Oxygen Pulses: Engineering Microbial Communities to Combat Water Pollution

Emerging contaminants such as pharmaceutical residues and industrial chemicals pose a growing challenge to all life and are difficult to break down. Developing new wastewater treatments that are cost-effective and safe is essential. Complex electrochemical or light-treatment systems have been examined in the past, but these can be costly and not equipped for the broad range of contaminants modern wastewater systems encounter.

In this Marsden Fund-supported project, researchers led by Naresh Singhal look to nature to help solve this problem, using oxygen in combination with naturally existing microbial communities. This idea has been floated in the past, but Naresh’s team are challenging conventional wisdom around controlling oxygen flow. More specifically, they are experimenting with precisely controlled oxygen fluctuations that mimic the environmental variations seen in nature. This "oxygen modulation" strategy appears to enhance the microbial degradation of pollutants in ways that steady-state systems cannot achieve. It's a paradigm shift that could revolutionise how we manage wastewater and protect our precious water resources.

The research team is employing three distinct aeration strategies: Constant Aeration (as a baseline), Continuous Perturbation (with undulating oxygen levels), and Intermittent Perturbation (characterised by stark oxygen peaks and valleys). These variations trigger remarkable shifts in microbial metabolism, essentially "training" bacteria to become more efficient pollutant destroyers. "It's as if the challenge of adapting to fluctuating oxygen levels has unlocked hidden capabilities within these microscopic workhorses."

Pseudomonas putida, for example, can eliminate nearly half of the targeted organic pollutants under continuous oxygen fluctuations. Even more intriguing, intermittent oxygen conditions spurred bacteria to break down common pharmaceuticals like ibuprofen into entirely new products, hinting at the activation of novel degradation pathways (Figure 1).

Figure 1: Linking poorly degradable contaminants (showing <40% removal) to metabolic enzymes and microorganisms involved in degradation (Adapted with permission from Lyu et al. 2025)

This oxygen modulation approach offers a nature-aligned solution as communities worldwide grapple with water quality issues and resource scarcity. The research team is now striving to scale up their laboratory findings and adapt the technology for real-world treatment plants. Success could transform wastewater treatment from an energy-intensive necessity into a sustainable process that protects our environment and fosters a more circular economy (Figure 2).

Figure 2: Oxygen modulation alters cellular metabolism to shift protein, lipid, carbohydrate, free amino acid, and free fatty acid recovery compared to constant aeration (Adapted with permission from Zhou et al. 2025)

Additional information: Microbial metabolic enzymes, pathways and microbial hosts for co-metabolic degradation of organic micropollutants in wastewater

Additional information: Resource recovery from wastewater by directing microbial metabolism toward production of value-added biochemicals