Role of Surface-Active Lipids in Fractal Morphogenesis.

沙雷氏菌产生的表面活性外脂具有促进分形菌落形态发生的活性。测定了这些新型脂质的结构。serrawetin (S. marcescens) W2是一种含有1个脂肪酸（3-羟基癸酸）和5个氨基酸的环沉积肽。该肽被认为是d -亮氨酸（n与脂肪酸的羧酸键合）- l -丝氨酸-l -苏氨酸- d -苯丙氨酸-l -异亮氨酸（3-羟基键合）。rubbiwettin (from S. rubidaea) R1被认为是3-（3'-羟基十四烷氧基）癸酸酯、3-（3'-羟基十六烷氧基）癸酸酯和少量分子异构体的混合物。rubbiwetin RG1的结构为β - d -葡萄糖吡喃基3-（3′-羟基十四烷氧基）癸酸酯。根据扩散限制聚集模型（DLA），细菌菌落的分形维数在1.7 ~ 1.8之间。在分形菌落生长中，还发现了屏蔽和排斥效应。因此，细菌菌落在二维营养浓度场中的生长通过扩散限制过程导致分形图案的形成。表面张力似乎对细菌在琼脂表面的易位有深远的影响。我们所描述的生物表面活性剂可以减轻在生长的菌落边缘工作的这种负担。通过引入表面张力参数的DLA模型的计算机仿真，证明了类似的模式形成。

Surface-active exolipids produced by Serratia spp. were shown to be active in promotion of fractal colony morphogenesis. Structures of these novel lipids were determined. Serrawettin (form S. marcescens) W2 was a cyclodepsipeptide containing a fatty acid (3-hydroxydecanoic acid) and five amino acids. The peptide was proposed to be D-leucine (N-bonded to the carboylate of the fatty acid)-L-serine-L-threonine-D-phenylalanine-L-isoleucine (bonded to the 3-hydroxyl group). Rubiwettin (from S. rubidaea) R1 was proposed to be a mixture of 3-(3'-hydroxytetradecanoyloxy) decanoate, 3-(3'-hydoxyhexadecenoyloxy) decanoate and minor molecular isomers. The structure of rubiwettin RG1 was proposed to be beta-D-glucopyranosyl 3-(3'-hydroxytetradecanoyloxy) decanoate. As suggested by the diffusion-limited aggregation model (DLA) theoretically, fractal dimensions of bacterial colonies were shown to be 1.7 - 1.8 by the box-counting method. In the fractal colony growth, shielding and repulsion effects were also recognized. Thus, bacterial colony growth in a two-dimensional nutrient concentration field was shown to results in fractal pattern formation through diffusion-limited processes. Surface tension seems to exert profound effect on bacterial translocation on the agar surface. Biosufactant described by us may lighten such burden working at the growing colony periphery. Similar pattern formations were demonstrated by computer simulation of DLA model introducing a surface tension parameter.