RESUMO
In this study, the effects of different temperature transitions on the dynamics of antibiotic resistance genes (ARGs) and bacterial community were investigated during start-up of thermophilic anaerobic digestion (AD) of sewage sludge. Although two thermophilic reactors showed dissimilar removal efficiencies of ARGs in batch mode, both the removal efficiency and reduction patterns of ARGs were similar in continuous stirred tank reactor (CSTR) mode, resulting in significant reduction of the total sum of the relative abundance of ARGs. Using network analysis to explore the correlation between bacterial community and some specific ARGs revealed that composition of the bacterial community played a vital role in the fluctuations in the relative abundance of the antibiotic resistome, demonstrating that shaping the development of ARGs was facilitated by vertical gene transfer. To facilitate eliminating ARGs, minimizing their hosts which persist even under long-term operations is vital in thermophilic AD.
Assuntos
Antibacterianos , Esgotos , Anaerobiose , Resistência Microbiana a Medicamentos , Genes BacterianosRESUMO
Thermophilic aerobic digestion (TAD) was applied to further reduce ARGs and heavy metal resistance genes (HMRGs) as well as class 1 integrons (intI1) in sludge from anaerobic digestion (AnD). Unlike after AnD, there was no enrichment of ARGs, HMRGs and intI1 after TAD. Residual gene fractions of intI1 and total ARGs (sum of targeted ARGs) were 0.03 and 0.08, respectively. Two kinetic models (Collins-Selleck and first-order) described the decay patterns of targeted genes, revealing rapid removal of intI1 during TAD. After TAD, the relative abundance of human bacterial pathogens (HBPs) and the numbers of HBPs species decreased to approximately 68% and 64% compared to anaerobically digested sludge, respectively. Thus, TAD, subsequent to AnD, may possess high potential for reducing biological risks resulting from ARGs, HMRGs, intI1 and HBPs in sewage sludge.
