Mohd-Zain Zaini, Turner Sarah L, Cerdeño-Tárraga Ana M, Lilley Andrew K, Inzana Thomas J, Duncan A Jane, Harding Rosalind M, Hood Derek W, Peto Timothy E, Crook Derrick W
Infectious Diseases and Clinical Microbiology, John Radcliffe Hospital, University of Oxford, Headington, Oxford, OX3 9DU, UK.
J Bacteriol. 2004 Dec;186(23):8114-22. doi: 10.1128/JB.186.23.8114-8122.2004.
Transferable antibiotic resistance in Haemophilus influenzae was first detected in the early 1970s. After this, resistance spread rapidly worldwide and was shown to be transferred by a large 40- to 60-kb conjugative element. Bioinformatics analysis of the complete sequence of a typical H. influenzae conjugative resistance element, ICEHin1056, revealed the shared evolutionary origin of this element. ICEHin1056 has homology to 20 contiguous sequences in the National Center for Biotechnology Information database. Systematic comparison of these homologous sequences resulted in identification of a conserved syntenic genomic island consisting of up to 33 core genes in 16 beta- and gamma-Proteobacteria. These diverse genomic islands shared a common evolutionary origin, insert into tRNA genes, and have diverged widely, with G+C contents ranging from 40 to 70% and amino acid homologies as low as 20 to 25% for shared core genes. These core genes are likely to account for the conjugative transfer of the genomic islands and may even encode autonomous replication. Accessory gene clusters were nestled among the core genes and encode the following diverse major attributes: antibiotic, metal, and antiseptic resistance; degradation of chemicals; type IV secretion systems; two-component signaling systems; Vi antigen capsule synthesis; toxin production; and a wide range of metabolic functions. These related genomic islands include the following well-characterized structures: SPI-7, found in Salmonella enterica serovar Typhi; PAP1 or pKLC102, found in Pseudomonas aeruginosa; and the clc element, found in Pseudomonas sp. strain B13. This is the first report of a diverse family of related syntenic genomic islands with a deep evolutionary origin, and our findings challenge the view that genomic islands consist only of independently evolving modules.
20世纪70年代初首次在流感嗜血杆菌中检测到可转移的抗生素耐药性。此后，耐药性在全球迅速传播，并被证明是由一个40至60kb的大型接合元件转移的。对典型的流感嗜血杆菌接合耐药元件ICEHin1056的完整序列进行生物信息学分析，揭示了该元件的共同进化起源。ICEHin1056与美国国立生物技术信息中心数据库中的20个连续序列具有同源性。对这些同源序列进行系统比较，发现了一个保守的同线基因组岛，该岛由16个β-和γ-变形杆菌中的多达33个核心基因组成。这些不同的基因组岛具有共同的进化起源，插入tRNA基因，并且差异很大，其G+C含量在40%至70%之间，共享核心基因的氨基酸同源性低至20%至25%。这些核心基因可能是基因组岛接合转移的原因，甚至可能编码自主复制。辅助基因簇位于核心基因之间，编码以下多种主要特性：抗生素、金属和防腐剂耐药性；化学物质降解；IV型分泌系统；双组分信号系统；Vi抗原荚膜合成；毒素产生；以及广泛的代谢功能。这些相关的基因组岛包括以下特征明确的结构：在伤寒沙门氏菌血清型伤寒中发现的SPI-7；在铜绿假单胞菌中发现的PAP1或pKLC102；以及在假单胞菌属菌株B13中发现的clc元件。这是关于一个具有深厚进化起源的相关同线基因组岛多样家族的首次报道，我们的发现挑战了基因组岛仅由独立进化模块组成的观点。
