Vital Marius, Hammes Frederik, Egli Thomas
Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland.
Environ Microbiol. 2008 Sep;10(9):2387-96. doi: 10.1111/j.1462-2920.2008.01664.x. Epub 2008 May 28.
Whereas much information on the die-off of Escherichia coli in the aquatic environment is available, only few data support its growth under such conditions. We therefore investigated batch growth in microcosms containing different types of sterile freshwater. The water samples were inoculated with low starting cell concentrations of E. coli O157 (3 x 10(3) cells ml(-1)) and growth was followed using nucleic acid staining combined with flow cytometry. We demonstrated that E. coli O157 is able to grow in sterile freshwater at low carbon concentrations, which is against the common view that cell numbers decline over time when added to freshwater samples. A correlation between apparent assimilable organic carbon (AOC(app)) concentration and the final cell concentration reached by E. coli O157 was established (P < 0.01). A considerable fraction of the AOC(app) (34 +/- 13%) was used by E. coli O157 but the numerical cell yield was about five-times lower in comparison with the bacterial AOC-test community, which originated from natural freshwater. On average, the maximum specific growth rate (mu(max)) of E. coli O157 growing in sterile freshwater at 30 degrees C was 0.19 +/- 0.07 h(-1). Batch growth assays at five different temperatures revealed a positive influence of temperature on mu(max) of E. coli O157. The results give new information on the behaviour of this common pathogen in the aquatic environment and contribute to microbial risk assessment in order to prevent spreading of water-borne diseases.
虽然已有许多关于水生环境中大肠杆菌死亡的信息，但仅有少量数据支持其在这种条件下的生长情况。因此，我们研究了在含有不同类型无菌淡水的微观世界中的分批培养生长情况。用水样接种低起始细胞浓度的大肠杆菌O157（3×10³个细胞/毫升），并使用核酸染色结合流式细胞术跟踪其生长。我们证明，大肠杆菌O157能够在低碳浓度的无菌淡水中生长，这与通常认为添加到淡水样品中细胞数量会随时间下降的观点相反。建立了表观可同化有机碳（AOC(app)）浓度与大肠杆菌O157达到的最终细胞浓度之间的相关性（P < 0.01）。大肠杆菌O157利用了相当一部分AOC(app)（34±13%），但与源自天然淡水的细菌AOC测试群落相比，细胞数量产量约低五倍。平均而言，在30℃无菌淡水中生长的大肠杆菌O157的最大比生长速率（μ(max)）为0.19±0.07 h⁻¹。在五个不同温度下的分批培养试验表明，温度对大肠杆菌O157的μ(max)有积极影响。这些结果提供了关于这种常见病原体在水生环境中行为的新信息，并有助于进行微生物风险评估，以防止水传播疾病的传播。
