Ge Gao,Yan Zhang,Shaofang Niu,Yu Chen,Shaojing Wang,Nusratgul Anwar,Shuai Chen,Guoqiang Li,Ting Ma
Precise classification of bacteria facilitates prediction of their ecological niche. The genusEnterobacterincludes pathogens of plants and animals but also beneficial bacteria that may require reclassification. Here, we propose reclassification ofEnterobacterFY-07 (FY-07), a strain that has many plant-growth-promoting traits and produces bacterial cellulose (BC), to theKosakoniagenera. To re-examine the taxonomic position of FY-07, a polyphasic approach including 16S rRNA gene sequence analysis, ATP synthase β subunit (atpD) gene sequence analysis, DNA gyrase (gyrB) gene sequence analysis, initiation translation factor 2 (infB) gene sequence analysis, RNA polymerase β subunit (rpoB) gene sequence analysis, determination of DNA G + C content, average nucleotide identity based on BLAST, in silico DNA–DNA hybridization and analysis of phenotypic features was applied. This polyphasic analysis suggested thatEnterobactersp. FY-07 should be reclassified asKosakonia oryzendophyticaFY-07. In addition, the potential of FY-07 to promote plant growth was also investigated by detecting related traits and the colonization of FY-07 in rice roots.Keywords:Enterobacter;Kosakonia;reclassification;FY-07;promote plant growth
Cyclic di-GMP (c-di-GMP) acts as a bacterial second messenger that regulates various physiological processes, including biofilm formation, motility, and virulence. It is synthesized by diguanylate cyclases (DGCs) and degraded by phosphodiesterases (PDEs), with precise regulatory effects typically requiring the coordinated action of multiple DGCs and PDEs. Kosakonia oryzendophytica FY-07 (FY-07) exhibits high bacterial cellulose (BC) yield, rapid growth, and robustness and can produce BC under varying oxygen conditions; however, the underlying mechanism driving the phenotypic transition from cellulose-producing to motile states during fermentation has yet to be elucidated. In this study, we aimed to identify two DGCs, KoBdcA and KoBdcB, and one PDE, KoBpdA, whose encoding genes are located adjacent to the cellulose synthesis operon in FY-07. KoBdcA and KoBpdA form an antagonistic DGC-PDE pair that maintains intracellular c-di-GMP homeostasis. Deletion of either gene alters BC production and motility. In contrast, KoBdcB acts as an auxiliary component, and its deletion alone causes no phenotypic changes. KoBdcA regulates BC synthesis via an indirect interaction with BcsA mediated by KoBdcB. The Per-Arnt-Sim (PAS) domains of KoBdcA and KoBpdA bind hemin, enabling them to sense oxygen and modulate their enzymatic activities. Elevated DGC activity during early fermentation promotes BC production, while increased PDE activity later suppresses BC synthesis, shifting cells to a motile state.
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