Microbial succession and enrichment of antibiotic resistance genes during algal-bacterial biofilm purification of aquaculture wastewater

Abstract

This study involved the establishment of algal-bacterial biofilms on the surface of carbon fiber-based artificial aquatic plants, utilizing algal-bacterial symbiosis for the purification of aquaculture wastewater. The algae-bacteria consortium exhibited strong photosynthetic activity, as indicated by the chlorophyll a + b content (0.918 ± 0.029 mg/g carbon fiber (CF)). Particularly, during the initial 7 days, algal-bacterial biofilm displayed robust water purification activity and capacity, with a significant reduction in total phosphorus (TP) of 39.44 % ± 2.43 % observed. The microbial community of the biofilm was diverse, primarily dominated by Proteobacteria, Cyanobacteria, Actinomycetota, and Planctomycetota. Among these, Proteobacteria were in the highest abundance ranging from 39.18 % to 40.61 %. Changes in Cyanobacteria, driven by nutrient level alterations, not only impacted species abundance but also posed a risk of promoting the spread of antibiotic resistance genes (ARGs). Through the complex interactions among biological communities, 15 types of ARGs have been enriched on the algal-bacterial biofilm, among which Multidrug, Bacitracin, Aminoglycoside, and Glycopeptid have a higher abundance. Contigs and network analysis indicate that Nannocystis, Sphingorhabdus, and Polynucleobacter are the key hosts and it is found that their abundance will increase during the purification of water quality by the algal-bacterial biofilm. This study highlighted the risk of ARG transmission in aquaculture effluent treatment with algal-bacterial biofilms.