The RNA chaperone, Hfq, is a global post-transcriptional regulator that plays an important role in regulating pleiotropic functions, such as cell growth and motility, stress tolerance, and virulence to host, in many Gram-negative bacteria. This study examined the functional roles of Hfq in Rahnella aquatilis HX2, a plant beneficial, selenium nanoparticles (SeNPs)-producing soil bacterium. A mutant HX2∆hfq with an in-frame deletion within the hfq gene in R. aquatilis HX2 was constructed and tested for various phenotypic features. Bacterial growth, motility, selenite reduction, and SeNPs production were compared between the mutant, the wild-type, and the complementation strain. The hfq gene deletion delayed the growth of strain HX2, with a lower bacterial population during the stationary phase, and significantly impaired the swimming motility of the bacterium, showing a smaller motility ring on the plate. The hfq mutation also dramatically declined microbial-induced reduction of selenite and SeNPs production in HX2, which was independent of cell growth. The introduction of a trans-expressed hfq gene into HX2∆hfq for complementation completely restored impacted phenotypes. In addition, reverse transcription real-time quantitative PCR (RT-qPCR) analysis revealed that the expression of ten genes involved in bacterial growth and survival, motility and chemotaxis, and selenite or seleno-compound metabolism were influenced by Hfq loss-of-function by at least two-fold. Six genes including two involved in SeNPs production were positively regulated by hfq, while other four genes were negatively regulated. Homolog search suggested that the rprA gene might encode a small RNA regulated by Hfq in R. aquatilis HX2. Overall, the present study provides novel information about the function of Hfq and the regulation of bacterial biosynthesis of SeNPs.

中文翻译：

---

小分子RNA分子伴侣Hfq是细菌纳米粒中细菌硒的生物合成和运动性的关键调节剂。

RNA伴侣Hfq是一种全球转录后调节剂，在许多革兰氏阴性细菌中，在调节多效性功能（例如细胞生长和运动性，应激耐受性以及对宿主的毒力）中起着重要作用。这项研究检查了Hfq在水生拉纳菌HX2（一种植物有益的产生硒纳米颗粒（SeNPs）的土壤细菌）中的功能作用。构建了一个突变型HX2Δhfq，该突变体在水生罗非鱼HX2的hfq基因内具有读框内缺失，并测试了各种表型特征。比较了突变体，野生型和互补菌株之间的细菌生长，运动性，亚硒酸盐的还原和SeNPs的产生。hfq基因缺失延迟了HX2菌株的生长，在稳定期细菌种群减少，并严重损害了细菌的游泳运动，在板上显示出较小的运动环。hfq突变还显着降低了微生物诱导的HX2中亚硒酸盐和SeNPs产量的减少，而这与细胞的生长无关。在HX2Δhfq中引入反式表达的hfq基因进行互补，可以完全恢复受影响的表型。此外，逆转录实时定量PCR（RT-qPCR）分析显示，涉及细菌生长和存活，运动性和趋化性以及亚硒酸盐或硒化合物代谢的十个基因的表达受Hfq功能丧失的影响至少两倍。hfq对6个基因（包括涉及SeNPs产生的2个基因）进行正调控，而对其他4个基因进行负调控。同源搜索表明rprA基因可能编码一个受Rfq调控的R. aquatilis HX2小RNA。总体而言，本研究提供了有关Hfq功能和SeNPs细菌生物合成调控的新信息。