Food Science and Human Nutrition Department, University of Florida, Gainesville, FL, USA.
J Appl Microbiol. 2021 Feb;130(2):416-423. doi: 10.1111/jam.14775. Epub 2020 Aug 3.
This research was performed to investigate the influence of clay and humic acid on Escherichia coli O157 survival in model soils. Additionally, the influence of pH and humic acid on E. coli O157 in liquid culture was investigated.
Artificial soil microcosms were prepared with sand, kaolinite, bentonite and humic acid. Artificial soil microcosms pH was adjusted (6·0-7·0) with aluminium sulphate before E. coli O157 inoculation. After 56 days of incubation at 30°C, significant differences in E. coli O157 log CFU per gram were observed between 0 and 1000 ppm (P < 0·0001) and 0 and 5000 ppm (P < 0·0001) humic acid in 1·5% clay soils, but not in 7·5 or 15% clay soils. Significant differences (P < 0·05) in E. coli O157 log CFU per ml were observed in liquid culture influenced by humic acid concentrations after 8 h at 37°C.
The developed model soils support E. coli O157 populations over 28 days, and higher clay soils may aid in E. coli O157 survival.
These results provide insights into physicochemical properties of soil that may influence E. coli O157 in the environment and help explain E. coli O157 survival in various soils and geographical regions.
本研究旨在探讨粘土和腐殖酸对大肠杆菌 O157 在模型土壤中存活的影响。此外，还研究了 pH 值和腐殖酸对液体培养大肠杆菌 O157 的影响。
用沙子、高岭土、膨润土和腐殖酸制备人工土壤微宇宙。在接种大肠杆菌 O157 之前，用硫酸铝调节人工土壤微宇宙的 pH 值（6.0-7.0）。在 30°C 下孵育 56 天后，在 1.5%粘土土壤中，0 至 1000 ppm（P < 0.0001）和 0 至 5000 ppm（P < 0.0001）腐殖酸之间观察到大肠杆菌 O157 每克菌落形成单位的 log CFU 存在显著差异，但在 7.5%或 15%的粘土土壤中则没有。在 37°C 孵育 8 小时后，在液体培养中观察到腐殖酸浓度对大肠杆菌 O157 每毫升菌落形成单位的 log CFU 存在显著差异（P < 0.05）。
所开发的模型土壤支持大肠杆菌 O157 种群存活 28 天以上，较高的粘土土壤可能有助于大肠杆菌 O157 的存活。
这些结果提供了对可能影响环境中大肠杆菌 O157 的土壤理化性质的深入了解，并有助于解释大肠杆菌 O157 在不同土壤和地理区域的存活情况。
