Pedersen J C, Jacobsen C S
Department of Marine Ecology and Microbiology, National Environmental Research Institute, Roskilde, Denmark.
Appl Environ Microbiol. 1993 May;59(5):1560-4. doi: 10.1128/aem.59.5.1560-1564.1993.
A sandy loam soil near field capacity moisture content (psi = -0.050 MPa) or air dried (psi = -300 MPa) was inoculated with about 3 x 10(7) CFU of Enterobacter cloacae JP120 and Alcaligenes eutrophus AEO106(pRO101) per g and incubated in 40-g portions at 17 degrees C in closed or open Erlenmeyer flasks. In the field-moist soil, selective plating, direct viable counts, and DNA hybridization showed only minor changes in the numbers of E. cloacae and A. eutrophus cells with time (14 days), and the results obtained with the three detection methods generally agreed. In the air-dried soil, the majority of both bacteria were found as intact DNA-carrying cells that were neither culturable nor viable by the methods employed in this study. The numbers of culturable E. cloacae and A. eutrophus cells dropped to 10(5) and 10(2) CFU/g, respectively, 2 h after inoculation. Direct viable counts showed that only about 1% of the cells detected by immunofluorescence microscopy were viable, but a fraction of viable nonculturable cells of both bacteria was present. A. eutrophus did not tolerate desiccation as well as E. cloacae. Only a minor fraction of the two test organisms regained their culturability or viability after rewetting of the air-dried soil; the number of total heterotrophic culturable bacteria, however, increased more than 10-fold and reached 73% of the level found in the field-moist soil at day 14.
将接近田间持水量水分含量（psi = -0.050兆帕）或风干（psi = -300兆帕）的砂壤土每克接种约3×10⁷CFU的阴沟肠杆菌JP120和嗜水气单胞菌AEO106(pRO101)，以40克的量在17℃下于密闭或开口的锥形瓶中培养。在田间湿润的土壤中，选择性平板计数、直接活菌计数和DNA杂交显示，阴沟肠杆菌和嗜水气单胞菌细胞数量随时间（14天）仅有微小变化，三种检测方法得到的结果总体一致。在风干土壤中，两种细菌中的大多数都是携带完整DNA的细胞，用本研究采用的方法既不可培养也无活力。接种后2小时，可培养的阴沟肠杆菌和嗜水气单胞菌细胞数量分别降至10⁵和10²CFU/克。直接活菌计数显示，免疫荧光显微镜检测到的细胞中只有约1%有活力，但两种细菌都存在一部分活的不可培养细胞。嗜水气单胞菌不如阴沟肠杆菌耐受干燥。风干土壤重新湿润后，两种受试生物只有一小部分恢复了可培养性或活力；然而，总异养可培养细菌数量增加了10倍以上，在第14天达到田间湿润土壤中发现水平的73%。
