Phosphate Solubilization by <i>Bacillus subtilis</i> and <i>Serratia marcescens</i> Isolated from Tomato Plant Rhizosphere

Abstract

Plants need phosphorus for many physiological activities in a form of phosphate anions. Three different bacterial strains (Bacillus subtilis PH, Serratia marcescens PH1, and Serratia marcescens PH2), recently isolated from tomato plant rhizosphere, have high phosphate solubilization index (SI from 2.8 to 3.2) on Pikovskaya agar medium (which contains calcium phosphate). Moreover, phosphate release from calcium in Pikovskaya broth over 5 days is increasing with cell growth for the different isolates. The most efficient phosphate solubilization case is the mixed culture of the 3 strains (OD 475 is almost 1). On the other hand, pH values decreased dramatically with time due to organic acids secretion and the maximum acidification level is recoded for Serratia marcescens PH2 (pH = 1.94). Interestingly, the isolates are resistance to important pesticides (oxamyl, thiophanate methyl, and captan) that are commonly used in the sampling area. This resistance is very favorable and increases the persistence of the phosphate solubilizing bacteria in contaminated soils. The isolates are therefore plant symbionts and growth promoting agents.

The Composition and Phosphate-Solubilizing Capability of Phosphate-Solubilizing Bacteria in the Rhizosphere of Wild<i> Camellia oleifera</i> in Mountain Lushan

“…showed the highest phosphate-solubilizing capability with a PSI value of 3.05 ± 0.13 after 6 days incubation, higher than the report from Sengupta et al [24] and Yasmin and Bano [25] that tested on Picovskaya's agar media using tricalcium phosphate as the sole P source. Previous studies reported that the most significant solubilizers of phosphate are mainly belonging to Bacillus and Pseudomonas [12,[26][27][28]. However, in our study, Burkholderia species were easier to be isolated and showed a high phosphate-solubilizing potential (Figure 4).…”

Enhancing Application Efficiency of Pseudomonas SPP. and Serratia marcescens Isolates against Meloidogyne incognita in Tomato Plants.

“…As, PGPB enhance phytoremediation by the production of siderophores (Tahir et al, 2013), phytohormones, and chelators in addition to their ability to biodegrade contaminants and facilitate their removal (Chun et al, 2020) or S. marcescens ABHI001 in the bioremediation of organic pollutants, such as p-cresol (Singh et al, 2017). Also, PGPB used as a biofertilizer can dissolve phosphate highly and making available for plants (Akhtar et al, 2012;Mohamed et al, 2018). Besides, PGPB can be mixed with different agrochemicals e.g.…”

“…Besides, PGPB can be mixed with different agrochemicals e.g. mineral fertilizers and pesticides without reducing its efficiency (Esfahani et al, 2016;Mohamed et al, 2018;Saedi et al, 2017). PGPB showed potency against a wide range of pests e.g.…”

“…Perhaps this increase is due to several reasons, including the availability elements necessary for plant growth clutched on soil particles by siderophores and chelators secrete by PGPB in the rhizosphere (Chun et al, 2020;Khatamidoost et al, 2015). Besides the ability to dissolve phosphorous as well as the secretion of plant hormone (indole acetic acid ) that lead to the superiority of inoculated plants (Khan et al, 2016;Mohamed et al, 2018). Raising plant resistance after inoculation with PGPB causing root colonization.…”

Dual Activity of Serratia Marcescens Pt-3 in Phosphate-solubilizing and Production of Antifungal Volatiles

“…Bacterial clones with clear halo zone in phosphate media were considered as PSB and selected for further use. The phosphate solubilizing index (PSI) was calculated as the following equation [20,21]. PSI = (colony diameter + halozone diameter)/colony diameter ×100.…”