Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA, United States.
Front Cell Infect Microbiol. 2018 Jul 11;8:213. doi: 10.3389/fcimb.2018.00213. eCollection 2018.
Cyclic-di-GMP (c-di-GMP) contributes to the regulation of processes required by the Lyme disease (LD) spirochetes to complete the tick-mammal enzootic cycle. Our understanding of the effector mechanisms of c-di-GMP in the is evolving. While most LD spirochete isolates encode a single PilZ domain containing c-di-GMP receptor designated as PlzA, genome analyses have revealed that a subset encode a second PilZ domain protein (PlzB). The c-di-GMP binding potential of PlzB, and its role in LD spirochete biology, have not been investigated. To determine if PlzB binds c-di-GMP, from isolate ZS7 was PCR amplified, cloned, and recombinant protein generated. PlzB bound c-di-GMP but not other nucleotides, indicating a specific binding interaction. To determine if PlzA and PlzB are functionally synonymous, a series of allelic-exchange gene deletion and -complemented strains were generated in the B31 background. B31-Δ was competent to infect larvae but not mice when delivered by either needle or tick feeding. B31-Δ also displayed an atypical motility phenotype. Complementation in of B31-Δ with (B31- KI) restored wild-type (wt) phenotype. However, a strain complemented in with (B31- KI) did not. The data presented here are consistent with an earlier study that demonstrated that PlzA plays an essential role in spirochete survival in the mammalian environment. We add to our understanding of the c-di-GMP regulatory network by demonstrating that while PlzB binds c-di-GMP, it is not functionally synonymous with PlzA. The absence of from most strains suggests that it is not required for survival. One possibility is that cells that harbor both PlzA and PlzB might have enhanced biological fitness or increased virulence.
环二鸟苷酸 (c-di-GMP) 有助于调节莱姆病 (LD) 螺旋体完成蜱-哺乳动物生态循环所需的过程。我们对 c-di-GMP 在螺旋体中的效应机制的理解正在不断发展。虽然大多数 LD 螺旋体分离株编码一个单一的 PilZ 结构域，包含一个指定为 PlzA 的 c-di-GMP 受体，但基因组分析表明，一部分编码第二个 PilZ 结构域蛋白 (PlzB)。PlzB 与 c-di-GMP 的结合潜力及其在 LD 螺旋体生物学中的作用尚未得到研究。为了确定 PlzB 是否结合 c-di-GMP，从 ZS7 分离株中扩增、克隆和生成重组蛋白。PlzB 结合 c-di-GMP 但不结合其他核苷酸，表明存在特异性结合相互作用。为了确定 PlzA 和 PlzB 是否具有功能上的同义性，在 B31 背景下生成了一系列等位基因交换基因缺失和互补菌株。通过针或蜱喂食，B31-Δ 能够感染 幼虫，但不能感染小鼠。B31-Δ 还表现出非典型的运动表型。在 B31-Δ 中用 互补（B31-KI）恢复了野生型（wt）表型。然而，用 互补（B31-KI）的 B31-Δ 菌株则没有。这里呈现的数据与早期的一项研究一致，该研究表明 PlzA 在螺旋体在哺乳动物环境中的存活中发挥着重要作用。我们通过证明 PlzB 虽然结合 c-di-GMP，但与 PlzA 不是功能上的同义，从而加深了我们对 c-di-GMP 调节网络的理解。大多数菌株中没有 ，这表明它不是生存所必需的。一种可能性是，同时含有 PlzA 和 PlzB 的细胞可能具有增强的生物学适应性或增加的毒力。
