Mechanisms for Solubilization of Various Insoluble Phosphates and Activation of Immobilized Phosphates in Different Soils by an Efficient and Salinity-Tolerant Aspergillus niger Strain An2

Abstract

Mechanisms for solubilization of different types of phosphates and activation of immobilized phosphates in different types of soils by an efficient fungal strain An2 were explored and evaluated in this study. An2 was isolated from a Chinese cabbage rhizosphere soil and identified as Aspergillus niger. It could fast release up to 1722, 2066, and 2356 mg L(-1) of soluble phosphorus (P) from 1 % Ca3(PO4)2, Mg3(PO4)2, and AlPO4 (Ca-P, Mg-P, and Al-P) and 215 and 179 mg L(-1) from 0.5 % FePO4 and rock phosphate (Fe-P and RP), respectively. HPLC assay demonstrated that An2 mainly secreted oxalic acid to solubilize Ca-P, Mg-P, Al-P, and Fe-P whereas secreted tartaric acid to solubilize RP. Furthermore, An2 could tolerate salinity up to 4 % NaCl without impairing its phosphate-solubilizing ability. The simulation experiments validated that An2 was able to effectively activate immobilized phosphates in general calcareous, acidic, as well as saline-alkali soils with high total P content. This study shows new insights into the mechanisms for microbial solubilization of different types of phosphates and supports the future application of strain An2 in different types of soils to effectively activate P for plants.

Effect of various microorganisms on phosphorus uptake from insoluble Ca‐phosphates by cucumber plants

“…Thus, LMWOA exudation may be a response to low P availability but not an effective mechanism for increasing P availability to plants under these conditions in agreement with Ström et al (2005). The present study does not provide evidence of a LMWOA‐mediated effect of P‐mobilizing microorganisms on P uptake by plants, which contradicts classical theories explaining the effects of some PGPR such as Bacillus on P plant nutrition ( Rodríguez and Fraga , 1999; Chen et al, 2006) or secretion of oxalic, succinic, and citric acids by A. niger during phosphate solubilization ( Khan et al, 2010; Li et al., 2015).…”

“…Substantial amounts of CFU were found in all experiments with plants irrespective of P source (data not shown). Therefore, the non‐significant differences of B. amyloliquefaciens strain FZB24, A. niger CBS513.88 and T34 with the control treatment (no inoculation) cannot be ascribed to deficient rhizosphere colonization and contradicts evidences observed for other strains [ e.g ., Li et al, 2015 ( A. niger ); Xu et al, 2015 ( B. amyloliquefaciens )]. T34 showed an intermediate P mobilizing ability in the siliceous medium (available P) and no effect in calcareous media.…”

“…Another common fungus, Aspergillus niger , has been recognized as one of the most effective microorganisms for PR solubilization ( Goenadi and Sugiarto , 2000; Abd‐Alla et al., 2001) ascribed, at least in part, to its high capability for the production of organic acids ( Grewal and Kalra , 1995; Schneider et al, 2010). Although it has been studied as a P‐mobilizing organism in organic substrates ( Vassilev et al, 2007) and different soils ( Li et al, 2015), little is known about its use as a P‐mobilizing microorganism or other potential benefits it may have in soil. Strain CBS513.88, in particular, has been widely used in industry for organic acid production ( Hertz‐Fowler and Pain , 2007).…”

Isolation and Characterization of a Phosphorus-Solubilizing Bacterium from Rhizosphere Soils and Its Colonization of Chinese Cabbage (Brassica campestris ssp. chinensis)

“…The bacterium was identified as B. cereus by 16S rRNA sequence analysis, which is a common method used to identify bacterial species (Clarridge, 2004; Coelho et al, 2011). Based on the analysis of the P-solubilization of YL6, the P-solubilization was the highest at 48 h. Recent studies also reported that the content of soluble P does not change over time (Zhao et al, 2014; Li et al, 2015; Osorio and Habte, 2015). This might be because PSB can secrete organic acids to degrade TCP to promote the content of soluble P in culture medium; thus, the content of soluble P does not decrease over time.…”

“…The use of PSB in sustainable agriculture has increasingly attracted the attention of scientists (Hameeda et al, 2008). At present, identified PSB primarily belong to the Pseudomonas, Bacillus, Mycobacterium , and Enterobacter genera, among others (Hanif et al, 2015; Li et al, 2015). Two types of P-solubilization mechanisms in PSB are generally believed to occur.…”