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Fractal Growth and Morphological Change by a Cell Population

细胞群的分形生长和形态变化

基本信息

批准号：
04452053
负责人：
MATSUSHITA Mitsugu
金额：
$ 3.01万
依托单位：
CHUO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Bacterial colonies grow when a small amount of the cells are inoculated on the surface of nutrient-rich agar plates (substrates) and incubated appropriately. We have found that colony patterns change drastically when concentrations of nutrient and agar (controlling substrate softness) are varied. We have thus been able to establish quantitatively the morphological phase diagram of colony patterns by using Bacillus subtilis. Namely, we observed characteristic patterns such as self-similar DLA, compact but interfacially rough (self-affine) Eden-like, concentric-ring, densely branched DBM-like, and isotropic and homogeneous disk patterns. We also observed that individual bacterial cells start to able to move actively inside colonies when agar plates become softer. This active cell movement seems to trigger some morphological changes. Many rod-like bacterial species including Escherichia coli and Bacillus subtilis have been found to exhibit self-similar, DLA patterns due to the diffusion-limited condition of nutrient, when nutrient is poor and agar plates are rather hard. We can, therefore, conclude that the DLA mechanism is fairly universal for colony growth under these environmental conditions. For the isotropic and homogeneous disk colonies which are the simplest patterns we have ever observed we quantitatively measured the interfacial growth speed, population density and diffusion coefficient of individual cells inside colonies in detail. We thus elucidated that the growth of these colonies can be described by the Fisher's equation. However, we have not yet confirmed the self-affinity of Eden-like colonies, nor elucidated the growth mechanisms for other colony patterns.

少量细胞接种于营养丰富的琼脂板（底物）表面并适当孵育，菌落生长。我们发现，当营养物和琼脂（控制基质柔软度）的浓度变化时，菌落模式会发生急剧变化。因此，我们可以利用枯草芽孢杆菌定量地建立菌落形态相图。也就是说，我们观察到自相似的DLA，紧凑但界面粗糙（自仿射）的伊甸园样，同心环，密集分支的dbm样，以及各向同性和均匀的磁盘模式。我们还观察到，当琼脂板变软时，单个细菌细胞开始能够在菌落内活跃地移动。这种活跃的细胞运动似乎引发了一些形态变化。许多杆状细菌，包括大肠杆菌和枯草芽孢杆菌，由于营养物质的扩散受限，当营养物质较差，琼脂板较硬时，都表现出自相似的DLA模式。因此，我们可以得出结论，在这些环境条件下，DLA机制对于菌落生长是相当普遍的。对于我们观察到的最简单的各向同性和均匀的圆盘菌落，我们详细地定量测量了菌落内单个细胞的界面生长速度、种群密度和扩散系数。因此，我们阐明了这些菌落的生长可以用费雪方程来描述。然而，我们尚未证实伊甸园样菌落的自亲和性，也未阐明其他菌落模式的生长机制。