Corporación Colombiana de Investigación Agropecuaria (AGROSAVIA), Mosquera, Colombia. Km 14 Bogotá-Mosquera, Mosquera, Colombia.
WG Fermentation and Formulation of Biologicals and Chemicals, Department of Engineering Sciences and Mathematics, Bielefeld University of Applied Sciences, Bielefeld, Germany.
World J Microbiol Biotechnol. 2019 Dec 12;36(1):6. doi: 10.1007/s11274-019-2780-0.
This study presents an anhydrobiotic engineering approach aiming at conferring a high degree of desiccation tolerance to the Gram-negative endophyte Kosakonia radicincitans. In particular, pre-conditioning of bacteria under high salinities provides a remarkable positive influence on drying survival. The endophytic bacteria accumulate exogenous hydroxyectoine > 500 µmol g dry weight cells exerted by osmotic stress at 4% NaCl. Microfermentation research demonstrated that hydroxyectoine provides positive effects on reducing the lag phase duration and alleviates the dissolved oxygen consumption under high salinity conditions. Beyond the amassing of hydroxyectoine, this work provides evidence supporting the notion that hydroxyectoine can produce significant changes in the endogenous bacterial metabolome during the exponential growth phase at high-osmolarity. Metabolome changes include alterations on tricarboxylic acid cycle, novo-synthesis of specific intracellular metabolites such as mannitol, myo-inositol and trehalose, and fold changes on amino acids such as L-leucine, L-asparagine, L-serine, L-methionine and L-proline. The significant fold change of L-aspartate suggests a potential acidic proteome at high-osmolarity environments, extending the knowledge of salt-stressed bacterial endophytes. Thus, these findings place the metabolic salt stress response and the hydroxyectoine accumulation by K. radicincitans into a physiological context, paving the way into the interaction between cellular phenotype associated with salt stress tolerance and drying survival capacity of Gram-negative endophytes.
本研究提出了一种抗干燥工程方法，旨在使革兰氏阴性内生菌 Kosakonia radicincitans 具有高度的干燥耐受性。特别是，在高盐度下对细菌进行预处理对干燥生存有显著的积极影响。内生细菌在 4%的 NaCl 下积累了 500 µmol g 干重细胞的外源羟基乙四醇来应对渗透压胁迫。微发酵研究表明，羟基乙四醇对减少高盐条件下的延迟期和缓解溶解氧消耗具有积极作用。除了积累羟基乙四醇外，本工作还提供了证据支持羟基乙四醇可以在高渗透压指数增长阶段引起内源性细菌代谢组发生显著变化的观点。代谢组变化包括三羧酸循环的改变、新型特定细胞内代谢物（如甘露醇、肌醇和海藻糖）的合成，以及氨基酸（如 L-亮氨酸、L-天冬酰胺、L-丝氨酸、L-甲硫氨酸和 L-脯氨酸）的倍数变化。L-天冬氨酸的显著倍数变化表明在高渗透压环境中存在潜在的酸性蛋白质组，扩展了对盐胁迫细菌内生菌的了解。因此，这些发现将代谢盐胁迫反应和 K. radicincitans 中羟基乙四醇的积累置于生理背景下，为与盐胁迫耐受性和革兰氏阴性内生菌干燥生存能力相关的细胞表型之间的相互作用铺平了道路。
