Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo, Piracicaba, São Paulo, Brazil.
Federal University of Ceará, Fortaleza, Ceará, Brazil.
Environ Pollut. 2021 Feb 15;271:116374. doi: 10.1016/j.envpol.2020.116374. Epub 2020 Dec 22.
Antibiotic residues in the environment are concerning since results in dispersion of resistance genes. Their degradation is often closely related to microbial metabolism. However, the impacts of soil bacterial community on sulfadiazine (SDZ) dissipation remains unclear, mainly in tropical soils. Our main goals were to evaluate effects of long-term swine manure application on soil bacterial structure as well as effects of soil microbial diversity depletion on SDZ dissipation, using "extinction dilution approach" and C-SDZ. Manure application affected several soil attributes, such as pH, organic carbon (OC), and macronutrient contents as well as bacterial community structure and diversity. Even minor bacterial diversity depletion impacted SDZ mineralization and non-extractible residue (NER) formation rates, but NER recovered along 42 d likely due to soil diversity recovery. However, this period may be enough to spread resistance genes into the environment. Surprisingly, the non-manured natural soil (NS-S1) showed faster SDZ dissipation rate (DT = 2.0 versus 21 d) and had a great number of bacterial families involved in major SDZ dissipation pathways (mineralization and mainly NER), such as Isosphaeraceae, Ktedonobacteraceae, Acidobacteriaceae_(Subgroup_1), Micromonosporaceae, and Sphingobacteriaceae. This result is unique and contrasts our hypothesis that long-term manured soils would present adaptive advantages and, consequently, have higher SDZ dissipation rates. The literature suggests instantaneous chemical degradation of SDZ in acidic soils responsible to the fast formation of NER. Our results show that if chemical degradation happens, it is soon followed by microbial metabolism (biodegradation) performed by a pool of bacteria and the newly formed metabolites should favors NER formation since SDZ presented low sorption. It also showed that SDZ mineralization is a low redundancy function.
环境中的抗生素残留令人担忧，因为它们会导致耐药基因的传播。它们的降解通常与微生物代谢密切相关。然而，土壤细菌群落对磺胺嘧啶（SDZ）降解的影响尚不清楚，主要是在热带土壤中。我们的主要目标是评估长期猪粪施用对土壤细菌结构的影响，以及土壤微生物多样性枯竭对 SDZ 降解的影响，使用“灭绝稀释法”和 C-SDZ。粪肥的施用影响了土壤的一些特性，如 pH 值、有机碳（OC）和大量营养物质，以及细菌群落结构和多样性。即使是微小的细菌多样性枯竭也会影响 SDZ 的矿化和不可提取残留（NER）形成率，但 NER 在 42 天内恢复，可能是由于土壤多样性的恢复。然而，这段时间可能足以将耐药基因传播到环境中。令人惊讶的是，未施肥的自然土壤（NS-S1）显示出更快的 SDZ 降解率（DT=2.0 与 21 天），并且有大量参与主要 SDZ 降解途径（矿化和主要 NER）的细菌家族，如 Isosphaeraceae、Ktedonobacteraceae、 Acidobacteriaceae_（Subgroup_1）、Micromonosporaceae 和 Sphingobacteriaceae。这一结果是独特的，与我们的假设相反，即长期施肥的土壤会表现出适应性优势，从而具有更高的 SDZ 降解率。文献表明，在酸性土壤中，磺胺嘧啶的瞬时化学降解导致 NER 的快速形成。我们的结果表明，如果发生化学降解，很快就会被微生物代谢（生物降解）所取代，由一群细菌进行，新形成的代谢物应该有利于 NER 的形成，因为 SDZ 的吸附性较低。这也表明 SDZ 的矿化是一种低冗余功能。
