Merroun M L, Ben Chekroun K, Arias J M, González-Muñoz M T
Departamento de Microbiologi;a, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, 18071, Granada, Spain.
Chemosphere. 2003 Jul;52(1):113-20. doi: 10.1016/S0045-6535(03)00220-0.
Myxococcus xanthus is a soil bacterium of the myxobacteria group and is abundant in almost all soils. Its role in soil ecology is considered significant. One noteworthy characteristic of the bacterium is that it produces large quantities of extracellular polymeric substances (EPS). It is also known that its biomass has the capacity to fix heavy metals. Here it is reported that M. xanthus was able to accumulate 0.6 mmol of La per g of wet biomass and/or 0.99 mmol per g of dry biomass. Transmission Electron Microscopy (TEM) observation of M. xanthus cells treated with La showed that a substantial amount of this cation was fixed in the EPS and in the cell wall. Smaller amounts were also observed in the cytoplasm. Fixed La appeared as phosphate in all cellular locations. The results given here also show that the use of La enables TEM observation of the M. xanthus EPS as a dense fibrillar net surrounding the cells. This technique is relatively easy and prevents EPS collapse, which occurs frequently during the fixation and dehydration procedures commonly used in preparations for TEM observations. Since antibodies are no longer required, the La stain can be carried out without delaying bacterial cell cultivation or isolation. In addition, the presence of La in cell cytoplasm without cell degeneration suggests that this microorganism could be used as a model in the study of bacteria-lanthanide interactions.
黄色粘球菌是粘细菌群中的一种土壤细菌，在几乎所有土壤中都很丰富。其在土壤生态中的作用被认为很重要。这种细菌的一个显著特征是它能产生大量胞外聚合物（EPS）。还已知其生物质具有固定重金属的能力。据报道，黄色粘球菌每克湿生物质能够积累0.6毫摩尔镧和/或每克干生物质积累0.99毫摩尔镧。对用镧处理的黄色粘球菌细胞进行透射电子显微镜（TEM）观察表明，大量这种阳离子固定在EPS和细胞壁中。在细胞质中也观察到较少量。固定态镧在所有细胞位置均以磷酸盐形式出现。这里给出的结果还表明，使用镧能够通过TEM观察到黄色粘球菌的EPS呈围绕细胞的致密纤维网。该技术相对简单，可防止EPS塌陷，而EPS塌陷在TEM观察样品制备中常用的固定和脱水过程中经常发生。由于不再需要抗体，进行镧染色不会延迟细菌细胞培养或分离。此外，细胞质中存在镧而细胞未退化表明这种微生物可作为研究细菌 - 镧系元素相互作用的模型。
