Comparison of five bacterial strains producing siderophores with ability to chelate iron under alkaline conditions

Abstract

Iron deficiency is one of the main causes of chlorosis in plants, which leads to losses in field crops quality and yield. The use of synthetic chelates to prevent or correct iron-deficiency is not satisfactory mainly due to their poor biodegradability. The present work aimed to search suitable microorganisms to produce alternative, environment-friendly iron-chelating agents (siderophores). For this purpose, the performance of five bacteria ( Azotobacter vinelandii , Bacillus megaterium , Bacillus subtilis , Pantoea allii and Rhizobium radiobacter ) was evaluated, regarding siderophore production kinetics, level of siderophore production (determined by chrome azurol S, CAS method), type of siderophore produced (using Arnow and Csaky’s tests) and iron-chelating capacity at pH 9.0. All bacteria were in stationary phase at 24 h, except A. vinelandii (at 72 h) and produced the maximum siderophore amount (80–140 µmol L −1 ) between 24 and 48 h, with the exception of A. vinelandii (at 72 h). The analysis of culture filtrates revealed the presence of catechol-type siderophores for B. subtilis and R. radiobacter and hydroxamate-type siderophores for B. megaterium and P. allii . In the case of A. vinelandii , both siderophore-types (catechol and hydroxamates) were detected. The highest iron-chelating capacity, at pH 9.0, was obtained by B. megaterium followed by B. subtilis and A. vinelandii. Therefore, these three bacteria strains are the most promising bacteria for siderophore production and chlorosis correction under alkaline conditions. Electronic supplementary material The online version of this article (10.1186/s13568-019-0796-3) contains supplementary material, which is available to authorized users.

Phosphate-Solubilizing Microorganisms: Mechanism and Their Role in Phosphate Solubilization and Uptake

“…PSMs also release siderophores as a strategy to chelate iron from Fe-P complexes in the soil (Collavino et al 2010), although its role in phosphate dissolution needs to be further investigated. It was reported that under alkaline conditions, several phosphate solubilizers like Bacillus megaterium, Bacillus subtilis, Rhizobium radiobacter, and Pantoea allii produced siderophores in the range of 80 to 140 μmol L − 1 , which encouraged the survival of organisms under stress environment and also improved phosphorus solubilization (Ferreira et al 2019). Toscano-Verduzco et al (2020) found that novel fungi Beauveria brongniartii secreted siderophores, i.e., 59.8% of Fe 3+ -Chrome azurol-S degradation, and solubilized 158.95 mg L − 1 phosphorus in vitro.…”

Role of Dominant Phyllosphere Bacteria with Plant Growth–Promoting Characteristics on Growth and Nutrition of Maize (Zea mays L.)

“…The ability of siderophore production is an important strategy employed by some PGPB to influence the plant growth by binding to the available form of Fe under Fe-limiting conditions (Ferreira et al 2019) which significantly reduces the quality and quantity of crop production. Among the evaluated isolates, KUU32 (B. subtilis), KHU53 (B. paralicheniformis), ALB32 (P. putida), and QAZ26 (S. maltophilia) presented the ability of siderophore production.…”

Evaluation of the Efficacy of Two New Biotechnological-Based Freeze-Dried Fertilizers for Sustainable Fe Deficiency Correction of Soybean Plants Grown in Calcareous Soils

“…Bacterial filtrates were produced as described elsewhere (Ferreira et al, 2019b). Shortly, bacteria were grown in Fe-depleted media until siderophore concentration was stable (72 and 48 h for A. vinelandii and B subtilis , respectively).…”

“…To study the suitability of each bacterial media for Fe chlorosis remediation in soil applications, an Fe-siderophore solution (ISS) was prepared by rehydrating to the same volume the previously obtained powders; this procedure allowed to achieve the same initial concentration of siderophores. Then, a soluble salt of Fe(III), FeCl 3 .6H 2 O (Sigma), was added to the maximum complexation capacity at pH 9.0 ( A. vinelandii ≈ 188 µmol L −1 and B. subtilis ≈ 225 µmol L −1 ) of each solution, which was previously determined (Ferreira et al, 2019b). During the process, the pH of the solution was kept between 7.0 and 9.0, and the final pH was set at 9.0.…”