Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan.
Division of Bacterial and Parasitic Disease, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
Antimicrob Agents Chemother. 2019 Aug 23;63(9). doi: 10.1128/AAC.00429-19. Print 2019 Sep.
genomic island 3 (SGI3) was first described as a chromosomal island in 4,[5],12:i:-, a monophasic variant of subsp. serovar Typhimurium. The SGI3 DNA sequence detected from 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 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 or The length of the target site was 52 or 55 bp, and a 55-bp sequence indicating generation of the circular form of SGI3 was also detected. The transconjugants had a higher MIC against CuSO compared to the recipient strains under anaerobic conditions. Tolerance was defined by the gene cluster in the CHASRI. The transconjugants also had distinctly higher MICs against NaHAsO 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 .
基因组岛 3（SGI3）最初在 4,[5],12:i:−中被描述为染色体岛，这是 副猪嗜血杆菌血清型 Typhimurium 的单相变体。从日本分离的 4,[5],12:i:-中检测到的 SGI3 DNA 序列与之前报道的全长 81kb 的序列完全相同。SGI3 由 86 个开放阅读框组成，包括铜稳态和银抗性岛（CHASRI）和砷耐受操纵子，以及与共轭转移和 DNA 复制或分配相关的基因，表明该岛是一个移动遗传元件。我们成功地选择了在使用 鼠伤寒沙门氏菌、海德堡、哈达尔、纽波特、塞罗和汤普森作为受体的滤过交配实验后获得 SGI3 的转导体。使用 I-CeuI 消化的基因组 DNA 进行的 Southern blot 分析表明，SGI3 整合到了转导体的染色体片段中。PCR 和测序分析表明，SGI3 插入到 tRNA 基因 或 的 3' 端。靶位点的长度为 52 或 55bp，还检测到表明 SGI3 生成环状形式的 55bp 序列。在厌氧条件下，与受体菌株相比，转导体对 CuSO 的 MIC 更高。耐受力由 CHASRI 中的基因簇定义。在有氧条件下，与受体菌株相比，转导体对 NaHAsO 的 MIC 也明显更高。这些发现清楚地表明，SGI3 是一个整合和共轭元件，有助于 的铜和砷耐受。
