PDF(Pubmed)
Abstract：
Swarming motility in pseudomonads typically requires both a functional flagellum and the production/secretion of a biosurfactant. Published work has shown that the wild-type Pseudomonas fluorescens Pf0-1 is swarming deficient due to a point mutation in the gacA gene, which until recently was thought to inactivate rather than attenuate the Gac/Rsm pathway. As a result, little is known about the underlying mechanisms that regulate swarming motility by P. fluorescens Pf0-1. Here, we demonstrate that a ΔrsmA ΔrsmE ΔrsmI mutant, which phenotypically mimics Gac/Rsm pathway overstimulation, is proficient at swarming motility. RsmA and RsmE appear to play a key role in this regulation. Transposon mutagenesis of the ΔrsmA ΔrsmE ΔrsmI mutant identified multiple factors that impact swarming motility, including pathways involved in flagellar synthesis and biosurfactant production/secretion. We find that loss of genes linked to biosurfactant Gacamide A biosynthesis or secretion impacts swarming motility, as does loss of the alternative sigma factor FliA, which results in a defect in flagellar function. Collectively, these findings provide evidence that P. fluorescens Pf0-1 can swarm if the Gac/Rsm pathway is activated, highlight the regulatory complexity of swarming motility in this strain, and demonstrate that the cyclic lipopeptide Gacamide A is utilized as a biosurfactant for swarming motility.IMPORTANCESwarming motility is a coordinated process that allows communities of bacteria to collectively move across a surface. For P. fluorescens Pf0-1, this phenotype is notably absent in the parental strain, and to date, little is known about the regulation of swarming in this strain. Here, we identify RsmA and RsmE as key repressors of swarming motility via modulating the levels of biosurfactant production/secretion. Using transposon mutagenesis and subsequent genetic analyses, we further identify potential regulatory mechanisms of swarming motility and link Gacamide A biosynthesis and transport machinery to swarming motility.
摘要：
假单胞菌中的群集运动通常需要功能性鞭毛和生物表面活性剂的产生/分泌。已发表的工作表明，由于gacA基因的点突变，野生型荧光假单胞菌Pf0-1成群缺乏，直到最近才被认为失活而不是减弱Gac/Rsm途径。因此,关于荧光假单胞菌Pf0-1调节蜂群运动的潜在机制知之甚少。这里,我们证明了一个ΔrsmaΔrsmEΔrsmI突变体，在表型上模拟Gac/Rsm通路过度刺激，精通蜂群运动。RsmA和RsmE似乎在该调节中起关键作用。ΔrsmAΔrsmEΔrsmI突变体的转座子诱变鉴定了影响成群运动的多种因素，包括参与鞭毛合成和生物表面活性剂生产/分泌的途径。我们发现与生物表面活性剂GacamideA生物合成或分泌相关的基因丢失会影响蜂群运动，替代西格玛因子FliA的损失也是如此，导致鞭毛功能缺陷。总的来说，这些发现提供了证据表明，如果Gac/Rsm通路被激活，荧光假单胞菌Pf0-1可以蜂群，突出了这种菌株群动的调节复杂性，并证明环状脂肽GacamideA被用作用于成群运动的生物表面活性剂。重要的变暖运动是一个协调的过程，允许细菌群落集体在表面上移动。对于荧光假单胞菌Pf0-1，该表型在亲本菌株中明显不存在，到目前为止，对这种菌株的蜂群调节知之甚少。这里,我们通过调节生物表面活性剂的产生/分泌水平，将RsmA和RsmE确定为成群运动的关键阻遏物。使用转座子诱变和随后的遗传分析，我们进一步确定了成群运动的潜在调节机制，并将GacamideA生物合成和运输机械与成群运动联系起来。
