Salmonella Genomic Island 3 Is an Integrative and Conjugative Element and Contributes to Copper and Arsenic Tolerance of Salmonella enterica
Salmonella Genomic Island 3 Is an Integrative and Conjugative Element and Contributes to Copper and Arsenic Tolerance of Salmonella enterica
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DOI：
10.1128/aac.00429-19
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发表时间：
2019-09-01
影响因子：
4.9
通讯作者：
Akiba, Masato
中科院分区：
文献类型：
--
作者：
Arai, Nobuo;Sekizuka, Tsuyoshi;Akiba, Masato
沙门氏菌基因组岛 3 (SGI3) 首次被描述为沙门氏菌 4,[5], 12:i:- 中的染色体岛，沙门氏菌是肠沙门氏菌亚种的单相变体。鼠伤寒肠血清型。从日本分离的沙门氏菌 4,[5], 12:i:-中检测到的 SGI3 DNA 序列与之前报道的全长 81 kb 的序列相同。 SGI3由86个开放阅读框组成，包括一个铜稳态和银抗性岛（CHASRI）和一个砷耐受操纵子，此外还有与接合转移和DNA复制或分配相关的基因，表明该岛是一个可移动的遗传元件。我们使用鼠伤寒沙门氏菌、海德堡、Hadar、Newport、Cerro 和 Thompson 作为受体进行过滤交配实验，成功地选择了获得 SGI3 的转接合子。使用 I-CeuI 消化的基因组 DNA 进行的 Southern 印迹分析表明，SGI3 已整合到转接合子的染色体片段中。 PCR和测序分析表明SGI3被插入到tRNA基因pheV或pheR的3'端。目标位点的长度为52或55 bp，并且还检测到表明生成SGI3的环状形式的55 bp attI序列。在厌氧条件下，与受体菌株相比，转接合子对 CuSO4 具有更高的 MIC。耐受性由 CHASRI 中的 cus 基因簇定义。在有氧条件下，与受体菌株相比，转接合子对 Na2HAsO4 的 MIC 也明显更高。这些发现清楚地表明，SGI3 是一种整合和接合元素，有助于肠沙门氏菌对铜和砷的耐受性。
Salmonella genomic island 3 (SGI3) was first described as a chromosomal island in Salmonella 4,[5], 12:i:-, a monophasic variant of Salmonella enterica subsp. enterica serovar Typhimurium. The SGI3 DNA sequence detected from Salmonella 4,[5], 12: i:-isolated in Japan was identical to that of a previously reported one across entire length of 81 kb. SGI3 consists of 86 open reading frames, including a copper homeostasis and silver resistance island (CHASRI) and an arsenic tolerance operon, in addition to genes related to conjugative transfer and DNA replication or partitioning, suggesting that the island is a mobile genetic element. We successfully selected transconjugants that acquired SGI3 after filter-mating experiments using the S. enterica serovars Typhimurium, Heidelberg, Hadar, Newport, Cerro, and Thompson as recipients. Southern blot analysis using I-CeuI-digested genomic DNA demonstrated that SGI3 was integrated into a chromosomal fragment of the transconjugants. PCR and sequencing analysis demonstrated that SGI3 was inserted into the 3' end of the tRNA genes pheV or pheR. The length of the target site was 52 or 55 bp, and a 55-bp attI sequence indicating generation of the circular form of SGI3 was also detected. The transconjugants had a higher MIC against CuSO4 compared to the recipient strains under anaerobic conditions. Tolerance was defined by the cus gene cluster in the CHASRI. The transconjugants also had distinctly higher MICs against Na2HAsO4 compared to recipient strains under aerobic conditions. These findings clearly demonstrate that SGI3 is an integrative and conjugative element and contributes to the copper and arsenic tolerance of S. enterica.