DiGianivittorio Pauline, Hinkel Lauren A, Mackinder Jacob R, Schutz Kristin, Klein Eric A, Wargo Matthew J
Department of Microbiology and Molecular Genetics, Larner College of Medicine, University of Vermont, Burlington, USA.
Cellular, Molecular, and Biomedical Sciences Graduate Program, University of Vermont, Burlington, USA.
Microbiology (Reading). 2025 Jan;171(1). doi: 10.1099/mic.0.001520.
Sphingoid bases, including sphingosine, are important components of the antimicrobial barrier at epithelial surfaces where they can cause growth inhibition and killing of susceptible bacteria. is a common opportunistic pathogen that is less susceptible to sphingosine than many Gram-negative bacteria. Here, we determined that the deletion of the operon reduced growth in the presence of sphingosine. Using deletion mutants, complementation and growth assays in PAO1, we determined that the and genes, encoding a periplasmic oxidase and periplasmic cytochrome c, respectively, were important for growth on sphingosine, while was dispensable under these conditions. Deletion of in PA14, Pf-5 and Pf01 also showed reduced growth in the presence of sphingosine. The genes were also important for growth in the presence of two other sphingoid bases, phytosphingosine and sphinganine. In WT , sphingosine is metabolized to an unknown non-inhibitory product, as sphingosine concentrations drop in the culture. However, in the absence of , sphingosine accumulates, pointing to SphC and SphB as having a role in sphingosine metabolism. Finally, the metabolism of sphingosine by WT protected susceptible cells from full growth inhibition by sphingosine, pointing to a role for sphingosine metabolism as a public good. This work shows that the metabolism of sphingosine by presents a novel pathway by which bacteria can alter host-derived sphingolipids, but it remains an open question whether SphB and SphC act directly on sphingosine.
鞘氨醇碱，包括鞘氨醇，是上皮表面抗菌屏障的重要组成部分，它们能抑制敏感细菌的生长并将其杀死。铜绿假单胞菌是一种常见的机会致病菌，与许多革兰氏阴性菌相比，它对鞘氨醇的敏感性较低。在此，我们确定删除鞘氨醇代谢操纵子会降低在鞘氨醇存在时的生长。通过在铜绿假单胞菌PAO1中使用缺失突变体、互补和生长试验，我们确定分别编码周质氧化酶和周质细胞色素c的sphC和sphB基因对于在鞘氨醇上生长很重要，而在这些条件下sphD是可有可无的。在铜绿假单胞菌PA14、恶臭假单胞菌Pf - 5和荧光假单胞菌Pf01中删除sphC也显示在鞘氨醇存在时生长减少。sphC和sphB基因对于在另外两种鞘氨醇碱植物鞘氨醇和二氢鞘氨醇存在时的生长也很重要。在野生型铜绿假单胞菌中，随着培养物中鞘氨醇浓度下降，鞘氨醇被代谢为一种未知的非抑制性产物。然而，在缺乏sphC时，鞘氨醇会积累，这表明SphC和SphB在鞘氨醇代谢中起作用。最后，野生型铜绿假单胞菌对鞘氨醇的代谢保护了敏感细胞免受鞘氨醇的完全生长抑制，这表明鞘氨醇代谢作为一种公共益品发挥了作用。这项工作表明铜绿假单胞菌对鞘氨醇的代谢呈现出一种细菌可以改变宿主来源鞘脂的新途径，但SphB和SphC是否直接作用于鞘氨醇仍是一个悬而未决的问题。
