The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA.
BMC Microbiol. 2011 Feb 8;11:31. doi: 10.1186/1471-2180-11-31.
Salmonella has been employed to deliver therapeutic molecules against cancer and infectious diseases. As the carrier for target gene(s), the cargo plasmid should be stable in the bacterial vector. Plasmid recombination has been reduced in E. coli by mutating several genes including the recA, recE, recF and recJ. However, to our knowledge, there have been no published studies of the effect of these or any other genes that play a role in plasmid recombination in Salmonella enterica.
The effect of recA, recF and recJ deletions on DNA recombination was examined in three serotypes of Salmonella enterica. We found that (1) intraplasmid recombination between direct duplications was RecF-independent in Typhimurium and Paratyphi A, but could be significantly reduced in Typhi by a ΔrecA or ΔrecF mutation; (2) in all three Salmonella serotypes, both ΔrecA and ΔrecF mutations reduced intraplasmid recombination when a 1041 bp intervening sequence was present between the duplications; (3) ΔrecA and ΔrecF mutations resulted in lower frequencies of interplasmid recombination in Typhimurium and Paratyphi A, but not in Typhi; (4) in some cases, a ΔrecJ mutation could reduce plasmid recombination but was less effective than ΔrecA and ΔrecF mutations. We also examined chromosome-related recombination. The frequencies of intrachromosomal recombination and plasmid integration into the chromosome were 2 and 3 logs lower than plasmid recombination frequencies in Rec+ strains. A ΔrecA mutation reduced both intrachromosomal recombination and plasmid integration frequencies.
The ΔrecA and ΔrecF mutations can reduce plasmid recombination frequencies in Salmonella enterica, but the effect can vary between serovars. This information will be useful for developing Salmonella delivery vectors able to stably maintain plasmid cargoes for vaccine development and gene therapy.
沙门氏菌已被用于递送针对癌症和传染病的治疗分子。作为靶基因的载体，货物质粒应在细菌载体中稳定。通过突变包括 recA、recE、recF 和 recJ 在内的几个基因，已经减少了大肠杆菌中的质粒重组。然而，据我们所知，还没有关于这些或任何其他在沙门氏菌 enterica 中发挥质粒重组作用的基因的影响的已发表研究。
在三种血清型的沙门氏菌 enterica 中，研究了 recA、recF 和 recJ 缺失对 DNA 重组的影响。我们发现：(1) 在 Typhimurium 和 Paratyphi A 中，直接重复之间的质粒内重组与 RecF 无关，但 Typhi 中的 recA 或 recF 突变可显著减少；(2) 在所有三种沙门氏菌血清型中，当重复之间存在 1041bp 的插入序列时，ΔrecA 和 ΔrecF 突变均降低了质粒内重组；(3) ΔrecA 和 ΔrecF 突变导致 Typhimurium 和 Paratyphi A 中的质粒间重组频率降低，但 Typhi 中则不然；(4) 在某些情况下，ΔrecJ 突变可降低质粒重组，但不如 ΔrecA 和 ΔrecF 突变有效。我们还检查了染色体相关的重组。染色体内重组和质粒整合到染色体中的频率比 Rec+ 菌株中的质粒重组频率低 2 和 3 个对数。ΔrecA 突变降低了染色体内重组和质粒整合的频率。
ΔrecA 和 ΔrecF 突变可降低沙门氏菌 enterica 中的质粒重组频率，但在血清型之间的效果可能有所不同。这些信息对于开发能够稳定维持质粒货物的沙门氏菌递送载体用于疫苗开发和基因治疗将是有用的。
