Plasmid transfer between introduced and indigenous bacteria in leaf litter, soil and vermicompost as affected by soil invertebrates

 Plasmid transfer between introduced strains of Pseudomonas stutzeri JM302 (pLV1013), Pseudomonas putida PAW340 (pLV1017), Pseudomonas aeruginosa PAO5 (RP4), and Enterobacter cloacae MF10 (RP4), all of them harbouring genetically modified or naturally occurring plasmids and bacteria indigenous to oak leaf litter, soddy-podzolic soil or vermicompost was monitored using non-sterile laboratory microcosms inhabited by the millipede Pachyiulus flavipes, the woodlouse Armadillidium vulgare, or the earthworms Aporrectodea caliginosa and Eisenia fetida, respectively. Plasmid transfer from genetically modified Streptococcus faecalis JH2-2 (pAMβ₁) to Bacillus thuringiensis var. israelensis 1-5 under similar conditions was also followed. A recombinant conjugative plasmid (pLV1017) encoding resistance to antibiotics and expressing catechol 2,3-dioxygenase was transferred into two facultatively anaerobic gram-negative bacteria, isolated from the excrement of A. vulgare. Presumed transconjugants of the facultatively anerobic gram-negative bacteria given above were isolated from the leaves and soil (four strains) and the excrement of the invertebrates (11 strains). They carried the same plasmids and exhibited the same enzymatic activity as the respective inoculant strains; for most of them, however, DNA fingerprints were slightly different. Transfer from S. faecalis JH2-2 to B. thuringiensis var. israelensis of a naturally occurring plasmid, pAMb₁, encoding resistance to erythromycin was observed in vermicompost. Received: 18 November 1997     

鸡致病性大肠杆菌的质粒DNA指纹图谱分析

从山东省诸城地区6个集约化养鸡场的大肠杆菌感染鸡群的死鸡、毛蛋的心血中分离到32株细菌,经形态、培养特性及生化反应鉴定为大肠埃希氏杆菌(Escherichia.coli)简称大肠杆菌(E.coli)。对其作动物回归试验结果表明,全部为致病性大肠杆菌。从而证明从死鸡(毛蛋)心血中分离到的大肠杆菌与其致病性密切相关。将分离到的鸡大肠杆菌的14株优势血清型菌株进行了质粒DNA分析,通过碱裂解法小量提取质粒,然后对质粒进行了琼脂糖凝胶电泳分析,用hindⅢ限制性内切酶对质粒进行了酶切分析,结果表明:质粒的得率为100%,来源相同的菌株具有相同或相似的质粒图谱,来源不同的菌株的质粒图谱一般不同。将血清型和质粒图谱比较发现:同一血清型可以有不同的质粒图谱,不同血清型可以有相似的质粒图谱,血清型与质粒图谱没有直接的联系。本试验同一来源菌株的质粒指纹图谱相同、但它们的血清型不一致的现象可作为自然条件下同一质粒在不同血清型大肠杆菌中扩散转化的一个分子生物学依据。     

菊欧氏杆菌细菌素的产生与质粒的关系

菊欧氏杆菌(Erwinia chrysanthemi)的菌株EchB3和EchR8,能产生广谱性的细菌素。对EchB3和EchR8,分别用吖啶橙、利福平、胸腺嘧啶饥饿以及高温作脱质粒处理能得到不产细菌素的去质粒菌株。不同方法提取质粒证明产细菌素的野生型菌株能在0.8％的琼脂糖凝胶上检测到分子量约为22kb的质粒带,而失去产细菌素活性的去质粒菌株则检测不到。因此认为菊欧氏杆菌细菌素的产生可能与质粒有关。