Augimeri Richard V, Strap Janice L
Molecular Microbial Biochemistry Laboratory, Faculty of Science, University of Ontario Institute of Technology, Oshawa ON, Canada.
Front Microbiol. 2015 Dec 22;6:1459. doi: 10.3389/fmicb.2015.01459. eCollection 2015.
Komagataeibacter (formerly Gluconacetobacter) xylinus ATCC 53582 is a plant-associated model organism for bacterial cellulose (BC) biosynthesis. This bacterium inhabits the carposphere where it interacts with fruit through the bi-directional transfer of phytohormones. The majority of research regarding K. xylinus has been focused on identifying and characterizing structural and regulatory factors that control BC biosynthesis, but its ecophysiology has been generally overlooked. Ethylene is a phytohormone that regulates plant development in a variety of ways, but is most commonly known for its positive role on fruit ripening. In this study, we utilized ethephon (2-chloroethylphosphonic acid) to produce in situ ethylene to investigate the effects of this phytohormone on BC production and the expression of genes known to be involved in K. xylinus BC biosynthesis (bcsA, bcsB, bcsC, bcsD, cmcAx, ccpAx and bglAx). Using pellicle assays and reverse transcription quantitative polymerase chain reaction (RT-qPCR), we demonstrate that ethephon-derived ethylene enhances BC directly in K. xylinus by up-regulating the expression of bcsA and bcsB, and indirectly though the up-regulation of cmcAx, ccpAx, and bglAx. We confirm that IAA directly decreases BC biosynthesis by showing that IAA down-regulates bcsA expression. Similarly, we confirm that ABA indirectly influences BC biosynthesis by showing it does not affect the expression of bcs operon genes. In addition, we are the first to report the ethylene and indole-3-acetic acid (IAA) induced differential expression of genes within the bacterial cellulose synthesis (bcs) operon. Using bioinformatics we have identified a novel phytohormone-regulated CRP/FNRKx transcription factor and provide evidence that it influences BC biosynthesis in K. xylinus. Lastly, utilizing current and previous data, we propose a model for the phytohormone-mediated fruit-bacteria interactions that K. xylinus experiences in nature.
木醋杆菌（以前称为葡糖醋杆菌）木糖氧化亚种ATCC 53582是用于细菌纤维素（BC）生物合成的植物相关模式生物。这种细菌栖息在果实表面，通过植物激素的双向转移与果实相互作用。关于木醋杆菌的大多数研究都集中在鉴定和表征控制BC生物合成的结构和调节因子上，但其生态生理学通常被忽视。乙烯是一种以多种方式调节植物发育的植物激素，但最广为人知的是其在果实成熟中的积极作用。在本研究中，我们利用乙烯利（2-氯乙基膦酸）原位产生乙烯，以研究这种植物激素对BC产量以及已知参与木醋杆菌BC生物合成的基因（bcsA、bcsB、bcsC、bcsD、cmcAx、ccpAx和bglAx）表达的影响。通过菌膜测定和逆转录定量聚合酶链反应（RT-qPCR），我们证明乙烯利衍生的乙烯通过上调bcsA和bcsB的表达直接增强木醋杆菌中的BC，并通过上调cmcAx、ccpAx和bglAx间接增强。我们通过显示IAA下调bcsA表达来证实IAA直接降低BC生物合成。同样，我们通过显示ABA不影响bcs操纵子基因的表达来证实ABA间接影响BC生物合成。此外，我们首次报道了乙烯和吲哚-3-乙酸（IAA）诱导细菌纤维素合成（bcs）操纵子内基因的差异表达。利用生物信息学，我们鉴定了一种新型的植物激素调节的CRP/FNRKx转录因子，并提供证据表明它影响木醋杆菌中的BC生物合成。最后，利用当前和以前的数据，我们提出了一个木醋杆菌在自然界中经历的植物激素介导的果实-细菌相互作用模型。
