Wiebe M G, Robson G D, Cunliffe B, Oliver S G, Trinci A P
Department of Cell and Structural Biology, School of Biological Sciences, University of Manchester, UK.
J Gen Microbiol. 1993 Nov;139(11):2811-7. doi: 10.1099/00221287-139-11-2811.
By monitoring increases and decreases in the proportion of cycloheximide-resistant macroconidia, periodic selection was observed in populations of the filamentous fungus Fusarium graminearum, grown in glucose-limited chemostat cultures. The results indicated that periodic selection of advantageous mutants of F. graminearum occurred at intervals of about 124 h at both high (D = 0.19 h-1, approximately 34 generations) and low (D = 0.06 h-1, approximately 11 generations) dilution rates. Several 'adaptive' peaks (each indicating the appearance of an advantageous mutation) were observed before morphological (highly branched) mutants appeared in the populations; these mutants have previously been observed to have a selective advantage over the parental strain. At intervals, macroconidia harvested from the chemostat were used to inoculate plates of non-antibiotic-containing agar medium, and it was possible to monitor periodic selection in the original chemostat culture using second generation macroconidia harvested from these cultures. The proportion of cycloheximide-, potassium chlorate-, and p-fluoro-DL-phenylalanine-resistant macroconidia in these second generation macroconidia changed in a pattern similar to that observed when monitoring the proportion of cycloheximide-resistant macroconidia in the first generation population harvested directly from the chemostat. The experiments demonstrated that populations of filamentous fungi are heterogeneous and that much of this heterogeneity may already be present at the end of batch growth, i.e., before the onset of continuous cultivation.
通过监测抗环己酰亚胺大分生孢子比例的增减，在葡萄糖受限的恒化器培养中生长的丝状真菌禾谷镰刀菌群体中观察到了周期性选择。结果表明，在高稀释率（D = 0.19 h-1，约34代）和低稀释率（D = 0.06 h-1，约11代）下，禾谷镰刀菌优势突变体的周期性选择每隔约124小时发生一次。在群体中出现形态学上（高度分支）的突变体之前，观察到了几个“适应性”峰值（每个峰值表明一个优势突变的出现）；这些突变体先前已被观察到相对于亲本菌株具有选择优势。每隔一段时间，从恒化器收获的大分生孢子被用于接种不含抗生素的琼脂培养基平板，并且可以使用从这些培养物中收获的第二代大分生孢子来监测原始恒化器培养中的周期性选择。这些第二代大分生孢子中抗环己酰亚胺、抗氯酸钾和抗对氟-DL-苯丙氨酸的大分生孢子比例的变化模式，与直接从恒化器收获的第一代群体中监测抗环己酰亚胺大分生孢子比例时观察到的模式相似。实验表明，丝状真菌群体是异质的，并且这种异质性的很大一部分可能在分批生长结束时，即在连续培养开始之前就已经存在。
