Insight into the Reduction of Antibiotic Resistance Genes and Changes in Associated Microbial Communities and Metabolic Functional Genes during BALO-Induced Sludge Biolysis Pretreatment

Wastewater treatment plants are recognized as “hotspots” for the emergence and dissemination of antibiotic resistance genes (ARGs). Bdellovibrio-and-like organisms (BALOs), as obligatory predatory bacteria, simultaneously remove ARGs when lysing sludge for dewaterability improvement. Quantitative polymerase chain reaction (qPCR) results revealed the significant removal of typical ARGs and mobile genetic elements (MGEs). Then, metagenomic analysis further indicated that the relative abundances of 61.5 and 63.3% of the detectable ARGs and MGEs gradually decreased during the 36 h sludge biolysis process, with more than half of the ARG and MGE subtypes achieving their highest degradation rates at the optimal reaction time of 16 h, ranging from (32.4 ± 0.5) to 100%. The main potential antibiotic-resistant bacteria as BALOs’ hosts were probably within the seven genera, Rhodoferax, Hydrogenophaga, Lutimaribacter, Variovorax, Ideonella, Xenophilus, and Rubivivax, whose lysis would contribute to ARG degradation in the sludge. Moreover, the enhanced proteases, nucleases, and hydrolases encoded genes’ expressions highly emphasize the importance of replication and repair, nucleotide, energy, and amino acid metabolism activities for ARG degradation during the biolysis process. Consequently, the application of BALOs in sludge biolysis could limit the spread of ARGs in the environment.