Texier Stéphanie, Prigent-Combaret Claire, Gourdon Marie Hélène, Poirier Marie Andrée, Faivre Pierre, Dorioz Jean Marcel, Poulenard Jérome, Jocteur-Monrozier Lucile, Moënne-Loccoz Yvan, Trevisan Dominique
UMR42 CARRTEL, INRA F74203, Thonon-les-Bains, France; Université de Savoie, F73376 Le Bourget du Lac, France.
J Environ Qual. 2008 Oct 23;37(6):2299-310. doi: 10.2134/jeq2008.0028. Print 2008 Nov-Dec.
Our knowledge of Escherichia coli (E. coli) ecology in the field is very limited in the case of dairy alpine grassland soils. Here, our objective was to monitor field survival of E. coli in cow pats and underlying soils in four different alpine pasture units, and to determine whether the soil could constitute an environmental reservoir. E. coli was enumerated by MPN using a selective medium. E. coli survived well in cow pats (10(7) to 10(8) cells g(-1) dry pat), but cow pats disappeared within about 2 mo. In each pasture unit, constant levels of E. coli (10(3) to 10(4) cells g(-1) dry soil) were recovered from all topsoil (0-5 cm) samples regardless of the sampling date, that is, under the snow cover, immediately after snow melting, or during the pasture season (during and after the decomposition of pats). In deeper soil layers below the root zone (5-25 cm), E. coli persistence varied according to soil type, with higher numbers recovered in poorly-drained soils (10(3) to 10(4) cells g(-1) dry soil) than in well-drained soils (< 10(2) cells g(-1) dry soil). A preliminary analysis of 38 partial uidA sequences of E. coli from pat and soils highlighted a cluster containing sequences only found in this work. Overall, this study raises the possibility that fecal E. coli could have formed a naturalized (sub)population, which is now part of the indigenous soil community of alpine pasture grasslands, the soil thus representing an environmental reservoir of E. coli.
在高山草原土壤中，我们对大肠杆菌在自然环境中的生态学认识非常有限。在此，我们的目标是监测大肠杆菌在四个不同高山牧场单元的牛粪及下层土壤中的野外存活情况，并确定土壤是否可构成一个环境储存库。采用选择性培养基通过最大可能数法对大肠杆菌进行计数。大肠杆菌在牛粪中存活良好（每克干牛粪中有10⁷至10⁸个细胞），但牛粪在约两个月内消失。在每个牧场单元中，无论采样日期如何，即雪覆盖下、雪融化后立即采样或在放牧季节（牛粪分解期间及之后），从所有表土（0 - 5厘米）样本中均能检测到恒定水平的大肠杆菌（每克干土中有10³至10⁴个细胞）。在根区以下的较深土壤层（5 - 25厘米）中，大肠杆菌的持久性因土壤类型而异，排水不良的土壤中回收的数量较多（每克干土中有10³至10⁴个细胞），而排水良好的土壤中数量较少（每克干土中<10²个细胞）。对来自牛粪和土壤的38个大肠杆菌部分uidA序列进行的初步分析突出显示了一个仅在本研究中发现的序列簇。总体而言，本研究提出了粪便大肠杆菌可能已形成归化（亚）种群的可能性，该种群现在是高山牧场草原原生土壤群落的一部分，因此土壤代表了大肠杆菌的一个环境储存库。
