—株G~-球形趋磁细菌的发现与表征

在玄武湖水域发现一株 Ｇ－ 球形趋磁细菌 Ｘ Ｗ － １ ，光学显微镜下观察，可见菌体在地磁场的作用下，快速北向游移，平均游动速率约为０ ．１４ ｍ ｍ／ｓ ，该菌株对磁场的作用极其敏感．透射电镜观察显示，在每一菌体的细胞壁上镶嵌了１２ 颗左右的磁小体，磁小体的大小和形状均匀一致，每颗磁小体长约６０ｎ ｍ ，宽４０ｎｍ ，ｘ 射线能谱测试分析表明，磁小体为铁的氧化物．

DISCOVERY AND CHARACTERIZATION OF A STRAIN OF MAGNETOTACTIC COCCUS

Iron containing bacteria from diverse aquatic environments which orient and swim in a preferred direction in a magnetic fields have been described. Cellullar iron is localized in crystals within these bacteria.The magnetic particles, iron rich, are called magnetosomes. The magnetosomes of most magnetotactic bacteria contain iron oxide particles, but some magnetotactic species contain iron sulfide partices instead. Here we report the discovery of magnetic iron oxide crystals in a strain of G magnetic coccus (XW 1) found in Xuanwu Lake at Nanjing. It was observed under an optical microscope that the coccus orientated and migrated along magneticfield lines and aggregated at the nothern extremity of the slide by responding to geomagnetism. The average velocity of the migration was 0.14 mms -1 . Transmission electron microscope (TEM) observation showed that each coccus contained about twelve iron rich magnetosomes with 60 nm in length and 40 nm in width and uniform in shape. In all magnetotactic microorganisms studied so far, those magnetosomes were enveloped by a mambrane and were localized intracellular or extracellular; however, magnetosomes in XW 1 were embedded in the wall of cells The dimensions of the magnetosomes in strain XW 1 are within the range of single domain, thus, the magnetite in these cells constitutes a biomagnetic compass. The results of energy dispersive X ray microanalysis showed that the magentosomes were iron oxide.