Centro Interamericano de Recursos del Agua, Universidad Autonoma del Estado de Mexico, Toluca, Mexico.
Microb Ecol. 2012 Jul;64(1):140-51. doi: 10.1007/s00248-012-0010-5.
Persistence or degradation of synthetic antibiotics in soil is crucial in assessing their environmental risks. Microbial catabolic activity in a sandy loamy soil with pig manure using 12C- and 14C-labelled sulfamethazine (SMZ) respirometry showed that SMZ was not readily degradable. But after 100 days, degradation in sulfadiazine-exposed manure was 9.2%, far greater than soil and organic manure (0.5% and 0.11%, respectively, p < 0.05). Abiotic degradation was not detected suggesting microbial catabolism as main degradation mechanism. Terminal restriction fragment length polymorphism showed biodiversity increases within 1 day of SMZ spiking and especially after 200 days, although some species plummeted. A clone library from the treatment with highest degradation showed that most bacteria belonged to α, β and γ classes of Proteobacteria, Firmicutes, Bacteroidetes and Acidobacteria. Proteobacteria (α, β and γ), Firmicutes and Bacteroidetes which were the most abundant classes on day 1 also decreased most following prolonged exposure. From the matrix showing the highest degradation rate, 17 SMZ-resistant isolates biodegraded low levels of 14C-labelled SMZ when each species was incubated separately (0.2-1.5%) but biodegradation was enhanced when the four isolates with the highest biodegradation were incubated in a consortium (Bacillus licheniformis, Pseudomonas putida, Alcaligenes sp. and Aquamicrobium defluvium as per 16S rRNA gene sequencing), removing up to 7.8% of SMZ after 20 days. One of these species (B. licheniformis) was a known livestock and occasional human pathogen. Despite an environmental role of these species in sulfonamide bioremediation, the possibility of horizontal transfer of pathogenicity and resistance genes should caution against an indiscriminate use of these species as sulfonamide degraders.
土壤中合成抗生素的持久性或降解性对评估其环境风险至关重要。使用 12C 和 14C 标记的磺胺甲恶唑 (SMZ) 呼吸测定法，在含有猪粪的砂壤土中研究微生物的代谢活性表明，SMZ不易降解。但是，在磺胺嘧啶暴露的粪便中，100 天后的降解率为 9.2%，远高于土壤和有机肥料（分别为 0.5%和 0.11%，p<0.05）。未检测到非生物降解，表明微生物代谢是主要的降解机制。末端限制性片段长度多态性显示，SMZ 加标后 1 天内生物多样性增加，尤其是 200 天后，尽管有些物种急剧下降。降解率最高的处理的克隆文库显示，大多数细菌属于α、β和γ类变形菌、厚壁菌门、拟杆菌门和酸杆菌门。在长时间暴露后，最初最丰富的α、β和γ类变形菌、厚壁菌门和拟杆菌门也减少最多。在显示最高降解率的基质中，当单独培养时，17 种磺胺类药物抗性分离株可生物降解低水平的 14C 标记磺胺甲恶唑（0.2-1.5%），但当以最高生物降解能力的四种分离株在共培养物中培养时（根据 16S rRNA 基因测序，芽孢杆菌、假单胞菌、产碱杆菌和脱卤微菌），磺胺甲恶唑的生物降解率提高，20 天后可去除高达 7.8%的磺胺甲恶唑。这些物种中的一种（地衣芽孢杆菌）是一种已知的家畜和偶发性人类病原体。尽管这些物种在磺胺类药物生物修复中具有环境作用，但应警惕致病性和耐药性基因的水平转移，避免将这些物种作为磺胺类药物降解剂不加区别地使用。
