Department of Plant and Microbial Biology, University of Zurich, Zürich, Switzerland.
Department of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
J Bacteriol. 2020 Nov 4;202(23). doi: 10.1128/JB.00304-20.
is a soil saprophyte that is closely related to the pathogen , the etiological agent of melioidosis in humans. The environmental niches and infection sites occupied by these bacteria are thought to contain only limited concentrations of oxygen, where they can generate energy via denitrification. However, knowledge of the underlying molecular basis of the denitrification pathway in these bacteria is scarce. In this study, we employed a transposon sequencing (Tn-Seq) approach to identify genes conferring a fitness benefit for anaerobic growth of Of the 180 determinants identified, several genes were shown to be required for growth under denitrifying conditions: the nitrate reductase operon , the gene encoding a previously unknown nitrite reductase, and the genes encoding a cytochrome , as well as three novel regulators that control denitrification. Our Tn-Seq data allowed us to reconstruct the entire denitrification pathway of and shed light on its regulation. Analyses of growth behaviors combined with measurements of denitrification metabolites of various mutants revealed that nitrate reduction provides sufficient energy for anaerobic growth, an important finding in light of the fact that some pathogenic species can use nitrate as a terminal electron acceptor but are unable to complete denitrification. Finally, we demonstrated that a nitrous oxide reductase mutant is not affected for anaerobic growth but is defective in biofilm formation and accumulates NO, which may play a role in the dispersal of biofilms. is a soil-dwelling saprophyte that is often used as surrogate of the closely related pathogen , the causative agent of melioidosis and a classified biowarfare agent. Both organisms are adapted to grow under oxygen-limited conditions in rice fields by generating energy through denitrification. Microoxic growth of is also considered essential for human infections. Here, we have used a Tn-Seq approach to identify the genes encoding the enzymes and regulators required for growth under denitrifying conditions. We show that a mutant that is defective in the conversion of NO to N, the last step in the denitrification process, is unaffected in microoxic growth but is severely impaired in biofilm formation, suggesting that NO may play a role in biofilm dispersal. Our study identified novel targets for the development of therapeutic agents to treat meliodiosis.
是一种土壤腐生菌，与人类病原体（导致类鼻疽病的病原体）密切相关。这些细菌的生态位和感染部位被认为只含有有限浓度的氧气，它们可以通过反硝化作用产生能量。然而，对于这些细菌中反硝化途径的潜在分子基础的了解还很有限。在这项研究中，我们采用转座子测序（Tn-Seq）方法来鉴定赋予厌氧生长优势的基因。在鉴定的 180 个决定因素中，有几个基因被证明是在反硝化条件下生长所必需的：硝酸盐还原酶操纵子、编码一种以前未知的亚硝酸盐还原酶的 基因、编码细胞色素的 基因，以及三个控制反硝化的新调节因子。我们的 Tn-Seq 数据使我们能够重建 完整的反硝化途径，并揭示其调控机制。对生长行为的分析结合对各种突变体的硝酸盐还原代谢物的测量表明，硝酸盐还原为厌氧生长提供了足够的能量，这一发现很重要，因为一些致病 物种可以将硝酸盐作为末端电子受体，但不能完成反硝化作用。最后，我们证明了一氧化二氮还原酶突变体不会影响厌氧生长，但在生物膜形成方面存在缺陷，并积累了 NO，这可能在 生物膜的分散中起作用。是一种土壤栖息的腐生菌，常被用作密切相关病原体的替代品，该病原体是类鼻疽病的病原体，也是一种分类生物战剂。这两种生物都通过反硝化作用产生能量来适应在稻田中生长在有限的氧气条件下。 的微氧生长也被认为对人类感染至关重要。在这里，我们使用 Tn-Seq 方法来鉴定生长在反硝化条件下所需的酶和调节因子的编码基因。我们表明，在反硝化过程的最后一步将 NO 转化为 N 的突变体在微氧生长中不受影响，但在生物膜形成中严重受损，这表明 NO 可能在生物膜分散中起作用。我们的研究确定了治疗类鼻疽病的治疗药物开发的新靶点。
