Daane L L, Häggblom M M
Biotechnology Center for Agriculture and the Environment, Cook College, Rutgers University, New Brunswick, New Jersey 08901-8520, USA.
Appl Environ Microbiol. 1999 Jun;65(6):2376-81. doi: 10.1128/AEM.65.6.2376-2381.1999.
Earthworm egg capsules (cocoons) may acquire bacteria from the environment in which they are produced. We found that Ralstonia eutropha (pJP4) can be recovered from Eisenia fetida cocoons formed in soil inoculated with this bacterium. Plasmid pJP4 contains the genes necessary for 2,4-dichlorophenoxyacetic acid (2,4-D) and 2, 4-dichlorophenol (2,4-DCP) degradation. In this study we determined that the presence of R. eutropha (pJP4) within the developing earthworm cocoon can influence the degradation and toxicity of 2,4-D and 2,4-DCP, respectively. The addition of cocoons containing R. eutropha (pJP4) at either low or high densities (10(2) or 10(5) CFU per cocoon, respectively) initiated degradation of 2,4-D in nonsterile soil microcosms. Loss of 2,4-D was observed within the first week of incubation, and respiking the soil with 2,4-D showed depletion within 24 h. Microbial analysis of the soil revealed the presence of approximately 10(4) CFU R. eutropha (pJP4) g-1 of soil. The toxicity of 2,4-DCP to developing earthworms was tested by using cocoons with or without R. eutropha (pJP4). Results showed that cocoons containing R. eutropha (pJP4) were able to tolerate higher levels of 2,4-DCP. Our results indicate that the biodegradation of 2, 4-DCP by R. eutropha (pJP4) within the cocoons may be the mechanism contributing to toxicity reduction. These results suggest that the microbiota may influence the survival of developing earthworms exposed to toxic chemicals. In addition, cocoons can be used as inoculants for the introduction into the environment of beneficial bacteria, such as strains with biodegradative capabilities.
蚯蚓卵茧（茧）可能会从其产生的环境中获取细菌。我们发现，在接种了该细菌的土壤中形成的赤子爱胜蚓茧中可以分离出真养产碱菌（pJP4）。质粒pJP4包含降解2,4-二氯苯氧基乙酸（2,4-D）和2,4-二氯苯酚（2,4-DCP）所需的基因。在本研究中，我们确定发育中的蚯蚓茧内存在真养产碱菌（pJP4）分别会影响2,4-D和2,4-DCP的降解和毒性。添加低密度或高密度（分别为每个茧10²或10⁵CFU）含有真养产碱菌（pJP4）的茧，会引发非无菌土壤微宇宙中2,4-D的降解。在培养的第一周内观察到2,4-D的损失，用2,4-D重新处理土壤后，24小时内就出现了消耗。对土壤进行微生物分析发现，每克土壤中大约存在10⁴CFU的真养产碱菌（pJP4）。通过使用含有或不含有真养产碱菌（pJP4）的茧来测试2,4-DCP对发育中蚯蚓的毒性。结果表明，含有真养产碱菌（pJP4）的茧能够耐受更高水平的2,4-DCP。我们的结果表明，茧内真养产碱菌（pJP4）对2,4-DCP的生物降解可能是毒性降低的机制。这些结果表明，微生物群可能会影响接触有毒化学物质的发育中蚯蚓的存活。此外，茧可以用作接种剂，将有益细菌引入环境，例如具有生物降解能力的菌株。
