湛江湾抗生素抗性基因的时空分布及其影响因素

Spatiotemporal distribution and influencing factors of antibiotic resistance genes in Zhanjiang Bay

为探究湛江湾抗生素抗性基因(antibiotic resistance gene,ARGs)的时空分布特征及环境因子对其分布的潜在影响,采用实时荧光定量PCR(qPCR)技术,研究了湛江湾表层沉积物中磺胺类、四环素类和氟喹诺酮类ARGs(sul1、tetQ和qnrS),整合子基因(intI1),以及16S rRNA基因4个季节的丰度变化。结果表明:湛江湾表层沉积物中,ARGs各基因的平均绝对丰度均呈现冬季最高、夏季最低,而其平均相对丰度均呈现夏季最高,说明ARGs存在明显的季节性分布特征;从站位分布来看,3种ARGs的平均绝对丰度均呈现出Z21>Z04>Z06,而平均相对丰度均表现为Z06>Z21>Z04,说明ARGs的分布存在明显的空间分布特征;斯皮尔曼(Spearman)相关性分析显示,ARGs基因之间,以及ARGs、intI1分别与16S rRNA基因绝对丰度之间均呈显著正相关(P<0.05),intI1与sul1相对丰度之间呈显著正相关(P<0.05),ARGs的绝对和相对丰度分别与四环素类和氟喹诺酮类抗生素及Mn、Cu等重金属存在一定程度的相关性;基因与环境因子的RDA和VPA分析结果共同表明,重金属对ARGs的时空分布具有重要贡献。研究表明,湛江湾表层沉积物中ARGs的分布受到细菌总量、intI1、理化因子、抗生素及重金属的潜在影响,且环境因子中重金属的潜在影响最大,周围的城市、工业污水排放均是影响其季节和空间分布的潜在污染源。

In order to explore the spatial and temporal distribution characteristics of antibiotic resistance genes(ARGs) and the potential influence of environmental factors on their distribution in Zhanjiang Bay(109°40′-110°58′E,20°13′-21°57′N),the seasonal abundance changes in sulfonamides,tetracyclines and fluoroquinolones ARGs(sul1,tetQ and qnrS),class 1 integron(intI1) and 16S rRNA genes were seasonally surveyed in surface sediments of Zhanjiang Bay by real-time quantitative PCR.It was found that the maximal average absolute abundance of ARGs genes in surface sediments in Zhanjiang Bay was observed in winter and the minimal in summer,with the maximal average relative abundance in summer,indicating that the distribution of ARGs had obvious seasonal distribution characteristics.In terms of the station distribution,the descending order of average absolute abundance of the three types of ARGs was expressed as Z21Z04Z06,and the average relative abundance as Z06Z21Z04,indicating that there was obvious spatial distribution characteristics in the distribution of ARGs.The Spearman correlation analysis revealed that there was significantly positive correlation between the absolute abundance of the three ARGs,intI1 and 16S rRNA genes(P0.05),and that the relative abundance of intI1 was also shown to be significantly positively correlated with the relative abundance of sul1(P0.05).The correlation analysis between genes and environmental factors showed that the absolute and relative abundances of ARGs were related to tetracyclines and fluoroquinolone antibiotics,as well as heavy metals such as Mn and Cu.The results of redundancy analysis(RDA) and variation portioning analysis(VPA) of genes and environmental factors showed that heavy metals played an important role in the spatiotemporal distribution of ARGs.The distribution of ARGs in surface sediments in Zhanjiang Bay was potentially affected by the total amount of bacteria,intI1,physicochemical factors,antibiotics and heavy metals,with the maximal potential impact of heavy metals in environmental factors.The surrounding urban and industrial wastewater discharges are potential sources of pollution affecting its seasonal and spatial distribution.