趋磁细菌研究方法及模式菌AMB-1生理特性研究

【作者】 李金华；

【导师】 陈冠军；

【作者基本信息】 山东大学 ， 微生物学， 2006， 硕士

【摘要】 趋磁细菌是一类能在细胞内积累生物膜包被的，纳米尺寸、单磁畴级别晶体颗粒（磁小体）的细菌。磁小体在细胞内呈链状或丛状排列，作为细菌的“生物磁针（biocompass）”，感受地球磁场或外加磁场，使菌体沿磁场方向定向游弋或排列，这种特性也叫“趋磁性”。由于趋磁细菌独特的磁场运动特性、生物学特性以及磁小体作为生物活性物质的固定载体、磁记忆材料等方面广阔的应用前景，趋磁细菌和磁小体的研究引起了微生物学、生物磁学、地质学和材料学领域学者的兴趣。30年来，研究者在诸如趋磁细菌的生态分布、菌种分离筛选、系统进化和分类以及菌体生理生化特征，磁小体的物化特性、合成机制和生物矿化过程等方面，对趋磁细菌展开了深入系统的研究，同时，磁小体在磁性纳米材料、生物医药工程等领域的应用也得到了广泛的研究。 磁螺菌AMB-1 （Magnetospirillum sp．AMB-1） 是Mataunaga等从日本东京一天然淡水泉沉积物（pH6.5-7.0）中分离得到的一株螺旋形趋磁细菌。与其它纯培养的趋磁细菌相比，AMB-1氧耐受度高，微好氧和厌氧条件下合成Fe₃O₄型磁小体，该菌可以在琼脂固体平板上生长，形成不含磁小体的白色菌落或含磁小体的棕黑色菌落。因此，AMB-1是研究趋磁细菌非常合适的模式菌株，该菌的全基因组测序也完成。但目前人们对磁小体生物矿化的精细过程仍不清楚，磁小体发酵生产的产量仍然很低，制约了磁小体的研究应用。 由于缺乏必要的趋磁细菌测量系统和趋磁细菌的研究方法，以及菌株分离培养难度极大，国内的趋磁细菌研究进展比较缓慢。本论文以磁螺菌AMB-1（Magnetospirillum sp．strain AMB-1，ATCC 700264）为模式菌株，对趋磁细菌的物理表征及其生理特征等方面开展了细致的研究，有许多新发现，对趋磁细菌的物理与生理特征有了新的认识。本项研究取得如下研究结果： ① 建立了趋磁细菌的磁场运动性观察和趋磁细菌磁分离方法 利用条形磁铁形成的简单磁场，建立了利用标准液滴法进行趋磁细菌磁场方向定向运动性观测方法，发现含有磁小体的AMB-1细胞沿磁场方向分层相向快更多还原

【Abstract】 Magnetotactic bacteria (also called Magnetic bacteria) are widespread aquatic microorganisms that use unique intracellular organelles to navigate along the Earth’s magnetic field, and such navigation is known as magnetotaxis. These organelles, called magnetosomes, consist of membrane-enclosed magnetite crystals that are thought to help to direct bacterial swimming towards growth-favouring microoxic zones at the bottom of natural waters. Overall, magnetotsome crystals have narrow size ranges (single magnetic domain size range), species-specific crystal morphologies and exhibit specific arrangements within the cell. During the past 30 years, researchers from several laboratories have made significant progress in elucidating the ecology, screening, phylogenesis, physiology and biotechnological applications of magnetic bacteria. Also, the molecular biological, biochemical, chemical and genetic mechanisms of magnetosome formation have been explored intensively.Magnetospirillum sp. AMB-1 was first isolated from freshwater sediment collected from a natural spring at Kognei (Tokyo) by Matsunaga et al. It can grow under both aerobic and microaerobic conditions, forming white or black-brown colonies on or in agar plates. AMB-1 cells grown under microaerobic conditions are able to synthesize magnetosomes, with an average diameter of 50nm, arranged in a chain. Although researchers from several laboratories have made a great deal of progress in several aspects such as genome sequencing, the process of magnetosome biomineralization and its biotechnological applications, details of the process of magnetosome synthesis are far from well elucidated. On the other hand, the yield of magnetosomes is still too low to be applied on a large scale. Because of the lack of necessary Bacteriodrome and appropriate research methods, magnet-sensitive bacteria and microorganisms containing electron opaque particles were sometime mistaken for magnetic bactria, which also hinders the research development in this field.With Magnetospirillum sp. AMB-1 at hand, we have carried out experiments from several aspects and results achieved are as follows:更多还原