Maize endophytic bacteria as mineral phosphate solubilizers

Abstract

ABSTRACT. In the present study, we demonstrated the in vitro activity of endophytic phosphate-solubilizing bacteria (PSB). Fifty-five endophytic PSB that were isolated from sap, leaves, and roots of maize were tested for their ability to solubilize tricalcium phosphate and produce organic acid. Partial sequencing of the 16S rRNA-encoding gene showed that the isolates were from the genus Bacillus and different species of Enterobacteriaceae. The phosphate solubilization index on solid medium and phosphate solubilization in liquid medium varied significantly among the isolates. There was a statistically significant difference (P ≤ 0.05) for both, the values of phosphatesolubilizing activity and pH of the growth medium, among the isolates. Pearson correlation was statistically significant (P ≤ 0.05) between P-solubilization and pH (R = -0.38), and between the gluconic acid production and the lowering of the pH of the liquid medium at 6 (R = 0.28) and 9 days (R = 0.39). Gluconic acid production was prevalent in all the PSB studied, and Bacillus species were most efficient in solubilizing phosphate. This is the first report on the characterization of bacterial endophytes from maize and their use as potential biofertilizers. In addition, this may provide an alternative strategy for improving the phosphorus acquisition efficiency of crop plants in tropical soils.

Endophytic Bacillus strains enhance pearl millet growth and nutrient uptake under low-P

“…The efficiency of phosphate solubilization by microorganisms depends on the nature of the P source and the organisms involved in the process. We selected from a previous screening in vitro , four Bacillus isolates that contrasted for Ca-P solubilization 21 to be characterized for their capacity to solubilize Fe-P, that is the most abundant and least soluble P fraction in Brazilian Oxisols. 3 , 4 In addition, we assessed siderophore and IAA production, followed by a greenhouse test to assess their effect on plant growth promotion.…”

“…Our results of soluble P released by Bacillus grown on a medium containing FePO 4 varied from 34.25 to 52.22 mg L −1 and were lower than the previously reported values for Ca-P solubilization by the same isolates, which ranged from 112 to 179 mg L −1 . 21 Similar results, reported previously with different bacterial species, have shown that Fe-P and Al-P are less soluble than Ca-P. 31 , 32 The highest Fe-P solubilization has been documented in rhizobacteria and fungi 4 , 32 , 33 ; however, our isolates showed higher solubilization than reported for endophytic bacteria isolated from peanuts, that ranged from 13.9 ± 0.3 to 37.4 ± 2.0 mg L −1 . 12 In our study, the inoculated strains decreased the growth medium pH and simultaneously increased the concentration of soluble phosphate obtained from FePO 4 .…”

“…Four endophytic Bacillus strains, B1920, B1923, B2084, and B2088, previously isolated from maize sap, roots, and leaves, 21 were analyzed for Fe-P solubilization in liquid culture. The strains were reactivated on PDA plates (200 g L −1 of potato, 20 g L −1 of dextrose and 15 g L −1 of agar), using the method of streaking for obtaining pure colonies.…”

“…Previously, in our laboratory, endophytic Bacillus strains isolated from the roots, leaves, and sap of maize showed Ca-P-solubilizing and organic acid-producing ability in vitro . 21 Bacterial strains that solubilize P-Ca showed potential as PGPs in soils fertilized with hydroxyapatite rock phosphate (RP) rich in Ca. 22 In the present study, four of these Bacillus isolates were selected, representing high (B1920 and B2088) and low (B2084 and B1923) Ca-P-solubilizing ability, to characterize their capacity to produce siderophores and IAA and solubilize Fe-P.…”

Bactérias Solubilizadoras De Fosfato inorgânico em solo Preservado E Antropizado Da Reserva Biológica de Pedra Talhada – Al

“…Microrganismos solubilizadores de fosfatos e o manejo de suas populações tem sido sugerido como forma de substituir ou diminuir o uso de fertilizantes fosfatados solúveis, melhorando o aproveitamento dos fosfatos naturais existentes ou adicionados ao solo e aplicação de fontes solúveis, dessa forma, contribuindo para reduzir a dependência de fertilizantes importados, os custos da produção agrícola e também os impactos ambientais (GOLDSTEIN, 1986;KIM et al, 1998;GOMES et al, 2014). Os microrganismos utilizam diferentes mecanismos para transformar formas pouco solúveis de fosfato em solúveis, como processos de acidificação, quelação e reações de troca, mas o principal mecanismo de solubilização é a liberação de metabólitos como ácidos orgânicos e enzimas extracelulares (HAMEEDA et al, 2008;YOUNG et al, 2013BALIAH et al, 2016ABREU et al, 2017;). Outro mecanismo provável de solubilização de fosfatos, principalmente o fosfato de ferro (estrengita), é a produção de sideróforos, que são moléculas orgânicas de baixo peso molecular produzidas por algumas espécies de microrganismos, cuja função principal é complexar metais, em especial ferro em estado insolúvel (BATISTA et al, 2018).…”