Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA.
Department of Microbiology and Molecular Genetics, University of Pittsburghgrid.21925.3d, Pittsburgh, Pennsylvania, USA.
Appl Environ Microbiol. 2021 Oct 28;87(22):e0130621. doi: 10.1128/AEM.01306-21. Epub 2021 Sep 8.
Bacteria rapidly adapt to their environment by integrating external stimuli through diverse signal transduction systems. Pseudomonas aeruginosa, for example, senses surface contact through the Wsp signal transduction system to trigger the production of cyclic di-GMP. Diverse mutations in genes that manifest enhanced biofilm formation are frequently reported in clinical isolates of P. aeruginosa and in biofilm studies of Pseudomonas spp. and Burkholderia cenocepacia. In contrast to the convergent phenotypes associated with comparable mutations, we demonstrate that the Wsp system in B. cenocepacia does not impact intracellular cyclic di-GMP levels, unlike that in Pseudomonas spp. Our current mechanistic understanding of the Wsp system is based entirely on the study of four Pseudomonas spp., and its phylogenetic distribution remains unknown. Here, we present a broad phylogenetic analysis to show that the Wsp system originated in the betaproteobacteria and then horizontally transferred to Pseudomonas spp., the sole member of the gammaproteobacteria. Alignment of 794 independent Wsp systems with reported mutations from the literature identified key amino acid residues that fall within and outside annotated functional domains. Specific residues that are highly conserved but uniquely modified in B. cenocepacia likely define mechanistic differences among Wsp systems. We also find the greatest sequence variation in the extracellular sensory domain of WspA, indicating potential adaptations to diverse external stimuli beyond surface contact sensing. This study emphasizes the need to better understand the breadth of functional diversity of the Wsp system as a major regulator of bacterial adaptation beyond B. cenocepacia and select Pseudomonas spp. The Wsp signal transduction system serves as an important model system for studying how bacteria adapt to living in densely structured communities known as biofilms. Biofilms frequently cause chronic infections and environmental fouling, and they are very difficult to eradicate. In Pseudomonas aeruginosa, the Wsp system senses contact with a surface, which in turn activates specific genes that promote biofilm formation. We demonstrate that the Wsp system in Burkholderia cenocepacia regulates biofilm formation uniquely from that in Pseudomonas species. Furthermore, a broad phylogenetic analysis reveals the presence of the Wsp system in diverse bacterial species, and sequence analyses of 794 independent systems suggest that the core signaling components function similarly but with key differences that may alter what or how they sense. This study shows that Wsp systems are highly conserved and more broadly distributed than previously thought, and their unique differences likely reflect adaptations to distinct environments.
细菌通过多种信号转导系统整合外部刺激来快速适应其环境。例如,铜绿假单胞菌通过 Wsp 信号转导系统感知表面接触,从而触发环二鸟苷酸 (cyclic di-GMP) 的产生。在铜绿假单胞菌的临床分离株和假单胞菌属和洋葱伯克霍尔德菌的生物膜研究中,经常报道基因中的多种突变表现出增强的生物膜形成。与具有可比突变的趋同表型相反,我们证明与假单胞菌属不同,洋葱伯克霍尔德菌的 Wsp 系统不会影响细胞内环二鸟苷酸 (cyclic di-GMP) 水平。我们目前对 Wsp 系统的机制理解完全基于对四种假单胞菌的研究,其系统的系统发育分布仍然未知。在这里,我们进行了广泛的系统发育分析,表明 Wsp 系统起源于β变形菌,然后水平转移到假单胞菌属,这是γ变形菌的唯一成员。与文献中报道的突变相关的 794 个独立 Wsp 系统的比对,确定了关键的氨基酸残基,这些残基位于注释功能域内和外。在洋葱伯克霍尔德菌中高度保守但独特修饰的特定残基可能定义了 Wsp 系统之间的机制差异。我们还发现 WspA 细胞外感应结构域的序列变异最大,表明其可能适应除表面接触感应之外的多种外部刺激。这项研究强调需要更好地理解 Wsp 系统的功能多样性,因为它是细菌适应除洋葱伯克霍尔德菌和选择假单胞菌属以外的生物膜等密集结构群落的主要调节剂。Wsp 信号转导系统是研究细菌如何适应生活在称为生物膜的密集结构群落中的重要模型系统。生物膜经常导致慢性感染和环境污染,而且很难根除。在铜绿假单胞菌中,Wsp 系统感知与表面的接触,进而激活促进生物膜形成的特定基因。我们证明,洋葱伯克霍尔德菌中的 Wsp 系统在调节生物膜形成方面与假单胞菌属中的系统独特不同。此外,广泛的系统发育分析揭示了 Wsp 系统存在于多种细菌物种中,对 794 个独立系统的序列分析表明,核心信号成分的功能相似,但关键差异可能改变它们感知的内容或方式。这项研究表明,Wsp 系统比以前认为的更保守和广泛分布,它们的独特差异可能反映了对不同环境的适应。
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