Department of Soil, Water, and Climate, University of Minnesota, 1991 Upper Buford Circle, St. Paul, MN 55108, USA.
Microbes Environ. 2010;25(1):8-14. doi: 10.1264/jsme2.me09172.
While Escherichia coli is widely used as an indicator of fecal contamination of waterways, recent studies suggest that this bacterium may become "naturalized" to soils. In this study, we investigated the survival and growth of naturalized E. coli in temperate soil in northern Minnesota. A spontaneously-occurring, antibiotic resistant E. coli strain, KS7-NR, was added to a field site at 10(3) cells (g soil)(-1). The survival and growth of E. coli KS7-NR were followed from June to October, by using colony counts on agar plates supplemented with antibiotics, and by using quantitative PCR (qPCR) with strain-specific primers developed based on suppressive subtractive hybridization. Both plate count and qPCR analyses indicated that E. coli KS7-NR survived for more than 2 months in the field soil. Laboratory experiments showed that soil temperature, moisture, nutrients, and the presence of other soil organisms influenced growth and survival of E. coli KS7-NR in soil. Moreover, our results indicated that summer drought conditions that occurred during the field study likely limited in situ growth of E. coli at the field site. Taken together, these results suggest that E. coli strains can survive long-term and grow in soils, provided that abiotic factors are within their tolerance limits.
虽然大肠杆菌被广泛用作水环境污染的粪便污染指示物，但最近的研究表明，这种细菌可能会在土壤中“自然化”。在这项研究中，我们调查了自然化大肠杆菌在明尼苏达州北部温带土壤中的生存和生长情况。一种自发出现的、抗抗生素的大肠杆菌菌株 KS7-NR，以 10(3)细胞（g 土壤）（-1）的浓度添加到一个野外地点。通过使用琼脂平板上的菌落计数来补充抗生素，并使用基于抑制性差减杂交开发的针对特定菌株的定量 PCR(qPCR)，从 6 月到 10 月跟踪大肠杆菌 KS7-NR 的存活和生长情况。平板计数和 qPCR 分析均表明，大肠杆菌 KS7-NR 在野外土壤中存活了 2 个多月。实验室实验表明，土壤温度、湿度、养分和其他土壤生物的存在影响了大肠杆菌 KS7-NR 在土壤中的生长和存活。此外，我们的结果表明，在野外研究期间发生的夏季干旱条件可能限制了现场大肠杆菌的原位生长。综上所述，这些结果表明，只要非生物因素在其耐受范围内，大肠杆菌菌株就可以在土壤中长期生存和生长。
