Pseudomonas aeruginosa rugose small-colony variants (RSCVs) are frequently isolated from chronic infections, yet, they are rarely reported in environmental isolates. Here, during the comparative genomic analysis of two P. aeruginosa strains isolated from crude oil, we discovered a spontaneous in-frame deletion, wspA_Δ280–307, which led to hyper-biofilm and RSCV phenotypes. WspA is a homologue of methyl-accepting chemotaxis proteins (MCPs) that senses surfaces to regulate biofilm formation by stimulating cyclic-di-guanosine monophosphate (c-di-GMP) synthesis through the Wsp system. However, the methylation sites of WspA have never been identified. In this study, we identified E280 and E294 of WspA as methylation sites. The wspA_Δ280–307 mutation enabled the Wsp system to lock into a constitutively active state that is independent of regulation by methylation. The result is an enhanced production of c-di-GMP. Sequence alignment revealed three conserved repeat sequences within the amino acid residues 280–313 (aa280–313) region of WspA homologues, suggesting that a spontaneous deletion within this DNA encoding region was likely a result of intragenic recombination and that similar mutations might occur in several related bacterial genera. Our results provide a plausible explanation for the selection of RSCVs and a mechanism to confer a competitive advantage for P. aeruginosa in a crude-oil environment.

中文翻译：

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表面传感受体 WspA 的突变将 Wsp 信号转导系统锁定为组成型活跃状态

铜绿假单胞菌皱褶小菌落变体 (RSCV) 经常从慢性感染中分离出来，但在环境分离物中很少报道。在这里，在两个P的比较基因组分析中。从原油中分离出的铜绿假单胞菌菌株，我们发现了一个自发的框内缺失， wspA _Δ280-307，这导致了超生物膜和 RSCV 表型。WspA 是甲基接受趋化蛋白 (MCP) 的同系物，它通过 Wsp 系统刺激环状二鸟苷一磷酸 (c-di-GMP) 合成来感知表面以调节生物膜形成。然而，WspA 的甲基化位点从未被发现。在这项研究中，我们将 WspA 的 E280 和 E294 鉴定为甲基化位点。这wspA _Δ280-307突变使 Wsp 系统能够锁定到独立于甲基化调节的组成型活性状态。结果是提高了 c-di-GMP 的产量。序列比对揭示了 WspA 同源物的氨基酸残基 280-313 (aa280-313) 区域内的三个保守重复序列，表明该 DNA 编码区域内的自发缺失可能是基因内重组的结果，并且类似的突变可能发生在几个相关细菌属。我们的结果为 RSCV 的选择和赋予P竞争优势的机制提供了合理的解释。原油环境中的绿脓杆菌。