Study on the modeling of colony pattern selection of filamentous fungi

丝状真菌在不同的环境条件下表现出不同的菌落生长模式。本研究构建了具有营养水平、营养扩散和菌丝生长速率三个主要参数的多层菌落。通过模型生长与实际菌落生长的比较，探讨菌落模式的选择规律。在没有养分扩散的情况下，模型菌落在任何营养水平下都表现出相当的自亲和性，可以维持菌落的生长。无限营养极限情况下也得到了相同的结果。然而，在多层模型中，锋面粗糙度的增长指数依赖于营养水平。这些结果表明，蜂群空间内部菌丝的产生影响了蜂群锋面的粗化。养分的扩散导致了生长模式的变化。在固定的养分水平和养分扩散系数下，随着生长速率的降低，菌落表现为反应限制生长，并形成密集的聚集格局。在此条件下，随着营养水平的降低，分支形态通过反应限制过程发展。将模型菌落形态与实际菌落形态进行比较，发现菌丝生长速率对环境养分水平的固有响应方式存在模式选择规律。将中性曲霉的野生菌株和突变菌株分为两类；在任何营养和琼脂水平下，它们都保持均匀生长，而在低营养水平下，它们表现出分枝模式。通过对不同营养水平下菌落扩张率的测量，这些形态类型可能与低营养水平下突变诱导的生长速率衰减有关。此外，为了考虑菌丝老化等对菌丝生长的抑制作用，我们开始对芽孢杆菌和其他菌株进行菌丝生长速率的长期测量。菌丝生长速率在生长过程中呈逐渐或急剧的衰减，表明菌丝生长速率下降的方式与环境养分水平有关。少

Filamentous fungi show variety of colony growth patterns depending upon the environmental conditions. In this study, a multi-layer mycelial colony that had three main parameters of nutrient level, nutrient diffusion and hyphal growth rate was constructed. By comparing the model growth with the real fungal colony growth, the selection rules of mycelial colony patterns were investigated.Without nutrient diffusion, the model colonies exhibited equivalent self-affinity in their roughening of colony fronts at any nutrient levels the colony growth can be maintained. The same result was also obtained for the cases of infinite nutrient limit case. However, the growth exponents of front roughness were found dependent upon the nutrient levels for the multi-layer models. These results showed that the hyphal production in the interior of the colonized space affected the roughening of colony fronts.The nutrient diffusion brought about the variation of growth patterns. Particularly, as the growth ra … More te was lowered at fixed nutrient levels and nutrient diffusion coefficient, the colony exhibited reaction-limited growth and formed densely aggregated patterns. Under this condition, as the nutrient level was lowered, the ramified morphology was found to develop through reaction-limited process.By comparing the model colony morphology with the real mycelial colonies, the pattern selection rule was found to exist in the inherent manner of response in the hyphal growth rate to the environmental nutrient levels. The wild and mutant strains of Aspergillus nidulans were grouped into two types; those maintained uniform growth at any nutrient and agar levels, and those exhibited ramified patterns at low nutrient levels. By measuring the colony expansion rates at various nutrient levels, these morphological types can be related with the mutation-induced decay of the growth rate at low nutrient levels.Further, to consider the effect of growth inhibition by the hyphal aging etc., long-term measurement of hyphal growth rate was commenced for A. nidulans and other strains. Gradual or steep decay of hyphal growth rate was found in the growth process, and it was suggested that the manner of growth rate reduction was dependent upon the environmental nutrient levels. Less