粘粒矿物对细菌吸附的测定方法

A METHOD FOR DETERMINATION OF BACTERIA ADSORPTION BY CLAY MINERALS

本文目的是建立粘粒矿物对细菌吸附测定的方法。采用密度梯度分离介质-Nycodenz,通过测定蛋白质与菌量的相关性,探讨了分离液的分离悬浮效果,摸索了适宜菌量、矿物量,以及吸附时间等条件。结果表明:采用测定细菌细胞的蛋白质含量来表征矿物表面细菌的吸附量是可行的;浓度为60%(w/v)、密度1.31 g ml-1的Nycodenz密度梯度分离液可有效地分离矿物—细菌体系中被矿物吸附的细菌与游离的细菌;在此基础上,建立了粘土矿物表面吸附细菌的测定方法。

Interactions between bacteria and clay minerals are ubiquitous in soil and sediments. Previous studies on bioadsorption of bacteria focused mainly on large particles like quartz sands. Few methods for investigation of bacteria on clayey soil components are available. This study aims to establish a method for determination of adsorption of bacteria on clay minerals. Kaolinite and B. thuringiensis were used as the test bacterial strain and clay mineral. Nycodenz--density gradient solution was used to separate free bacterial cells from those adsorbed. Correlation between total protein and count of bacteria was analyzed. Suspending and separating effects of Nycodenz solution on bacteria and minerals were tested. Appropriate ranges of bacterial number and clay mineral, and equilibrium time were determined. Results show significant correlation between total bacterial protein and count of bacteria （R^2 = 0.991 9）. Total protein of bacteria could be used to represent the amount of bacteria adsorbed on minerals. Data reveal that Nycodenz solution, 60 % （w/v） in concentration and 1.31 g ml^-1 in density, is an efficient density gra- dient medium to separate free bacteria from those adsorbed on clay minerals. No interferences were observed of the 12 % （v/v） Nycodenz solution on protein measurement by the Bradford method. Maximum adsorption of bacteria on kaolinite occurred 60 min after getting in contact and then leveled off. The method could be extended to the study on interactions of minerals and microorganisms.