Chatterjee A K
J Bacteriol. 1980 Apr;142(1):111-9. doi: 10.1128/jb.142.1.111-119.1980.
R plasmid R68.45 was transferred in broth matings from Escherichia coli to strains of Erwinia amylovora, E. carotovora subsp. atroseptica, E. chrysanthemi, and E. herbicola (Enterobacter agglomerans); the frequency of transfer ranged from 2 x 10(-8) to 5 x 10(-4) per input donor cell depending on the bacterial species. The drug resistance markers tet(+), amp(+), and kan(+) were stable in these Erwinia species. Transconjugants of Erwinia spp., but not of the wild-type parent Erwinia strains, acquired levels of antibiotic resistance (tetracycline, 50 mug/ml; ampicillin, 200 mug/ml; kanamycin 200 mug/ml) similar to those of the donor R68.45-bearing strain of Escherichia coli. Erwinia transconjugants (with one exception of E. carotovora subsp. atroseptica) were donors of the antibiotic resistance markers; the frequency of transfer was consistently higher with an E. coli strain than with Erwinia spp. as recipients, and when matings were done on a solid surface (membranes) rather than in liquid. Transfer of chromosomal markers ade(+), gal(+), gtu(+) (utilization of galacturonate), his(+), leu(+), lys(+), thr(+), and trp(+) occurred in crosses between E. chrysanthemi strains harboring R68.45 and appropriate recipient strains; the frequency of transfer ranged from 9.0 x 10(-8) to 2.0 x 10(-6) depending on the selective marker. Analysis of the coinheritance of unselected markers among various classes of recombinants revealed linkage between thr-leu-lys-ade and between trp and his, thus confirming earlier findings with the Hfr-type donor cells. Since R68.45 mobilized an array of chromosomal markers in the wild-type as well as genetically marked strains of E. chrysanthemi, the system, used in conjunction with the existing Hfr strains, should provide a useful tool to study the genetics of plant pathogenicity of this bacterial species. In contrast to E. chrysanthemi, R68.45 did not mobilize chromosomal markers ilv(+), his(+), rbs(+), ser(+), and thr(+) in E. amylovora EA178.
R质粒R68.45在肉汤交配中从大肠杆菌转移至梨火疫病菌、胡萝卜软腐欧文氏菌黑胫亚种、菊欧文氏菌和草生欧文氏菌（成团肠杆菌）菌株；转移频率根据细菌种类不同，每输入一个供体细胞为2×10⁻⁸至5×10⁻⁴。耐药标记tet⁺、amp⁺和kan⁺在这些欧文氏菌属中是稳定的。欧文氏菌属的接合子，而非野生型亲本欧文氏菌菌株，获得的抗生素抗性水平（四环素，50μg/ml；氨苄青霉素，200μg/ml；卡那霉素，200μg/ml）与携带R68.45的供体大肠杆菌菌株相似。欧文氏菌接合子（胡萝卜软腐欧文氏菌黑胫亚种有一个例外）是抗生素抗性标记的供体；以大肠杆菌菌株作为受体时的转移频率始终高于以欧文氏菌属作为受体，并且当在固体表面（膜）而非液体中进行交配时也是如此。在携带R68.45的菊欧文氏菌菌株与合适的受体菌株之间的杂交中发生了染色体标记ade⁺、gal⁺、gtu⁺（利用半乳糖醛酸）、his⁺、leu⁺、lys⁺、thr⁺和trp⁺的转移；转移频率根据选择标记不同为9.0×10⁻⁸至2.0×10⁻⁶。对各类重组体中未选择标记的共遗传分析揭示了thr - leu - lys - ade之间以及trp和his之间的连锁，从而证实了早期用Hfr型供体细胞得到的结果。由于R68.45在野生型以及经基因标记的菊欧文氏菌菌株中能调动一系列染色体标记，该系统与现有的Hfr菌株结合使用，应能为研究这种细菌的植物致病性遗传学提供一个有用的工具。与菊欧文氏菌不同，R68.45在梨火疫病菌EA178中不能调动染色体标记ilv⁺、his⁺、rbs⁺、ser⁺和thr⁺。
