U S Geological Survey, Great Lakes Science Center, Lake Michigan Ecological Research Station, Porter, Indiana 46304, USA.
Microbes Environ. 2012;27(2):164-70. doi: 10.1264/jsme2.me11305.
High densities of Escherichia coli and enterococci are common in freshwaters on Oahu and other Hawaiian Islands. Soil along stream banks has long been suspected as the likely source of these bacteria; however, the extent of their occurrence and distribution in a wide range of soils remained unknown until the current investigation. Soil samples representing the seven major soil associations were collected on the island of Oahu and analyzed for fecal coliforms, E. coli, and enterococci by the most probable number method. Fecal coliforms, E. coli, and enterococci were found in most of the samples analyzed; log mean densities (MPN ± SE g soil⁻¹) were 1.96 ± 0.18, n=61; 1.21 ± 0.17, n=57; and 2.99 ± 0.12, n=62, respectively. Representative, presumptive cultures of E. coli and enterococci collected from the various soils were identified and further speciated using the API scheme; at least six species of Enterococcus, including Enterococcus faecalis and Enterococcus faecium, were identified. In mesocosm studies, E. coli and enterococci increased by 100-fold in 4 days, after mixing sewage-spiked soil (one part) with autoclaved soil (nine parts). E. coli remained metabolically active in the soil and readily responded to nutrients, as evidenced by increased dehydrogenase activity. Collectively, these findings indicate that populations of E. coli and enterococci are part of the natural soil microflora, potentially influencing the quality of nearby water bodies.
大肠埃希氏菌和肠球菌在瓦胡岛和其他夏威夷岛屿的淡水中的密度很高。长期以来，人们一直怀疑溪流两岸的土壤是这些细菌的可能来源；然而，直到目前的调查，这些细菌在广泛的土壤中出现和分布的程度仍不清楚。在瓦胡岛上收集了代表七个主要土壤群的土壤样本，并采用最可能数法对粪便大肠菌群、大肠埃希氏菌和肠球菌进行了分析。在分析的大多数样本中都发现了粪便大肠菌群、大肠埃希氏菌和肠球菌；对数平均值（MPN±SE g 土壤⁻¹）分别为 1.96±0.18，n=61；1.21±0.17，n=57；2.99±0.12，n=62。从各种土壤中采集的大肠埃希氏菌和肠球菌的代表性推定培养物，使用 API 方案进行鉴定和进一步分类；鉴定出至少六种肠球菌，包括粪肠球菌和屎肠球菌。在中观模拟研究中，将污水污染的土壤（一份）与高压灭菌土壤（九份）混合后，大肠埃希氏菌和肠球菌在 4 天内增加了 100 倍。大肠埃希氏菌在土壤中仍保持代谢活性，并对营养物质有反应，这表现为脱氢酶活性增加。总的来说，这些发现表明大肠埃希氏菌和肠球菌种群是自然土壤微生物区系的一部分，可能会影响附近水体的质量。
