葡萄球菌 GGDEF 结构域蛋白独立于环状二聚体 GMP 调节生物膜形成。,Journal of Bacteriology

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葡萄球菌 GGDEF 结构域蛋白独立于环状二聚体 GMP 调节生物膜形成。
Journal of Bacteriology ( IF 2.7 ) Pub Date : 2008-05-23 , DOI: 10.1128/jb.00375-08
Linda M Holland ₁ , Sinéad T O'Donnell , Dmitri A Ryjenkov , Larissa Gomelsky , Shawn R Slater , Paul D Fey , Mark Gomelsky , James P O'Gara

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环状二聚体 GMP (c-di-GMP) 是一种重要的生物膜调节剂，可通过变构激活胞外多糖生物合成酶。变形菌基因组通常编码多个含有 GGDEF 结构域的双鸟苷酸环化酶，负责 c-di-GMP 的合成。相比之下，在测序的葡萄球菌基因组中仅存在一种保守的 GGDEF 结构域蛋白 GdpS（用于来自葡萄球菌的 GGDEF 结构域蛋白）和具有高度修饰的 GGDEF 结构域的第二种蛋白 GdpP。在这里，我们调查了 GdpS 在表皮葡萄球菌生物膜形成中的作用。在静态和流动细胞条件下，gdpS 的失活损害了在补充有 NaCl 的培养基中生物膜的形成，而 gdpS 过表达补充了突变并增强了野生型生物膜的发育。GdpS 通过提高 icaADBC mRNA 水平来增加 icaADBC 编码的胞外多糖、聚-N-乙酰-氨基葡萄糖的产量。出乎意料的是，发现 c-di-GMP 合成与 GdpS 提高 icaADBC 表达的能力无关。对双鸟苷酸环化酶活性必不可少的 GGEEF 基序的诱变不会损害 GdpS，并且 GdpS 的 N 端片段缺乏 GGDEF 域，部分补充了 gdpS 突变。此外，反式表达的异源双鸟苷酸环化酶未能补充 gdpS 突变，并且从 GdpS 纯化的 GGDEF 域在体外没有双鸟苷酸环化酶活性。来自金黄色葡萄球菌的 gdpS 基因表现出与其表皮葡萄球菌直向同源物相似的特征，表明 GdpS 介导的信号转导在葡萄球菌中是保守的。所以，GdpS 通过一种新的 c-di-GMP 独立机制影响生物膜形成，该机制涉及增加的 icaADBC mRNA 水平和胞外多糖生物合成。我们的数据提出了葡萄球菌不能合成 c-di-GMP 并且只有 c-di-GMP 信号通路的残余物的可能性。

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A staphylococcal GGDEF domain protein regulates biofilm formation independently of cyclic dimeric GMP.

Cyclic dimeric GMP (c-di-GMP) is an important biofilm regulator that allosterically activates enzymes of exopolysaccharide biosynthesis. Proteobacterial genomes usually encode multiple GGDEF domain-containing diguanylate cyclases responsible for c-di-GMP synthesis. In contrast, only one conserved GGDEF domain protein, GdpS (for GGDEF domain protein from Staphylococcus), and a second protein with a highly modified GGDEF domain, GdpP, are present in the sequenced staphylococcal genomes. Here, we investigated the role of GdpS in biofilm formation in Staphylococcus epidermidis. Inactivation of gdpS impaired biofilm formation in medium supplemented with NaCl under static and flow-cell conditions, whereas gdpS overexpression complemented the mutation and enhanced wild-type biofilm development. GdpS increased production of the icaADBC-encoded exopolysaccharide, poly-N-acetyl-glucosamine, by elevating icaADBC mRNA levels. Unexpectedly, c-di-GMP synthesis was found to be irrelevant for the ability of GdpS to elevate icaADBC expression. Mutagenesis of the GGEEF motif essential for diguanylate cyclase activity did not impair GdpS, and the N-terminal fragment of GdpS lacking the GGDEF domain partially complemented the gdpS mutation. Furthermore, heterologous diguanylate cyclases expressed in trans failed to complement the gdpS mutation, and the purified GGDEF domain from GdpS possessed no diguanylate cyclase activity in vitro. The gdpS gene from Staphylococcus aureus exhibited similar characteristics to its S. epidermidis ortholog, suggesting that the GdpS-mediated signal transduction is conserved in staphylococci. Therefore, GdpS affects biofilm formation through a novel c-di-GMP-independent mechanism involving increased icaADBC mRNA levels and exopolysaccharide biosynthesis. Our data raise the possibility that staphylococci cannot synthesize c-di-GMP and have only remnants of a c-di-GMP signaling pathway.

更新日期：2019-11-01

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