Hong Hyerim, Jung Jaejoon, Park Woojun
Department of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea.
PLoS One. 2014 Sep 17;9(9):e107716. doi: 10.1371/journal.pone.0107716. eCollection 2014.
Acquisition of the extracellular tetracycline (TC) resistance plasmid pAST2 affected host gene expression and phenotype in the oil-degrading soil bacterium, Acinetobacter oleivorans DR1. Whole-transcriptome profiling of DR1 cells harboring pAST2 revealed that all the plasmid genes were highly expressed under TC conditions, and the expression levels of many host chromosomal genes were modulated by the presence of pAST2. The host energy burden imposed by replication of pAST2 led to (i) lowered ATP concentrations, (ii) downregulated expression of many genes involved in cellular growth, and (iii) reduced growth rate. Interestingly, some phenotypes were restored by deleting the plasmid-encoded efflux pump gene tetH, suggesting that the membrane integrity changes resulting from the incorporation of efflux pump proteins also resulted in altered host response under the tested conditions. Alteration of membrane integrity by tetH deletion was shown by measuring permeability of fluorescent probe and membrane hydrophobicity. The presence of the plasmid conferred peroxide and superoxide resistance to cells, but only peroxide resistance was diminished by tetH gene deletion, suggesting that the plasmid-encoded membrane-bound efflux pump protein provided peroxide resistance. The downregulation of fimbriae-related genes presumably led to reduced swimming motility, but this phenotype was recovered by tetH gene deletion. Our data suggest that not only the plasmid replication burden, but also its encoded efflux pump protein altered host chromosomal gene expression and phenotype, which also alters the ecological fitness of the host in the environment.
获得细胞外四环素（TC）抗性质粒pAST2影响了石油降解土壤细菌食油不动杆菌DR1的宿主基因表达和表型。对携带pAST2的DR1细胞进行全转录组分析发现，所有质粒基因在TC条件下均高度表达，并且许多宿主染色体基因的表达水平受到pAST2存在的调节。pAST2复制给宿主带来的能量负担导致：（i）ATP浓度降低；（ii）许多参与细胞生长的基因表达下调；（iii）生长速率降低。有趣的是，通过缺失质粒编码的外排泵基因tetH可恢复一些表型，这表明外排泵蛋白的整合导致的膜完整性变化也导致了在测试条件下宿主反应的改变。通过测量荧光探针的通透性和膜疏水性表明tetH缺失改变了膜完整性。质粒的存在赋予细胞对过氧化物和超氧化物的抗性，但tetH基因缺失仅降低了对过氧化物的抗性，这表明质粒编码的膜结合外排泵蛋白提供了对过氧化物的抗性。菌毛相关基因的下调可能导致游动能力降低，但这种表型可通过tetH基因缺失恢复。我们的数据表明，不仅质粒复制负担，而且其编码的外排泵蛋白都会改变宿主染色体基因表达和表型，这也会改变宿主在环境中的生态适应性。
