Insights Into Manganese Solubilizing Bacillus spp. for Improving Plant Growth and Manganese Uptake in Maize

Abstract

Manganese (Mn) is an essential micronutrient for plant growth that is involved in the structure of photosynthetic proteins and enzymes. Mn deficiency is widespread mainly in dry, calcareous, and sandy soil, which leads to a significant decrease in crop yield. Mn-reducing bacteria promote the solubilization of Mn minerals, thus increasing Mn availability in soil. The present study aimed to assess the Mn solubilizing ability and plant growth-promoting potential of Bacillus spp. strains for maize plants with insoluble Mn compounds. Several Mn-solubilizing bacterial (MSB) strains were isolated from the maize rhizosphere using nutrient agar media amended with 50 mM MnO2. These strains were screened based on qualitative and quantitative solubilization of Mn, phosphorus, potassium, and zinc and production of ammonia. The majority of MSB strains were positive for catalase, protease, amylase, and oxidase activity, while more than 60% of tested strains were positive for lipase activity, and the production of indole-3-acetic acid and siderophores. Forty-five percent of the tested strains also showed solubilization of potassium. All the MSB strains were evaluated for their ability to promote plant growth and Mn uptake in the presence of MnO2 under axenic sand culture conditions. The results revealed that inoculation with MSB strains under sand culture significantly improved the growth of maize seedlings except for strains ASH7, ASH10, and ASH12. Comparatively, strains ASH6, ASH11, ASH19, ASH20, and ASH22 demonstrated a better increase in plant growth, fresh and dry biomass, and Mn uptake in roots and shoots than the other strains tested. All of these strains were identified as Bacillus spp. through 16S rRNA partial gene sequencing. Maize inoculation with these selected identified MSB strains also resulted in an increase in maize growth and nutrient uptake in maize roots and shoots under soil culture conditions in the presence of native soil Mn. The current study highlights the importance of MSB strain inoculation which could be a potential bioinoculants to promote plant growth under Mn deficiency.

Potential of mineral-solubilizing bacteria for physiology and growth promotion of Chenopodium quinoa Willd

“…These strains were also screened for Mn solubilization by growing bacterial strains on nutrient agar amended with MnO 2 (50 mM) at 30 ± 1°C for 72 h ( Sanket et al., 2017 ). After incubation, Mn amended nutrient agar plates were flooded with iodine solution as an indicator to observe a clear halo zone ( Ijaz et al., 2021 ). The clear halo zone and bacterial growth zone diameters were recorded through meter rod, and Mn solubilization index (MSI) and Mn solubilization efficiency (MSE) were calculated by following formulas reported by Ijaz et al.…”

“…After incubation, Mn amended nutrient agar plates were flooded with iodine solution as an indicator to observe a clear halo zone ( Ijaz et al., 2021 ). The clear halo zone and bacterial growth zone diameters were recorded through meter rod, and Mn solubilization index (MSI) and Mn solubilization efficiency (MSE) were calculated by following formulas reported by Ijaz et al. (2021) .…”

The “Infernaccio” Gorges: Microbial Diversity of Black Deposits and Isolation of Manganese-Solubilizing Bacteria

“…Among the Mn-oxide-solubilizing bacteria, most of the isolates belonged to Bacillus spp. Several species of this genus have been described for their Mn solubilization abilities under aerobic and anaerobic conditions [ 35 ]. Sanket et al described Mn solubilization by the strains B. cereus AMSB3 and B. nealsonii AMSB4 isolated from mine water samples [ 36 ].…”

“…Sujith et al described Mn-reducing abilities for Brevibacterium epidermidis NA5 [ 38 ]. P. aryabhattai is a novel Bacillaceae genus [ 39 ], previously known as Bacillus aryabhattai , which has also been described for Mn-oxide-solubilizing abilities [ 35 ]. Brevibacterium spp.…”

Combined Use of Novel Endophytic and Rhizobacterial Strains Upregulates Antioxidant Enzyme Systems and Mineral Accumulation in Wheat

“…As these constituents are also acquired by the native microbes and their application, the microbial population results in heterogeneity. These colonies make essential nutrients available by solubilization and mineralization, causing a higher concentration of these elements in plants [54]. The inoculation of Rhizobium and rhizospheric bacteria separately raised nitrogen supply to plants due to gain in nodule formation, and they supported the activity in the rhizosphere [13,42].…”