Faculty of Agricultural, Environmental and Food Sciences, Free University of Bolzano, Piazza Università 5, Bolzano, 39100, Italy.
Department of Biochemistry and Biotechnology, State University of Londrina, Londrina, Paraná, Brazil.
BMC Microbiol. 2023 Jul 12;23(1):184. doi: 10.1186/s12866-023-02918-6.
The release of organic acids (OAs) is considered the main mechanism used by phosphate-solubilizing bacteria (PSB) to dissolve inorganic phosphate in soil. Nevertheless, little is known about the effect of individual OAs produced by a particular PSB in a soil-plant system. For these reasons, the present work aimed at investigating the effect of Enterobacter sp. strain 15S and the exogenous application of its OAs on (i) the solubilization of tricalcium phosphate (TCP), (ii) plant growth and (iii) P nutrition of cucumber. To this purpose two independent experiments have been performed.
In the first experiment, carried out in vitro, the phosphate solubilizing activity of Enterobacter 15S was associated with the release of citric, fumaric, ketoglutaric, malic, and oxalic acids. In the second experiment, cucumber plants were grown in a Leonard jar system consisting of a nutrient solution supplemented with the OAs previously identified in Enterobacter 15S (jar's base) and a substrate supplemented with the insoluble TCP where cucumber plants were grown (jar's top). The use of Enterobacter 15S and its secreted OAs proved to be efficient in the in situ TCP solubilization. In particular, the enhancement of the morpho-physiological traits of P-starved cucumber plants was evident when treated with Enterobacter 15S, oxalate, or citrate. The highest accumulation of P in roots and shoots induced by such treatments further corroborated this hypothesis.
In our study, the results presented suggest that organic acids released by Enterobacter 15S as well as the bacterium itself can enhance the P-acquisition by cucumber plants.
有机酸（OAs）的释放被认为是解磷菌（PSB）溶解土壤中无机磷的主要机制。然而，对于特定 PSB 在土壤-植物系统中产生的个别 OAs 的影响知之甚少。出于这些原因，本工作旨在研究肠杆菌属 15S 菌株及其 OAs 的外源应用对（i）磷酸三钙（TCP）的溶解、（ii）植物生长和（iii）黄瓜的磷营养的影响。为此进行了两项独立的实验。
在体外进行的第一项实验中，肠杆菌 15S 的溶磷活性与柠檬酸、富马酸、酮戊二酸、苹果酸和草酸的释放有关。在第二项实验中，黄瓜植物在伦纳德罐系统中生长，该系统由补充了先前在肠杆菌 15S 中鉴定出的 OAs 的营养液（罐底）和补充了不溶性 TCP 的基质（罐顶）组成，黄瓜植物在基质中生长。使用肠杆菌 15S 及其分泌的 OAs 被证明在原位 TCP 溶解中是有效的。特别是，当用肠杆菌 15S、草酸盐或柠檬酸盐处理时，缺磷黄瓜植物的形态生理特性得到明显增强。这种处理诱导的根和地上部 P 积累最高进一步证实了这一假设。
在我们的研究中，所呈现的结果表明，肠杆菌 15S 释放的有机酸以及该细菌本身可以增强黄瓜植物对 P 的获取。
