Blair B G, Anderson K L
Department of Biological Sciences, Mississippi State University 39762, USA.
Can J Microbiol. 1999 Mar;45(3):242-9. doi: 10.1139/w99-004.
Scanning electron microscopy was used to detect ultrastructural protuberances on the cellulolytic anaerobe Clostridium cellulovorans. Numerous ultrastructural protuberances were observed on cellulose-grown cells, but few were detected on glucose-, fructose-, cellobiose-, or carboxymethylcellulose (CMC)-grown cells. Formation of these protuberances was detected within 2 h of incubation in cellulose medium, but 4 h incubation was required before numerous structures were observed on the cells. When a soluble carbohydrate or CMC was mixed with cellulose-grown cells, the ultrastructural protuberances could no longer be detected. In fact, no protuberances were observed within 5 min following the addition of glucose, cellobiose, or methylglucose to cellulose-grown cells. The presence of these protuberances corresponded with the binding of the Bandeiraea simplicifolia BSI-B4 isolectin to the cell. Cellulose-grown cells had a greater level of observable lectin binding than cellobiose-grown cells, and lectin binding was not detected on glucose- or fructose-grown cells. In addition, lectin binding ability was lost by cellulose-grown cells following the addition of glucose, fructose, or methylglucose to the cellulose medium. A cellulose-affinity protein fraction expressing cellulase activity was also detected in cell extracts of cellobiose- or cellulose-grown cultures. However, this protein fraction was not detected in extracts of glucose-grown cultures, and was rapidly lost (within 5 min) following the addition of glucose to cellulose-grown cultures. The ability of C. cellulovorans to adhere to cellulose was also affected by the energy substrate, but not in the same manner as the protuberance formation or the cellulase-containing protein fraction. Rather, cellobiose-, cellulose-, and CMC-grown cultures adhered to cellulose, but this adherence was not affected by addition of glucose to the medium. This is the first report that soluble carbohydrates caused the rapid loss of some cellulose-inducible systems of C. cellulovorans.
利用扫描电子显微镜检测纤维素分解厌氧菌食纤维梭菌（Clostridium cellulovorans）上的超微结构突起。在以纤维素生长的细胞上观察到大量超微结构突起，但在以葡萄糖、果糖、纤维二糖或羧甲基纤维素（CMC）生长的细胞上仅检测到少数突起。在纤维素培养基中孵育2小时内可检测到这些突起的形成，但在细胞上观察到大量结构之前需要孵育4小时。当将可溶性碳水化合物或CMC与以纤维素生长的细胞混合时，不再能检测到超微结构突起。事实上，向以纤维素生长的细胞中添加葡萄糖、纤维二糖或甲基葡萄糖后5分钟内未观察到突起。这些突起的存在与简单豆科凝集素BSI - B4同工凝集素与细胞的结合相对应。以纤维素生长的细胞比以纤维二糖生长的细胞具有更高水平的可观察到的凝集素结合，并且在以葡萄糖或果糖生长的细胞上未检测到凝集素结合。此外，向纤维素培养基中添加葡萄糖、果糖或甲基葡萄糖后，以纤维素生长的细胞失去了凝集素结合能力。在以纤维二糖或纤维素生长的培养物的细胞提取物中也检测到一种表达纤维素酶活性的纤维素亲和蛋白组分。然而，在以葡萄糖生长的培养物的提取物中未检测到该蛋白组分，并且向以纤维素生长的培养物中添加葡萄糖后该组分迅速消失（5分钟内）。食纤维梭菌附着于纤维素的能力也受能量底物影响，但方式与突起形成或含纤维素酶的蛋白组分不同。相反，以纤维二糖、纤维素和CMC生长的培养物附着于纤维素，但向培养基中添加葡萄糖不会影响这种附着。这是关于可溶性碳水化合物导致食纤维梭菌一些纤维素诱导系统迅速丧失的首次报道。
