Elucidating the effect of biofertilizers on bacterial diversity in maize rhizosphere soil.

Junhong Wang,Mengliang Wang,Xiaoyin Gao,Jianxia Hao,Lei Liu,Muhammad Shahid

doi:10.1371/journal.pone.0249834

Abstract

This study was conducted to investigate the effect of biofertilizers on the structure and diversity of the rhizosphere bacterial community of maize. Different biofertilizers were applied to maize. The physical and chemical properties of rhizosphere soil samples were analyzed and the rhizosphere bacteria were analyzed by 16S amplicon sequencing. The results showed that treatment with Bacillus licheniformis and B. amyloliquefaciens as biofertilizers increased the soil organic matter (SOM), total nitrogen, total phosphorus (TP), available phosphorus (AP), and available potassium (AK) contents, indicating that the plant growth-promoting rhizobacteria in the biofertilizers might help the host plant to produce root exudates that, in return, recruit beneficial communities due to available sugars, amino acids, organic acids, vitamins, and polymers. The rhizosphere of maize treated with B. subtilis biofertilizer had the highest diversity and richness. However, the rhizosphere treated with the combined bacterial strains had the lowest diversity and richness, which might be due to the directional increase of the abundance of some bacteria with special functions, but the decrease of the overall bacterial community diversity in the soil. The dominant bacterial phyla were Proteobacteria (32.2%–34.6%), Acidobacteria (15.0%–21.0%), Actinobacteria (13.1%–17.2%), and Gemmatimonadetes (9.0%–10.8%), and the dominant bacterial species were Aciditerrimonas ferrireducens JCM 15389 (4.3%–5.2%), Gemmatimonas aurantiaca (3.2%–4.1%), and Pyrinomonas methylaliphatogenes (2.1%–4.8%). The significantly enriched bacterial functions were associated with amino acid metabolism, sugar metabolism, and energy metabolism pathways. The results of a redundancy analysis showed that SOM, TP, and AK were the main factors affecting the microbial community structure in the maize rhizosphere. In conclusion, the application of biofertilizers increased the diversity and richness of the bacterial community in the maize rhizosphere soil. However, combined strain treatment was failed and not an ideal strategy due to the lowest abundance and diversity.

Highlights

The rhizosphere is a narrow soil zone surrounding plant roots that is inhabited by numerous microorganisms
The corn variety used in the test was Qiangsheng 388, which was selected by Shanxi Academy of Agricultural Sciences for corn research; the test fertilizer used was “Stanley” slow release blending fertilizer (N:P2O5:K2O = 26:12:10); and the test strains used as biofertilizers were B. subtilis, B. licheniformis, and B. amyloliquefaciens, which were provided by the Biochemical Laboratory of Institute of Applied Chemistry, Shanxi University
The control group was only treated with fertilizer; the B. subtilis group was treated with fertilizer + biofertilizer containing B. subtilis; the B. licheniformis group was treated with fertilizer + biofertilizer containing B. licheniformis; the B. amyloliquefaciens group was treated with fertilizer + biofertilizer containing B. amyloliquefaciens; and the combined strains group was treated with fertilizer + biofertilizer containing a mixture of all three Bacillus strains in equal proportions (33.3% each)

Summary

Introduction

The rhizosphere is a narrow soil zone surrounding plant roots that is inhabited by numerous microorganisms. The extensive use of chemical fertilizers, especially nitrogen fertilizers, has reduced soil nutrient availability and led to environmental degradation [11] and imbalances in the soil and microbial community structure, all of which may affect crop yields [12]. Related studies have indicated that both inorganic and organic fertilizers can change the composition of soil bacterial communities by altering the physical and chemical properties of the soil or by altering the carbon input of surface and underground plant residues [18,19,20]. We investigated whether different biofertilizers containing Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, or a combination of these Bacillus strains could affect the physical and chemical properties and bacterial composition of maize rhizosphere soil. We hypothesized that the application of biofertilizers could increase the diversity and richness of the bacterial community in maize rhizosphere soil

Materials and methods

Results

Discussion