中国黄土剖面趋磁细菌的组成特征与生态意义

Compositional Features of Magnetotactic Bacteria in Loess of China and Their Ecological Significance

选择中国的黄土 -古土壤序列的趋磁细菌作为研究对象,以透射电镜、扫描电镜、生化实验和有机地球化学方法先后研究了从黄土地区陕西段家坡、甘肃西峰以及陕西洛川富集的趋磁细菌,结果表明,虽然趋磁细菌在黄土和古土壤层的形态有所差异,但它们均由细胞膜、细胞质和沿长轴排列的磁小体与气泡组成,在适宜的条件下它能生长出较多的磁小体。磁小体由氧化铁组成,并可从体内排出,使环境中部分Fe2 + 转变为Fe3 + ,促使地层磁化率增高,尤其在古土壤层段。中国黄土剖面中趋磁细菌的产量是地表温度、湿度、pH、铁含量的函数。与湖沼中的趋磁菌相比,它在菌体形态、磁小体的数量与排列方式上有很大差异,因而中国西北黄土地区的趋磁细菌是典型的生态物种。

The authors chose magnetotactic bacteria of the loess-paleosol sequences of China as a target and made successive studies on magnetotactic bacteria in layers of Duanjiapo section, layers of Xifeng section as well as S 5-1 layer in Luochuan section by such means as TEM, SEM, biochemical experiments, and organic geochemistry. The results show that they consist of membrane and cytoplasm as well as magnetosomes and gas balls arranged along long axes. Under the suitable conditions, a lot of magnetosomes grow in the magnetotactic bacteria. Magnetosomes consist of Fe 2O 3·H 2O, and can be discharged from the bacterial bodies to surrounding environment. This can change Fe 2+ to Fe 3+ and increase magnetic susceptibility in the layers, especially in the paleosol layers. The product of magnetotactic bacteria in the loess section of China is a function of temperature, humidity, pH value and content of iron at the surface. They are obviously different from magnetotactic bacteria in the lake and swamp in shape, quantity and arrangement of magnetosomes, and hence the magnetotactic bacteria in loessial region of Northwest China constitute a typical ecological species.