Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, University of Dublin, Trinity College Dublin, Dublin 2, Ireland.
Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental University Hospital, University of Dublin, Trinity College Dublin, Dublin 2, Ireland.
Infect Genet Evol. 2019 Jul;71:51-53. doi: 10.1016/j.meegid.2019.03.008. Epub 2019 Mar 18.
The arginine catabolic mobile element (ACME) was first described in methicillin-resistant Staphylococcus aureus and is considered to enhance transmission, persistence and survival. Subsequently ACMEs were shown to be more prevalent in the coagulase-negative Staphylococcus epidermidis. Previously, ACME types were distinguished by characteristic combinations of the arc and opp3 operons [I (arc+, opp3+), II (arc+, opp3-) and III (arc-, opp3+)] encoding an arginine deaminase pathway and oligopeptide permease transporter, respectively. Recently two novel ACME types harboring the potassium transporter-encoding operon kdp were described in oral S. epidermidis isolates [IV (arc+, opp3-, kdp+), and V (arc+, opp3+, kdp+)]. This study investigated two independent oral S. epidermidis isolates that yielded amplimers with kdp-directed primers only when subjected to ACME typing PCRs. Hybrid assemblies based on Illumina MiSeq short-read and Oxford Nanopore MinION long-read whole genome sequences revealed that both isolates harbored a sixth, novel ACME type (VI) integrated into orfX. Both ACME VIs lacked the arc and opp3 operons, harbored the kdp operon adjacent to other commonly ACME-associated genes including speG, hsd, sdr, and rep, but the structural organization of the adjacent regions were distinct. These ACMEs were flanked by different direct repeat sequences and the ACME VI-positive isolates belonged to unrelated genetic clusters. Overall these findings are indicative of independent evolution. The identification of ACME type VI further illustrates the diversity of ACME elements in S. epidermidis. The presence of ACMEs harboring kdp may confer a selective advantage on oral S. epidermidis in a potassium-rich environment such as found in dental plaque.
精氨酸分解移动元件（ACME）最初在耐甲氧西林金黄色葡萄球菌中被描述，被认为可增强传播、持久性和生存能力。随后发现 ACME 在凝固酶阴性表皮葡萄球菌中更为普遍。先前，ACME 类型通过特征性的 arc 和 opp3 操纵子组合来区分 [I（arc+，opp3+）、II（arc+，opp3-）和 III（arc-，opp3+）]，分别编码精氨酸脱氨酶途径和寡肽渗透转运体。最近，在口腔表皮葡萄球菌分离株中描述了两种携带钾转运蛋白编码操纵子 kdp 的新型 ACME 类型 [IV（arc+，opp3-，kdp+）和 V（arc+，opp3+，kdp+）]。本研究调查了两个独立的口腔表皮葡萄球菌分离株，只有在进行 ACME 分型 PCR 时，这些分离株才会产生带有 kdp 定向引物的扩增子。基于 Illumina MiSeq 短读和 Oxford Nanopore MinION 长读全基因组序列的杂交组装表明，这两个分离株都携带有一个第六种新型 ACME 类型（VI），整合到 orfX 中。ACME VIs 均缺失 arc 和 opp3 操纵子，携带 kdp 操纵子，紧邻其他常见的 ACME 相关基因，包括 speG、hsd、sdr 和 rep，但相邻区域的结构组织不同。这些 ACME 由不同的直接重复序列侧翼，ACME VI 阳性分离株属于无关的遗传簇。总体而言，这些发现表明了独立进化。ACME 类型 VI 的鉴定进一步说明了表皮葡萄球菌中 ACME 元件的多样性。在富含钾的环境（如牙菌斑中）中，携带 kdp 的 ACME 的存在可能为口腔表皮葡萄球菌提供了选择性优势。
