Study on the modeling of colony pattern selection of filamentous fungi

丝状真菌根据环境条件表现出不同的菌落生长模式。本研究构建了一个由营养水平、营养扩散和菌丝生长速率三个主要参数组成的多层菌丝菌落。通过与实际菌落生长的比较，研究了菌丝菌落模式的选择规律，在没有营养扩散的情况下，在任何营养水平下，模型菌落在菌落前沿的粗化过程中表现出相当的自亲和力，菌落的生长可以保持。对于无限营养极限的情况也得到了同样的结果。然而，在多层模式中，锋面粗糙度的增长指数依赖于营养水平。这些结果表明，定殖空间内部菌丝的产生影响了菌落锋面的粗化，营养物质的扩散导致了菌落生长方式的变化。尤其是随着…的增长在一定的营养水平和养分扩散系数下，菌落的TE降低较多，菌落呈反应限制生长，形成密集聚集格局。在此条件下，随着营养水平的降低，分枝形态的形成是反应受限的过程，通过将模型菌落形态与实际菌丝菌落进行比较，发现菌丝生长速率对环境营养水平的内在响应方式存在着模式选择规律。将野生菌株和突变菌株分为两类，一类是在任何营养和琼脂水平下都能保持均匀生长的菌株，另一类是在低营养水平下表现出分枝模式的菌株。通过测量不同营养水平下的菌落扩展速率，这些形态类型可能与低营养水平下突变诱导的生长速率的衰退有关。此外，为了考虑菌丝老化等对生长抑制的影响，开始对根瘤拟青霉等菌株的菌丝生长速率进行长期测量。在菌丝生长过程中，菌丝生长速率逐渐下降或急剧下降，表明菌丝生长速度下降的方式与环境营养水平有关。较少

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