Streit W R, Phillips D A
Department of Agronomy and Range Science, University of California, Davis 95616, USA.
Appl Environ Microbiol. 1996 Sep;62(9):3333-8. doi: 10.1128/aem.62.9.3333-3338.1996.
The growth of Rhizobium meliloti 1021 in an experimental alfalfa (Medicago sativa L.) rhizosphere was stimulated by adding nanomolar amounts of biotin. To overcome this biotin limitation, R. meliloti strains were constructed by conjugating the Escherichia coli biotin synthesis operon into biotin auxotroph R. meliloti 1021-B3. Transconjugant strains Rm1021-WS10 and Rm1021-WS11 grew faster in vitro and achieved a higher cell density than did R. meliloti 1021 and overproduced biotin on a defined medium. The increase in cell yield was associated with as much as a 99% loss in viability for Rm1021-WS11, but data suggested that a separate stabilizing factor in the E. coli DNA reduced cell death in Rm1021-WS10. In rhizosphere tests, the recombinant strains showed delayed growth and competed poorly against Rm1021.
添加纳摩尔量的生物素可刺激苜蓿中华根瘤菌1021在实验性苜蓿（紫花苜蓿）根际的生长。为克服这种生物素限制，通过将大肠杆菌生物素合成操纵子与生物素营养缺陷型苜蓿中华根瘤菌1021 - B3进行接合，构建了苜蓿中华根瘤菌菌株。转接合子菌株Rm1021 - WS10和Rm1021 - WS11在体外生长更快，细胞密度高于苜蓿中华根瘤菌1021，并且在限定培养基上生物素过量产生。细胞产量的增加与Rm1021 - WS11高达99%的活力丧失有关，但数据表明大肠杆菌DNA中的一个单独稳定因子减少了Rm1021 - WS10中的细胞死亡。在根际试验中，重组菌株生长延迟，与Rm1021竞争能力差。
