The mismatch repair system (mutS and mutL) in Acinetobacter baylyi ADP1
The mismatch repair system (mutS and mutL) in Acinetobacter baylyi ADP1
复制标题
贝氏不动杆菌 ADP1 中的错配修复系统（mutS 和 mutL）。
DOI：
10.1186/s12866-020-01729-3
复制
发表时间：
2020-02-28
期刊：
影响因子：
4.2
通讯作者：
Hua, Xiaoting
中科院分区：
文献类型：
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作者：
Zhou, Hua;Zhang, Linyue;Hua, Xiaoting
背景贝氏不动杆菌ADP1是一种天然可转化的细菌，是高通量遗传分析的理想菌株。因此，ADP1可用于研究DNA错配修复，这是一种修复错配碱基的机制。我们利用MutS缺失突变体(XH439)和突变L缺失突变体(XH440)，构建了MutS突变L双缺失突变体(XH441)，以研究错配修复系统在贝氏沼虾中的作用。结果测定了紫外线照射后的存活率，并通过利福平耐药试验(Rif(R))和实验进化测定了野生型ADP1和突变型突变株的突变频率、突变率和突变谱。此外，还测定了ADP1及其三个突变体的基因组DNA转化效率。最后，测定了野生型菌株、构建的3个缺失突变体以及通过Rif(R)检测获得的利福平抗性突变体的相对生长速率。3个突变体的紫外线照射后存活率均高于野生型，其中双缺失突变体的存活率最高。在Rif(R)试验中，3个突变体的突变率高于ADP1，且倾向于过渡突变。在实验进化中，所有三个突变体都显示出更高的突变率。但在Rif(R)试验中，只有XH439和XH441的突变率高于野生型菌株。当供体DNA含有转移突变时，XH441的转化效率高于XH438。这三个突变体的生长速度都高于野生型，这四个菌株的生长速度几乎都高于它们的所有rpoB突变体。生长速率结果显示，rpoB不同的氨基酸突变导致利福平耐药突变株适合度不同程度的降低。然而，同一突变带来的适应度成本并不因菌株背景而异。结论MutS和MutL的失活增加了贝氏不动杆菌的突变率和突变频率，这可能有助于利福平耐药性的进化和获得。MutS的缺失也与突变率和频率的增加有关，这表明即使在没有MutS的情况下，MutL也可能被激活。首次建立了贝利沙门氏菌的适应成本与利福平耐药突变之间的关系。
Background Acinetobacter baylyi ADP1 is an ideal bacterial strain for high-throughput genetic analysis as the bacterium is naturally transformable. Thus, ADP1 can be used to investigate DNA mismatch repair, a mechanism for repairing mismatched bases. We used the mutS deletion mutant (XH439) and mutL deletion mutant (XH440), and constructed a mutS mutL double deletion mutant (XH441) to investigate the role of the mismatch repair system in A. baylyi. Results We determined the survival rates after UV irradiation and measured the mutation frequencies, rates and spectra of wild-type ADP1 and mutSL mutant via rifampin resistance assay (Rif (R) assay) and experimental evolution. In addition, transformation efficiencies of genomic DNA in ADP1 and its three mutants were determined. Lastly, the relative growth rates of the wild type strain, three constructed deletion mutants, as well as the rifampin resistant mutants obtained from Rif (R) assays, were measured. All three mutants had higher survival rates after UV irradiation than wild type, especially the double deletion mutant. Three mutants showed higher mutation frequencies than ADP1 and favored transition mutations in Rif (R) assay. All three mutants showed increased mutation rates in the experimental evolution. However, only XH439 and XH441 had higher mutation rates than the wild type strain in Rif (R) assay. XH441 showed higher transformation efficiency than XH438 when donor DNA harbored transition mutations. All three mutants showed higher growth rates than wild-type, and these four strains displayed higher growth rates than almost all their rpoB mutants. The growth rate results showed different amino acid mutations in rpoB resulted in different extents of reduction in the fitness of rifampin resistant mutants. However, the fitness cost brought by the same mutation did not vary with strain background. Conclusions We demonstrated that inactivation of both mutS and mutL increased the mutation rates and frequencies in A. baylyi, which would contribute to the evolution and acquirement of rifampicin resistance. The mutS deletion is also implicated in increased mutation rates and frequencies, suggesting that MutL may be activated even in the absence of mutS. The correlation between fitness cost and rifampin resistance mutations in A. baylyi is firstly established.