Mechanisms of propagation of antibiotic resistance-conferring mobile genetic elements in Enterobacteriaceae and Vibrionaceae

肠杆菌科和弧菌科中赋予抗生素抗性的可移动遗传元件的传播机制

• 批准号: RGPIN-2016-04365
• 负责人: Burrus, Vincent
• 金额: $ 3.21万
• 依托单位: Université de Sherbrooke
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=615016
• 关键词: Mechanisms; propagation; antibiotic; resistance; conferring

Knowledge of the genetic determinants and molecular mechanisms that drive the mobility of antibiotic resistance genes is essential to fight the emergence and spread of multidrug resistant bacteria. The integrative and conjugative elements of the SXT/R391 family (SRIs) and the conjugative plasmids of the A/C incompatibility group (ACPs), are major vectors of multidrug resistance genes in pathogenic Enterobacteriaceae and Vibrionaceae. SRIs is responsible for antibiotic resistance of the seventh pandemic lineage of Vibrio cholerae, the etiologic agent of cholera, which remains a major cause of mortality and morbidity on a global scale. Meanwhile, reports associating ACPs with extended-spectrum ß-lactamases and carbapenemases are unsettlingly rising worldwide in enteric pathogens recovered from the environment, food-producing animals, food products and humans. ACPs also facilitate the propagation of the multidrug resistance-conferring Salmonella Genomic Island 1 (SGI1). Because ACPs and SRIs derive from a common ancestor, they code for highly similar conjugative transfer machineries, which mediate the translocation of genetic material from donor to recipient cells. Currently, the molecular mechanisms mediating these transfers are not well understood. Translocation of ACP and SRI DNA is initiated at the origin of transfer (oriT) by the relaxase TraI and the auxiliary protein MobI, both encoded by ACPs and SRIs. TraI belongs to an atypical family of relaxases, which are predicted HD phosphodiesterases and seems to require a MobI-like auxiliary protein to function, suggesting a completely unique and novel mechanism of conjugative transfer initiation. We anticipate that TraI and MobI are key factors involved in the ACP-mediated transfer of genomic islands such as SGI1. The main goal of this proposal is to characterize the mechanism of conjugative transfer initiation of ACPs and SRIs, and the molecular interactions between the conjugative machinery of ACPs and genomic islands that they mobilize. More specifically, we propose to identify all the partner proteins that are involved in DNA processing at oriT. Moreover, we aim at discovering the protein translocation signals that allow recognition and secretion of proteins through the type IV secretion system encoded by ACPs and SRIs. We will also functionally map with single-nucleotide accuracy the oriT to determine what specific sequence features promote assembly of a high-order complex at this locus. Finally, we will investigate the interactions between the ACP-encoded relaxosome and genomic islands that are mobilized by ACPs. Our results will yield fundamental insights about the basic biology ACPs and SRIs, thereby providing the scientific community with strong foundations and new potential molecular targets that could be used for the development of tools aimed at tackling the progression of multidrug resistance.

了解驱动抗生素耐药基因迁移的遗传决定因素和分子机制对于对抗多重耐药细菌的出现和传播至关重要。SXT/R391家族的整合和共轭元件（SRIs）和A/C不相容群（ACPs）的共轭质粒是致病性肠杆菌科和弧菌科多药耐药基因的主要载体。SRIs是霍乱病原菌霍乱弧菌第七大流行谱系的抗生素耐药性的原因，霍乱仍然是全球范围内死亡和发病的主要原因。同时，令人不安的是，在世界范围内，从环境、食用动物、食品和人类中回收的肠道病原体中，将acp与广谱ß-内酰胺酶和碳青霉烯酶联系起来的报告正在增加。ACPs还促进了具有多重耐药能力的沙门氏菌基因组岛1 （SGI1）的繁殖。由于acp和sri来自一个共同的祖先，它们编码高度相似的共轭转移机制，介导遗传物质从供体细胞向受体细胞的易位。目前，介导这些转移的分子机制尚不清楚。ACP和SRI DNA的易位是由ACP和SRIs编码的松弛蛋白TraI和辅助蛋白MobI在转移起点（oriT）启动的。TraI属于一个非典型的松弛酶家族，它被预测为HD磷酸二酯酶，似乎需要一个mobi样的辅助蛋白来发挥作用，这表明一个完全独特和新颖的共轭转移起始机制。我们预计，TraI和MobI是acp介导的基因组岛（如SGI1）转移的关键因素。