寡营养条件下超微细菌对邻苯二甲酸酯的生物降解

Biodegradation of phthalate esters by the ultramicro-bacterial consortium under the oligotrophic condition

从松花江干流下游的底泥中分离并筛选出能够在寡营养条件下降解邻苯二甲酸酯(PAEs)的超微细菌菌群,研究了该菌群对4种PAE——邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二乙酯(DEH)、邻苯二甲酸(2-乙基己)酯(DEHP)的降解能力。结果表明,4种PAE均可作为菌群的唯一碳源,菌群对4种PAE有不同的比生长速率和最大降解速率,比生长速率从大到小为DMP(0.176h^(-1))、DBP(0.158 5 h^(-1))、DEP(0.140 9 h^(-1))、DEHP(0.107 6 h^(-1)),最大降解速率从大到小为DEP(0.098 mg/(L·h))、DBP(0.062 7 mg/(L·h))、DMP(0.061 mg/(L·h))、DEHP(0.051 5 mg/(L·h))。利用极度稀释法从该菌群中分离出1株典型寡营养超微细菌菌株,命名为PAE-UM,根据16S rDNA序列系统发育分析,鉴定为丛毛单胞菌属(Curvibacter sp.)。

The present study is aimed to introduce our method for isolating an ultramicrobacterial consortium that is capable to degrade phthalate esters（PAEs）,which can be used mainly as plasticizers as one of the prior environmental pollutants in some countries,under oligotrophic conditions.For our isolation purpose,we have collected and chosen the ultramicrobacterial consortium from the sediment samples in the lower reach of Songhua River,one of the main riverbranches of Heilong River.The bacterial consortium we have collected and isolated has been found to be capable to degrade phthalic acid esters under the oligotrophic conditions.We have also found that the bacteria-consortium belongs to a kind of typical ultramicrobacterium,which can pass through the filters with their pore size of 0.45μm.What is more,we have also found that it also belongs to a kind of oligotrophic consortium that can not be cultivated by using or from the traditional highly nutrition media.Further studies let us discover that the aforementioned consortium is in a position to degrade four different kinds of phthalate esters（DMP,DBP,DEP,DEHP） under the oligotrophic condition with the pasteurized and filtered Evian water used as the growth medium.On the other hand,since the said consortium cannot be cultivated with the conventional plating methods,it is necessary to use the flow cytometry in combination with the fluorescence staining with SYBR Green I to analyze the bacterial concentration in the degradation process.In addition,it is also necessary to use high performance liquid chromatography to monitor the concentration changes of the phthalate esters.The results of our investigation have shown that the consortium under question is in a position to use all the four kinds of phthalate esters to function as the sole carbon and energy source under the oligotrophic condition.What is more,the consortium can also be used to degrade four kinds of PAEs at different maximal degradation rates in a descending order of specific growth rate in the given use,that is：DMP（0.176 h^（-1））DBP（0.158 5h^（-1）） DEP（0.140 9 h^（-1））DEHP（0.107 6 h^（-1））.The order of the maximum degradation rate can also be illustrated in a descending order;that is：DEP（0.098 mg/（L·））DBP（0.062 7mg/（L·h））DMP（0.061 mg/（L·h））DEHP（0.051 5mg/（L·h））.Therefore,it can be concluded that the isolated ultramicrobacterial consortium enjoys a capability to degrade various kinds of PAEs in different efficiencies.In addition,it has been proven that it is possible to purify one ultramicrobacterial strain,namely,PAE-UM,from the consortium with the extinction-dilution method,which is known as Curvibacter sp.based on the 16 S rDNA sequencing results.