Robles S, Rodríguez J M, Granados I, Guerrero M C
Department of Ecology, Faculty of Sciences, Autonomous University of Madrid, Cantoblanco, Spain.
Int Microbiol. 2000 Sep;3(3):187-91.
We studied the vertical distribution of sulfite-reducing clostridia in the sediment of a Spanish high-mountain lagoon (Laguna Grande de Gredos, central Spain), with optimal sediment characteristics (temperature < 20 degrees C) to maintain spores without growing. This allowed us to assess the original numbers of sulfite-reducing clostridia endospores settled, without postdepositional growing. Sulfite-reducing clostridia are normal inhabitants of the intestinal microbiota of humans and other mammals. These microorganisms may form endospores, which allow the bacteria to survive in almost any habitat, either terrestrial or aquatic, waiting for favorable conditions for growth. Sulfite-reducing clostridia could be suitable indicators of past human pollution because they have a great longevity in natural habitats and they cannot multiply at temperatures below 20 degrees C or in the presence of O2. We found a great increase in the numbers of clostridia (expressed as colony-forming units per gram [CFU/g] of dry weight of sediment) since the 1970s, which reflects the rise of human pressure caused by the practice of outdoor activities. Clostridia CFU/g rose dramatically after the faulty operation of the depuration system of a mountain refuge built close to the lagoon. We compared the vertical distribution of clostridia CFU/g from Laguna Grande sediments with those from a neighbor lagoon (Laguna Cimera), which showed less tourist pressure and no direct disposal of sewage. Finally, we agree with the usefulness of the numbers of sulfite-reducing clostridia as indicators of past pollution.
我们研究了西班牙一座高山湖泊（西班牙中部格雷多斯大湖）沉积物中亚硫酸盐还原梭菌的垂直分布情况，该湖泊具有适宜的沉积物特征（温度<20摄氏度），能够维持孢子状态而不生长。这使我们能够评估沉降的亚硫酸盐还原梭菌内生孢子的原始数量，而不会出现沉积后生长的情况。亚硫酸盐还原梭菌是人类和其他哺乳动物肠道微生物群的正常居民。这些微生物可以形成内生孢子，使细菌能够在几乎任何陆地或水生栖息地中存活，等待有利的生长条件。亚硫酸盐还原梭菌可能是过去人类污染的合适指标，因为它们在自然栖息地中具有很长的寿命，并且在低于20摄氏度的温度下或有氧存在时无法繁殖。我们发现自20世纪70年代以来梭菌数量（以每克沉积物干重的菌落形成单位[CFU/g]表示）大幅增加，这反映了户外活动造成的人类压力上升。靠近湖泊建造的一个山间避难所的净化系统出现故障后，梭菌CFU/g急剧上升。我们将格雷多斯大湖沉积物中梭菌CFU/g的垂直分布与附近一个游客压力较小且没有直接污水排放的湖泊（西梅拉湖）的进行了比较。最后，我们认同亚硫酸盐还原梭菌数量作为过去污染指标的有用性。
