Daane L L, Molina J A, Berry E C, Sadowsky M J
Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul 55108, USA.
Appl Environ Microbiol. 1996 Feb;62(2):515-21. doi: 10.1128/aem.62.2.515-521.1996.
We have developed a model system to assess the influence of earthworm activity on the transfer of plasmid pJP4 from an inoculated donor bacterium, Pseudomonas fluorescens C5t (pJP4), to indigenous soil microorganisms. Three different earthworm species (Lumbricus terrestris, Lumbricus rubellus, and Aporrectodea trapezoides), each with unique burrowing, casting, and feeding behaviors, were evaluated. Soil columns were inoculated on the surface with 10(8) cells per g of soil of the donor bacterium, and after a 2-week incubation period, donor, transconjugant, and total bacteria were enumerated at 5-cm-depth intervals. Transconjugants were confirmed by use of colony hybridization with a mer gene probe. In situ gene transfer of plasmid pJP4 from P. fluorescens C5t to indigenous soil bacteria was detected in all inoculated microcosms. In the absence of earthworms, the depth of recovery was limited to the top 5 cm of the column, with approximately 10(3) transconjugants per g of soil. However, the total number of transconjugants recovered from soil was significantly greater in microcosms containing either L. rubellus or A. trapezoides, with levels reaching about 10(5) CFU/g of soil. In addition, earthworms distributed donor and transconjugant bacteria throughout the microcosm columns, with the depth of recovery dependent on the burrowing behavior of each earthworm species. Donor and transconjugant bacteria were also recovered from earthworm casts and inside developing cocoons. Transconjugant bacteria from the indigenous soil microflora were classified as belonging to Acidovorax spp., Acinetobacter spp., Agrobacterium spp., Pasteurella spp., Pseudomonas spp., and Xanthomonas spp.
我们开发了一个模型系统，以评估蚯蚓活动对质粒pJP4从接种的供体细菌荧光假单胞菌C5t（pJP4）转移到本地土壤微生物的影响。评估了三种不同的蚯蚓物种（赤子爱胜蚓、红色爱胜蚓和梯形环毛蚓），每种蚯蚓都有独特的打洞、排粪和取食行为。在土壤柱表面接种每克土壤10⁸个供体细菌细胞，经过2周的培养期后，以5厘米深度间隔对供体菌、转接合子和总细菌进行计数。通过使用mer基因探针进行菌落杂交来确认转接合子。在所有接种的微观世界中都检测到了质粒pJP4从荧光假单胞菌C5t原位转移到本地土壤细菌。在没有蚯蚓的情况下，回收深度仅限于柱顶5厘米，每克土壤约有10³个转接合子。然而，在含有红色爱胜蚓或梯形环毛蚓的微观世界中，从土壤中回收的转接合子总数显著更多，水平达到约10⁵CFU/克土壤。此外，蚯蚓将供体菌和转接合子细菌分布在整个微观世界柱中，回收深度取决于每种蚯蚓的打洞行为。还从蚯蚓粪便和发育中的茧内回收了供体菌和转接合子细菌。来自本地土壤微生物群落的转接合子细菌被分类为属于嗜酸菌属、不动杆菌属、土壤杆菌属、巴斯德菌属、假单胞菌属和黄单胞菌属。
