We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
Mechanistic insights into superior biofilm formation with heterotrophic nitrification-aerobic denitrification bacteria under polypropylene microplastic stress
Summary
Microplastics are known to mess with the helpful bacteria that treat wastewater and remove nitrogen pollution, but this study found that using a special type of bacteria to "seed" water treatment systems made them much more resistant to this disruption. This matters because as plastic pollution keeps growing, protecting the microbial communities that clean our water is essential for keeping waterways—and the water we eventually drink—free of excess nitrogen pollution.
Microplastics may disturb microbial activity and biofilm development in biological wastewater treatment systems, yet the response of three-dimensional rotating biological contactor start-up biofilms to polypropylene microplastic stress remains unclear. This study evaluated a biofilm initiation strategy using heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria (H-3D-RBCs) and compared it with activated sludge-inoculated systems (A-3D-RBCs) under polypropylene microplastic (PP-MP) exposure. H-3D-RBCs showed superior resistance to PP-MP disturbance, with total nitrogen removal decreasing by only 14 %, compared with an approximately 60 % decline in A-3D-RBCs. Respiratory activity inhibition remained below 15 % in H-3D-RBCs but exceeded 90 % in A-3D-RBCs. 16S rRNA gene sequencing showed that PP-MP reduced species richness and diversity in A-3D-RBCs and was associated with a > 90 % loss of core denitrifying genera, including Corynebacterium and Pseudoxanthomonas, whereas H-3D-RBCs maintained community stability and enriched Pseudoxanthomonas to 13.8 %. Metagenomic analysis indicated that PP-MP impaired nitrification and denitrification potential in A-3D-RBCs, as reflected by decreased genes encoding AMO and HAO, a 51.78 % decrease in nosZ abundance, and enhanced dissimilatory nitrate reduction to ammonium (DNRA), which likely intensified competition with denitrification and promoted nitrogen conversion to ammonia. In contrast, H-3D-RBCs suppressed DNRA and maintained high nosZ abundance. Untargeted metabolomics further showed that PP-MP was associated with metabolic disorders in A-3D-RBCs, especially disruptions in alanine, aspartate, and glutamate metabolism and arginine biosynthesis, whereas H-3D-RBCs preserved these key nitrogen metabolic processes. Overall, this study identifies key vulnerabilities of nitrogen-removal biofilms under PP-MP disturbance and provides multi-omics evidence to support the development of microplastic-resistant biofilm wastewater treatment systems.