Unit of Microbiology, Belgian Nuclear Research Centre (SCK•CEN), B-2400 Mol, Belgium.
Plasmid. 2011 May;65(3):193-203. doi: 10.1016/j.plasmid.2010.12.006. Epub 2010 Dec 24.
Cupriavidus metallidurans CH34 is a β-proteobacterium well equipped to cope with harsh environmental conditions such as heavy metal pollution. The strain carries two megaplasmids specialized in the response to heavy metals and a considerable number of genomic islands, transposons and insertion sequence (IS) elements. The latter were characterized in detail in this study, which revealed nine new IS elements totaling to 21 distinct IS elements from 10 different IS families and reaching a total of 57 intact IS copies in CH34. Analysis of all fully sequenced bacterial genomes revealed that relatives of these IS elements were mostly found in the Burkholderiaceae family (β-proteobacteria) to which C. metallidurans belongs. Three IS elements were 100% conserved in other bacteria suggesting recent interaction and horizontal transfer between these strains. In addition, a number of these IS elements were associated with genomic islands, gene inactivation or rearrangements that alter the autotrophic growth capacities of CH34. The latter rearrangements gave the first molecular evidence for the mutator phenotype that is characteristic for various C. metallidurans strains. Furthermore, differential expression of some IS elements (or adjacent genes in the same strand orientation) was found under heavy metal stress, an environmental stress to which C. metallidurans CH34 is well adapted. These observations indicate that these IS elements play an active role in C. metallidurans CH34 lifestyle, including its metabolic potential and adaptation under selective pressure.
金属铜菌（Cupriavidus metallidurans）CH34 是一种β变形菌，能够很好地应对恶劣的环境条件，如重金属污染。该菌株携带两个专门用于应对重金属的大型质粒和相当数量的基因组岛、转座子和插入序列（IS）元件。本研究详细描述了后者，揭示了 9 个新的 IS 元件，共计来自 10 个不同 IS 家族的 21 个不同 IS 元件，在 CH34 中总共有 57 个完整的 IS 拷贝。对所有全序列细菌基因组的分析表明，这些 IS 元件的亲缘关系主要存在于β变形菌的伯克霍尔德氏菌科（Burkholderiaceae）中，金属铜菌就属于该科。有 3 个 IS 元件在其他细菌中 100%保守，这表明这些菌株之间最近发生了相互作用和水平转移。此外，这些 IS 元件中的许多与基因组岛、基因失活或重排有关，这些重排改变了 CH34 的自养生长能力。后者的重排为各种金属铜菌菌株所具有的突变表型提供了第一个分子证据。此外，在重金属胁迫下，一些 IS 元件（或同一链向上相邻基因）的表达存在差异，金属铜菌 CH34 对这种环境胁迫有很好的适应性。这些观察表明，这些 IS 元件在金属铜菌 CH34 的生活方式中发挥着积极的作用，包括其代谢潜力和在选择压力下的适应能力。
