Domestication and characterization of TM7-the most elusive oral phylum

摘要 该应用程序的总体目标是表征新发现的具有 在牙周炎和牙周炎中，基因组极少，而丰度增加。在上一次 资助周期，我们成功地培育并测序了未培育的TM7的第一个成员TM7x 来自人类的门。TM7x菌株在所有细菌中是独一无二的，它的尺寸非常小(200-300 nm)和 生活在宿主细菌的表面，这种关系在人类微生物群中从未报道过 或者在细菌领域。由于基因组高度简化，TM7x无法合成自己的任何氨基酸， 维生素或细胞壁的前体，必须寄生于影响其生长的其他口腔细菌。特别的 值得注意的是，TM7属于候选的Phyla Radiation(CPR)，这是最近发现的 包含已知细菌多样性的26%的域细菌，估计有70个未培养的叶霉 基因组减少了。到目前为止，TM7x仍然是唯一报道的整个CPR的培养代表， 使我们的团队处于独特的地位，能够在该领域取得重大进展，并促进基本 在这些超小型人类相关细菌上的发现，以及CPR组作为一个整体。 我们的初步数据显示，TM7x与其细菌宿主口腔放线菌之间的关系 溶齿菌XH001是一种高度受调控的共生相互作用，其中tm7x表现出共生 寄生阶段(与寄主共存)和致病寄生阶段(诱导寄主细胞死亡)。这种耐人寻味的关系 与在温带噬菌体及其宿主中观察到的类似，在那里噬菌体能够 在溶源循环和裂解循环之间切换，并导致生理和生态后果。在这 应用，我们的目标是实现以下两个目标。1)鉴定分子组成和调控 调控TM7x与其宿主关系的途径；2)调查 TM7x与。特别是，在细菌寄生虫中编码的杀死宿主的机制 基因组缩减从根本上来说既是新的，也是与临床相关的。感染和杀死多人的能力 细菌宿主可能允许TM7x影响口腔群落的动态和结构，从而调节 在健康和疾病期间，社区和影响微生物群。 这项研究的成功将极大地推动这些超小型细菌的开发研究领域， 扩大我们对在人类中发现的这种新的微生物共生的知识，以及 心肺复苏生物对口腔微生物生态的影响。

Abstract The overall goal of this application is to characterize newly discovered ultra-small parasitic bacteria that have extremely reduced genomes and show increased abundance in gingivitis and periodontitis. In the previous funding cycle, we successfully cultivated and sequenced TM7x, the first member of the uncultivated TM7 phylum from humans. Strain TM7x is unique among all bacteria, it has an ultrasmall size (200-300 nm) and lives on the surface of a host bacterium, a relationship that had never been reported in the human microbiome or in the Bacteria domain. With a highly-reduced genome, TM7x cannot synthesize any of its own amino acids, vitamins or cell wall precursors and must parasitize other oral bacteria which impacts their growth. Of particular note is that TM7 belongs to the Candidate Phyla Radiation (CPR), a recently discovered subdivision in the domain Bacteria that comprises >26% of the known bacterial diversity with an estimated 70 uncultivated Phyla with reduced genomes. To date, TM7x is still the only reported cultivated representative of the entire CPR, putting our team in a unique position to make significant advancements in the field and facilitate fundamental discoveries on these ultra-small human associated bacteria, as well as the CPR group as a whole. Our preliminary data revealed that the relationship of TM7x and its bacterial host, an oral Actinomyces odontolyticus strain XH001 is a highly-regulated symbiotic interaction in which TM7x displays both symbiotic phase (co-existing with host) and virulent parasitic phase (inducing host cell death). This intriguing relationship is similar to the one observed for temperate bacteriophages and their hosts where phages are capable of switching between lysogenic and lytic cycle, and entails physiological and ecological consequences. In this application, we aim to achieve the following two goals. 1) To identify the molecular components and regulatory pathways governing the relationship between TM7x and its host; 2) To investigate the range of bacteria that TM7x interacts with. In particular, the mechanism of host killing encoded within a bacterial parasite with a reduced genome is both fundamentally novel and clinically relevant. The ability to infect and kill multiple bacterial hosts may allow TM7x to influence the oral community dynamics and structure, thus modulating community and impacting microbiome during health and diseases. The success of the study would greatly advance the developing research field of these ultra-small bacteria, expand our knowledge on this novel microbial symbiosis found in humans, as well as the potential impact of CPR organisms on oral microbiome ecology.