Dnitrification-synC1（plastic biofilm）

The specific procedure was as follows: The synthetic microbial community was resuspended in 7% salinity low-carbon 2216E medium to an OD600 of approximately 0.8, followed by the addition of 0 and 20 mg/L NO3--N. The culture was incubated at 25°C for 1 hour in a biochemical incubator, followed by centrifugation at 4500 r/min for 10 minutes to collect the bacterial pellets.

The centrifuge tubes were quickly frozen in liquid nitrogen. The samples were preserved with dry ice and shipped to Novogene Bioinformatics (Beijing, China). Metatranscriptomic sequencing was completed based on the Novaseq 6000 sequencing system (library insert size 350 bp, paired-end sequencing length 150 bp), generating 3 Gb of data for each sample.