Abstract
As important plant growth-promoting rhizobacteria, phosphate-solubilizing bacteria (PSB) fix nitrogen, dissolve potassium, promote growth, improve the soil micro-environment, and enhance soil fertility. A high-efficiency PSB strain from the pine tree rhizosphere, Burkholderia multivorans WS-FJ9, was screened in our laboratory. In this study, using a Bio Screener fully automatic microbial growth curve meter to determine the growth of the WS-FJ9 strain in phosphate-removing medium, the growth and mineral phosphate solubilization of WS-FJ9 were measured by Mo-Sb colorimetry and organophosphate-solubilization plate assays. Second-generation sequencing technology was used to obtain genomic information and to analyze possible phosphate decomposition genes. The related expression levels of these genes under different soluble phosphate levels were determined by quantitative real-time PCR. The results showed that WS-FJ9 had strong adaptability and capacity for mineral phosphate solubilization at low soluble phosphate levels, which is characterized by its low soluble phosphate induction and high soluble phosphate inhibition. The amount of solubilized mineral phosphate could exceed 140 mg/L. The total length of the WS-FJ9 genome was 7,497,552 bp after splicing, and the GC content was 67.37%. Eight phosphate-related genes were selected to determine their expression patterns at different soluble phosphate levels. Among them, AP-2, GspE and GspF were only related to organic phosphate, HlyB was only related to inorganic phosphate, and PhoR, PhoA, AP-1 and AP-3 were related to both. The WS-FJ9 strain utilizes multiple pathways for mineral phosphate solubilization, and the solubilization processes of different phosphate sources are interrelated and independent, indicating that the WS-FJ9 strain can adapt to different phosphate source environments and has good potential for future applications.
Highlights
Phosphorus (P) is an essential nutrient element for plant growth and development
Detection of phosphate‐solubilizing capacity of Burkholderia multivorans WS‐FJ9 The phosphate solubilization by strain WS-FJ9 on a phosphate-solubilizing plate is shown in Fig. 2: with the increase in the soluble phosphate concentration, the diameter of WS-FJ9 colonies increased, while the diameter of the transparent area decreased
The growth of strain WS-FJ9 was consistent with the growth in Fig. 1, which indicated that the growth rate of strain WS-FJ9 was not faster with a higher soluble phosphate content in the medium
Summary
Phosphorus (P) is an essential nutrient element for plant growth and development. P participates in most plant metabolic processes and is one of the factors that limits crop yield. It has been reported that 74% of the cultivated land in China lacks phosphate; 95% of the phosphorus. Improving the utilization rate of soil insoluble phosphate has become the primary limitation in agricultural and forestry development. Phosphate-solubilizing bacteria (PSB) in the rhizosphere have attracted increasing attention because of their advantages, such as environmental protection, low cost, and high efficiency (Khan et al 2007; Owen et al 2015). It is generally believed that PSB can dissolve insoluble inorganic phosphates by secretion of small molecule organic acids, proton exchange, and complexation and can degrade organic phosphate by secretion of solubilization enzymes, such as phosphatases and proteases (Qin et al 2019)
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