Wastewater treatment plants (WWTPs) often struggle with foaming in treatment tanks. Foaming, particularly from stable foams, can disrupt biological processes and often need costly chemicals to control. While there can be many causes of foaming, much of it is attributed to certain bacteria, the most common of which is Gordonia amarae. Recently, research published in Nature Communications shed light on a natural predator of Gordonia amarae, and, critically, reveals the host’s surprising mechanism of resistance. The study offers novel insights into microbial interactions within wastewater environments and presents a potential pathway for more sustainable foam management strategies.
Gordonia amarae and similar bacteria have sticky, hydrophobic outer layers of mycolic acid. It is these layers that are primarily responsible for stable foams. Candidatus Mycosynbacter amalyticus is one of many “dark matter” bacteria, a term used for microbes whose roles and interactions in wastewater environments are not yet understood. It is an “obligate necrotrophic parasite,” which means it specifically derives nutrients by killing its host. Mycosynbacter amalyticus attacks by attaching to the mycolic acid layer of Gordonia amarae and similar species to infect and consume the host. This parasitic action actually reduces the population of foam-causing Gordonia amarae, thereby mitigating the foaming issue.
However, over time Gordonia amarae can develop a resistance to these attacks. Using advanced electron cryo-tomography (CryoET) and whole-genome sequencing, the researchers pinpointed desirable mutations in the mycolic acid of the resistant Gordonia amarae strains. These mutations disrupt the structural integrity of the mycolic acid layer, making it harder for Mycosynbacter amalyticus to attach and kill. As a bonus, the reduced integrity also further mitigates foaming action.
This discovery not only reveals a fundamental aspect of host-parasite dynamics but also holds significant implications for wastewater management. By understanding how Gordonia amarae can become less susceptible to predatory bacteria, researchers may explore new avenues for controlling foaming without relying on costly chemical interventions. Scientists recognize, however, that these interactions took place in laboratory settings, so further research is needed in real world settings, where variables like pH, temperature, nutrient levels, and more are not stable or controllable. In addition, Gordonia amarae is just one of several types of foaming bacteria. Still, by understanding these microbial interactions, researchers are hopeful they could lead to the development of targeted biological solutions for more efficient and environmentally friendly wastewater treatment processes.
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