Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.
Genome Biol Evol. 2011;3:881-95. doi: 10.1093/gbe/evr078. Epub 2011 Aug 2.
Here we discuss the evolution of the northern Australian Staphylococcus aureus isolate MSHR1132 genome. MSHR1132 belongs to the divergent clonal complex 75 lineage. The average nucleotide divergence between orthologous genes in MSHR1132 and typical S. aureus is approximately sevenfold greater than the maximum divergence observed in this species to date. MSHR1132 has a small accessory genome, which includes the well-characterized genomic islands, νSAα and νSaβ, suggesting that these elements were acquired well before the expansion of the typical S. aureus population. Other mobile elements show mosaic structure (the prophage ϕSa3) or evidence of recent acquisition from a typical S. aureus lineage (SCCmec, ICE6013 and plasmid pMSHR1132). There are two differences in gene repertoire compared with typical S. aureus that may be significant clues as to the genetic basis underlying the successful emergence of S. aureus as a pathogen. First, MSHR1132 lacks the genes for production of staphyloxanthin, the carotenoid pigment that confers upon S. aureus its characteristic golden color and protects against oxidative stress. The lack of pigment was demonstrated in 126 of 126 CC75 isolates. Second, a mobile clustered regularly interspaced short palindromic repeat (CRISPR) element is inserted into orfX of MSHR1132. Although common in other staphylococcal species, these elements are very rare within S. aureus and may impact accessory genome acquisition. The CRISPR spacer sequences reveal a history of attempted invasion by known S. aureus mobile elements. There is a case for the creation of a new taxon to accommodate this and related isolates.
在这里，我们讨论了澳大利亚北部金黄色葡萄球菌分离株 MSHR1132 基因组的进化。MSHR1132 属于分化的克隆复合体 75 谱系。MSHR1132 中同源基因的平均核苷酸差异与典型金黄色葡萄球菌相比约大 7 倍，这是迄今为止该物种观察到的最大差异。MSHR1132 具有一个小的辅助基因组，其中包括特征明确的基因组岛 νSAα 和 νSaβ，表明这些元件是在典型金黄色葡萄球菌种群扩张之前获得的。其他移动元件显示出镶嵌结构（噬菌体 ϕSa3）或最近从典型金黄色葡萄球菌谱系获得的证据（SCCmec、ICE6013 和质粒 pMSHR1132）。与典型金黄色葡萄球菌相比，基因库有两个差异，这可能是金黄色葡萄球菌成功成为病原体的遗传基础的重要线索。首先，MSHR1132 缺乏产生金黄色素的基因，金黄色素是一种类胡萝卜素色素，赋予金黄色葡萄球菌其特征性的金黄色，并能抵抗氧化应激。在 126 个 CC75 分离株中，有 126 个都缺乏这种色素。其次，一个移动的成簇规则间隔短回文重复（CRISPR）元件插入到 MSHR1132 的 orfX 中。尽管在其他葡萄球菌物种中很常见，但这些元件在金黄色葡萄球菌中非常罕见，可能会影响辅助基因组的获得。CRISPR 间隔序列揭示了已知金黄色葡萄球菌移动元件试图入侵的历史。有理由创建一个新的分类单元来容纳这一和相关的分离株。
