Microbial density-dependent viral dynamics and low activity of temperate phages in the activated sludge process

Metagenome sequencing reveals shifts in phage-associated antibiotic resistance genes from influent to effluent in wastewater treatment plants

Antibiotic resistance poses a significant threat to global health, and the microbe-rich activated sludge environment may contribute to the dissemination of antibiotic resistance genes (ARGs). ARGs spread across various bacterial populations via multiple dissemination routes, including horizontal gene transfer mediated by bacteriophages (phages). However, the potential role of phages in spreading ARGs in wastewater treatment systems remains unclear. This study characterized the core resistome, mobile genetic elements (MGEs), and virus-associated ARGs (vir_ARGs) in influents (Inf) and effluents (Eff) samples from nine WWTPs in eastern China. The abundance of ARGs in the Inf samples was higher than that in the Eff samples. A total of 21 core ARGs were identified, accounting for 38.70 %-83.70 % of the different samples. There was an increase in MGEs associated with phage-related processes from influents to effluents (from 12.68 % to 21.10 %). These MGEs showed strong correlations in relative abundance and composition with the core ARGs in the Eff samples. Across the Inf and Eff samples, 58 unique vir_ARGs were detected, with the Eff samples exhibiting higher diversity of vir_ARGs than the Inf samples. Statistical analyses indicated a robust relationship between core ARG profile, MGEs associated with phage-related processes, and vir_ARG composition in the Eff samples. Additionally, the co-occurrence of MGEs and ARGs in viral genomes was observed, ranging from 22.73 % to 68.75 %. This co-occurrence may exacerbate the persistence and spread of ARGs within WWTPs. The findings present new information on the changes in core ARGs, MGEs, and phage-associated ARGs from influents to effluents in WWTPs and provide new insights into the role of phage-associated ARGs in these systems.

Enhanced Bacterium-Phage Symbiosis in Attached Microbial Aggregates on a Membrane Surface Facing Elevated Hydraulic Stress

Phages are increasingly recognized for their importance in microbial aggregates, including their influence on microbial ecosystem services and biotechnology applications. However, the adaptive strategies and ecological functions of phages in different aggregates remain largely unexplored. Herein, we used membrane bioreactors to investigate bacterium-phage interactions and related microbial functions within suspended and attached microbial aggregates (SMA vs AMA). SMA and AMA represent distinct microbial habitats where bacterial communities display distinct patterns in terms of dominant species, keystone species, and bacterial networks. However, bacteria and phages in both aggregates exhibited high lysogenicity, with 60% lysogenic phages in the virome and 70% lysogenic metagenome-assembled genomes of bacteria. Moreover, substantial phages exhibited broad host ranges (34% in SMA and 42% in AMA) and closely interacted with habitat generalist species (43% in SMA and 49% in AMA) as adaptive strategies in stressful operation environments. Following a mutualistic pattern, phage-carried auxiliary metabolic genes (pAMGs; 238 types in total) presumably contributed to the bacterial survival and aggregate stability. The SMA-pAMGs were mainly associated with energy metabolism, while the AMA-pAMGs were mainly associated with antioxidant biosynthesis and the synthesis of extracellular polymeric substances, representing habitat-dependent patterns. Overall, this study advanced our understanding of phage adaptive strategies in microbial aggregate habitats and emphasized the importance of bacterium-phage symbiosis in the stability of microbial aggregates.

Biofilm metagenomic characteristics behind high coulombic efficiency for propanethiol deodorization in two-phase partitioning microbial fuel cell

Hydrophobic volatile organic sulfur compounds (VOSCs) are frequently found during sewage treatment, and their effective management is crucial for reducing malodorous complaints. Microbial fuel cells (MFC) are effective for both VOSCs abatement and energy recovery. However, the performance of MFC on VOSCs remains limited by the mass transfer efficiency of MFC in aqueous media. Inspired by two-phase partitioning biotechnology, silicone oil was introduced for the first time into MFC as a non-aqueous phase (NAP) medium to construct two-phase partitioning microbial fuel cell (TPPMFC) and augment the mass transfer of target VOSCs of propanethiol (PT) in the liquid phase. The PT removal efficiency within 32 h increased by 11-20% compared with that of single-phase MFC, and the coulombic efficiency of TPPMFC (11.01%) was 4.32-2.68 times that of single-phase MFC owing to the fact that highly active desulfurization and thiol-degrading bacteria (e.g., Pseudomonas, Achromobacter) were attached to the silicone oil surface, whereas sulfur-oxidizing bacteria (e.g., Thiobacillus, Commonas, Ottowia) were dominant on the anodic biofilm. The outer membrane cytochrome-c content and NADH dehydrogenase activity improved by 4.15 and 3.36 times in the TPPMFC, respectively. The results of metagenomics by KEGG and COG confirmed that the metabolism of PT in TPPMFC was comprehensive, and that the addition of a NAP upregulates the expression of genes related to sulfur metabolism, energy generation, and amino acid synthesis. This finding indicates that the NAP assisted bioelectrochemical systems would be promising to solve mass-transfer restrictions in low solubility contaminates removal.