Role of Surface-Active Lipids in Fractal Morphogenesis.

沙雷氏菌属产生的表面活性外泌脂在促进分形菌落形态发生中表现出活性。这些新的脂质的结构进行了测定。Serrawettin（S型）marcescens）W_2是一种环缩肽，含有一个脂肪酸（3-羟基癸酸）和5个氨基酸。该肽被认为是D-亮氨酸（N-键合到脂肪酸的羧酸酯上）-L-丝氨酸-L-苏氨酸-D-苯丙氨酸-L-异亮氨酸（键合到3-羟基上）。Rubiwettin（来自S. rubidaea）R1可能是3-（3 '-羟基十四烷酰氧基）癸酸酯、3-（3'-羟基十六烯酰氧基）癸酸酯和少量分子异构体的混合物。Rubiwettin RG 1的结构被认为是β-D-吡喃葡萄糖基3-（3 '-羟基十四烷酰氧基）癸酸酯。根据扩散限制聚集模型（DLA）理论，用盒计数法计算了细菌菌落的分形维数为1.7 - 1.8。在分形菌落生长过程中，还发现了屏蔽和排斥效应。因此，细菌菌落生长在一个二维的营养浓度场被证明是通过扩散限制过程的分形图案形成的结果。表面张力对细菌在琼脂表面的迁移有重要影响。我们所描述的生物表面活性剂可以减轻在生长的菌落周边工作的这种负担。通过引入表面张力参数的DLA模型的计算机模拟，证明了类似图案的形成。

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.