Phosphate-Solubilizing Bacterium Acinetobacter pittii gp-1 Affects Rhizosphere Bacterial Community to Alleviate Soil Phosphorus Limitation for Growth of Soybean (Glycine max)

Abstract

Phosphorus (P) availability is a major restriction to crop production, and phosphate-solubilizing bacteria (PSBs) in soils are responsible for P turnover. However, it remains unknown whether the application of PSB can facilitate both inorganic and organic P transformation and enhance function of plant rhizosphere bacteria. In this study, we applied Illumina MiSeq sequencing, plate-colony counting, quantitative PCR, and multiple ecological analyses. We found that the inoculation of PSB Acinetobacter pittii gp-1 significantly promoted the growth of soybean represented by better vegetation properties (e.g., plant height and root P) and increased activities of phosphatase (4.20–9.72 μg/g/h) and phytase (0.69–1.53 μmol/g/day) as well as content of indole acetic acid (5.80–40.35 μg/g/h). Additionally, the application of strain A. pittii gp-1 significantly increased abundances of both inorganic and organic P-cycling-related genes (i.e., phoD, bpp, gcd, and pstS). More importantly, the application of A. pittii gp-1 could increase the function represented by P-cycling-related enzymes (e.g., phosphotransferase) of rhizosphere bacterial community based on functional profiling. To our knowledge, this is the first report that the application of PSB A. pittii promotes inorganic and organic P utilization and increases the function of rhizosphere bacterial community. Therefore, the PSB A. pittii gp-1 could be a good candidate for the promotion of soybean growth.

Distribution of Culturable Phosphate-Solubilizing Bacteria in Soil Aggregates and Their Potential for Phosphorus Acquisition

“…strain Ac-14 for Arabidopsis thaliana ( 57 ), and Pseudomonas monteilii PsF84 for geranium ( 58 ). The inoculation of PSB can alter community function of soybean rhizosphere bacteria and increase P-cycling-related gene abundance and thus enhance vegetation properties ( 24 ). Previous reports have also reported that inorganic phosphate-solubilizing bacteria can release oxalic, lactic, malic, citric, succinic, and indole-3-acetic acid to enrich soluble P levels ( 9 , 23 , 53 , 57 ).…”

“…We evaluated the number of PSB using the colony plate counting method ( 24 ). Each soil aggregate (1 g) was added to 10 mL of sterile water.…”

“…The experimental potted soils were collected from an uncultivated field in Wuhan, China (30°28′N, 114°21′E). The original physicochemical properties and processing of experimental potted soils were described previously ( 24 ). Two potted treatments were designed: 1,000 g of sieved soil plus 500 mL of sterile water plus 100 NBRIP medium (CK group) and 1,000 g of sieved soil plus 500 mL of sterile water plus 90 mL NBRIP medium plus 10 mL bacterial suspension (PSB incubated at NBRIP for 3 days; 10 7 CFU/mL) (Exp group).…”

“…Each treatment had five replicates. Chinese cabbage (Shanghai Qing) seeds were purchased from China National Seed Group, precultivated in sterile nutritious soils, and allowed to grow to about 10-cm length of sprouts ( 24 ). Each sprout with the same growth potential was transplanted to each pot as described above, and a bacterial suspension containing PSB-2 was inoculated into cabbage rhizosphere.…”

“…Earlier studies have reported that tricalcium phosphate-solubilizing bacteria and phytate-degrading bacteria can promote plant growth via enhancing soil availability P ( 17 – 20 ). Recent studies have reported that PSB mainly belongs to Gram-negative bacteria (e.g., Acinetobacter , Citrobacter , Massilia , and Pseudomonas ) ( 3 , 21 – 24 ), whereas some are Gram-positive bacteria (e.g., Bacillus ) ( 17 ). For instance, Bacillus subtilis strain KPS-11 can produce indole-3-acetic acid and extracellular phytase, which in turn significantly promotes vegetation properties including height, fresh weight, and dry weight of potato ( Solanum tuberosum L.) ( 17 ).…”