also provides guidance on how to identify and apply them in real-world operations."

The team believes that scRACS-Culture, the cultivation module within IMSCA, could be integrated into future wastewater treatment plants for live monitoring, customized strain deployment, and more intelligent process control. 

IMSCA platform uncovers "hidden champions" among a microbiota, dramatically enhancing phosphorus removal in wastewater. (Image by QIBEBT)