Secretion of Gluconic Acid From Nguyenibacter sp. L1 Is Responsible for Solubilization of Aluminum Phosphate

Abstract

Phosphorus (P) deficiency is one of the major factors limiting plant growth in acid soils, where most P is fixed by toxic aluminum (Al). Phosphate-solubilizing bacteria (PSBs) are important for the solubilization of fixed P in soils. Many PSBs have been isolated from neutral and calcareous soils, where calcium phosphate is the main P form, whereas PSBs in acid soils have received relatively little attention. In this study, we isolated a PSB strain from the rhizosphere of Lespedeza bicolor, a plant well adapted to acid soils. On the basis of its 16S rRNA gene sequence, this strain was identified as a Nguyenibacter species and named L1. After incubation of Nguyenibacter sp. L1 for 48 h in a culture medium containing AlPO4 as the sole P source, the concentration of available P increased from 10 to 225 mg L–1, and the pH decreased from 5.5 to 2.5. Nguyenibacter sp. L1 exhibited poor FePO4 solubilization ability. When the pH of non-PSB-inoculated medium was manually adjusted from 5.5 to 2.5, the concentration of available P only increased from 6 to 65 mg L–1, which indicates that growth medium acidification was not the main contributor to the solubilization of AlPO4 by Nguyenibacter sp. L1. In the presence of glucose, but not fructose, Nguyenibacter sp. L1 released large amounts of gluconic acid to solubilize AlPO4. Furthermore, external addition of gluconic acid enhanced AlPO4 solubilization and reduced Al toxicity to plants. We conclude that secretion of gluconic acid by Nguyenibacter sp. L1, which is dependent on glucose supply, is responsible for AlPO4 solubilization as well as the alleviation of Al phytotoxicity by this bacterial strain.

Effect of severe wildfire on soil phosphorus fractions and adsorption in a cold temperate coniferous forest after 5 years

“…A number of previous studies suggest that clay minerals may be important P-binding components in most soils and control the P adsorption capacity, which is inconsistent with this article, which may be due to the fact that there is no significant difference in the cohesive content of different tested soils (Figure 2) (Alovisi et al, 2020;Gérard, 2016;Li, Kang, et al, 2021;Li, Ni, et al, 2021;Li, Zhao, et al, 2021). Based on the results of correlation analysis, we speculate that the increase in Al d in topsoil after wildfires may be a key factor leading to the adsorption of IHP in the high-concentration stage (Table 4a) (Ahmed, Huang, et al, 2021;Ahmed, Jing, et al, 2021).…”

“…Soil organic carbon (SOC) content was determined by the dichromate wet oxidation method; SOM content was calculated by multiplying the values of the SOC by 1.724 (Sun et al, 2018). The determination methods of different forms of Fe/Al oxides in soil were as follows: free crystalline Fe/Al oxides (Fe d , Al d ) were extracted by the disulfite‐citrate‐bicarbonate (DCB) method, while amorphous Fe oxides (Fe ox ) were extracted by the acidic ammonium oxalate method, both of which were assayed by the colorimetric method (Li, Kang, et al, 2021; Li, Ni, et al, 2021; Li, Zhao, et al, 2021). Soil texture was determined by the sieve‐pipette method, SOM was removed by oxidation with hydrogen peroxide, in which soil aggregates were dispersed.…”

Distinct Patterns of Rhizosphere Microbiota Associated With Rice Genotypes Differing in Aluminum Tolerance in an Acid Sulfate Soil

“…In a recent study, we observed that Nguyenibacter sp. L1 isolated from the rhizosphere of the Altolerant plant Lespedeza bicolor solubilizes fixed P and alleviates the toxic effects of Al on rice by secreting organic acids (Li et al, 2021). The results of these analyses collectively suggest that the specific bacterial and fungal taxa enriched in the rhizosphere of Al-tolerant rice genotypes may potentially influence the secretion of organic acids by plants and P solubilization as well as promote plant growth, thereby modulating rice Al tolerance and P uptake efficiency.…”

The Plant-Rhizobial Symbiotic Interactions Provide Benefits to the Host beyond Nitrogen Fixation That Promote Plant Growth and Productivity

“…Although an external application of succinic acid inhibits P solubilization in legumes (e.g., chickpea) [71], several organic acids of microbial origin have been shown to participate in P solubilization in soil [70,72]. Gluconic acid is one of the P-solubilizing organic acids produced by root-associated rhizobia [63,68,73,74]. Its production by non-rhizobial bacteria including Azospirillum and Nguyenibacter is involved in the solubilization of calcium phosphate and aluminum phosphate [73,74].…”

“…Gluconic acid is one of the P-solubilizing organic acids produced by root-associated rhizobia [63,68,73,74]. Its production by non-rhizobial bacteria including Azospirillum and Nguyenibacter is involved in the solubilization of calcium phosphate and aluminum phosphate [73,74]. Besides gluconic acid, the solubilization of Ca and Fe phosphates could also be mediated through other organic acids [68,75].…”