L-norepinephrine induces ROS formation but alters microbial community composition by altering cellular metabolism

Catecholamines, such as L-norepinephrine (L-NE), are naturally present in the human gut and are discharged into the sewage. The bioactivity of L-NE can significantly alter the speciation and function of the microbial community by stimulating bacterial growth and producing H2O2. The accompanying changes in intracellular metabolism could significantly impact biological wastewater treatment processes, but they have remained unexplored. We investigate the alterations by L-NE and two other Catecholamines (Dopamine, and L-Dopa) to microbial consortia sourced from a dairy farm settling pond (FS) and the activated sludge of a municipal wastewater treatment plant (MS). We contrast the effect of the catecholamines on these mixed microbial communities with dextrose, a readily degradable substrate, and elevated levels of intracellular H2O2 through high dissolved oxygen (HDO) perturbations and exogenous applications of paraquat (PQ) and hydrogen peroxide (H2O2). The microbial community composition in different catecholamines was similar to the Dextrose treatment. However, there were significant changes in the PQ and H2O2 supplemented systems. In addition, the functional potential of the microbial communities with catecholamines and Dextrose were similar and provided insight into metabolic shifts from the control systems. While exogenous H2O2 increased the abundance of Rhodocyclaceae, Flavobacteriaceae and Chitinophagaceae and others, L-NE paralleled dextrose by increasing Pseudomonadaceae, Moraxellaceae, and Sphingobacteriaceae in the microbial consortia. A number of protein functions related to oxidoreductase, peroxidase, and catalase activities, ATP and FAD/FADH2 binding, nitrate reductase, and glutamate-ammonia ligase activity were differentially expressed by L-NE over dextrose, but many of the ROS-scavenging functions were overexpressed in the exogenous H2O2 treatment over L-NE. A proteome-constrained flux balance analysis showed that in comparison to dextrose, L-NE increased the fluxes of gluconeogenesis, glycolysis, oxidative stress metabolism, and glutamate metabolism. L-NE increases stress tolerance and microbial growth by upregulating the activities of oxidative stress mitigating enzymes (catalase and thioredoxin) and nitrogen assimilation activities (glutamine formation).