Ethyl Methanesulfonate Mutagenesis–Enhanced Mineral Phosphate Solubilization by Groundnut-Associated Serratia marcescens GPS-5

Abstract

Twenty-three bacterial isolates were screened for their mineral phosphate-solubilizing (MPS) ability on Pikovskaya and National Botanical Research Institute's phosphate (NBRIP) agar. The majority of the isolates exhibited a strong ability to solubilize hydroxyapatite in both solid and liquid media. The solubilization in liquid medium corresponded with a decrease in the pH of the medium. Serratia marcescens GPS-5, known for its biocontrol of late leaf spot in groundnut, emerged as the best solubilizer. S. marcescens GPS-5 was subjected to ethyl methanesulfonate (EMS) mutagenesis, and a total of 1700 mutants, resulting after 45 minutes of exposure, were screened on buffered NBRIP medium for alterations in MPS ability compared with that of the wild type. Seven mutants with increased (increased-MPS mutants) and 6 mutants with decreased (decreased-MPS mutants) MPS ability were isolated. All seven increased-MPS mutants were efficient at solubilizing phosphate in both solid and liquid NBRIP medium. Among the increased-MPS mutants, EMS XVIII Sm-35 showed the maximum (40%) increase in the amount of phosphate released in liquid medium compared with wild-type S. marcescens GPS-5, therefore, it would be a useful microbial inoculant in groundnut cultivation. EMS III Sm W, a nonpigmented mutant, showed the lowest solubilization of phosphate among the 6 decreased-MPS mutants.

Phosphate solubilization and multiple plant growth promoting properties of rhizobacteria isolated from chickpea (Cicer aeritinum L.) producing areas of Ethiopia

“…It has been well documented that mineral phosphate solubilization by phosphate solubilizing bacteria strains results from the release of low molecular weight organic acids (Illmer and Schinner, 1995;Kim et al, 1997;Vyas and Gulati, 2009), probably as an interacting effect of their hydroxyl or carboxyl groups that may chelate the cations bound to the phosphate, thereby converting it into soluble forms (Kpomblekou and Tabatabi, 1994;Kim et al, 1997). Gram negative isolates displayed better performance in solubilization of different insoluble inorganic P sources compared to Gram positive phosphate solubilizing bacterial isolates in the study which is in line with the results of previous studies (Muleta et al, 2013;Tripura et al, 2007). The fluctuations and differences in insoluble P sources solubilization efficiency observed among the isolates could be attributed to differences in the types and the amount of organic acids produced (Vyas and Gulati, 2009).…”

“…From our the observation in this study, a decrease in soluble P and concomitant increase in the pH values of the growth medium indicates re-utilization of available P (Rashid et al, 2004;Tripura et al, 2007). In addition, the excreted organic acids could be reused by the isolates for their own metabolism (Tripura et al, 2007) which is highly associated with an exhaustion of the original carbon source (Rashid et al, 2004) since phosphate solubilization is a complex process depending on many factors such as nutritional, physiological and growth conditions of the culture (Reyes et al, 1999).…”

“…Alternatively, it could also be explained by the differences of in rate of P release and immobilization (Muleta et al, 2013;Prasanna et al, 2011), when cells in the culture immobilize more phosphate for microbial biomass production, the corresponding values decrease, creating such fluctuations (Muleta et al, 2013). From our the observation in this study, a decrease in soluble P and concomitant increase in the pH values of the growth medium indicates re-utilization of available P (Rashid et al, 2004;Tripura et al, 2007). In addition, the excreted organic acids could be reused by the isolates for their own metabolism (Tripura et al, 2007) which is highly associated with an exhaustion of the original carbon source (Rashid et al, 2004) since phosphate solubilization is a complex process depending on many factors such as nutritional, physiological and growth conditions of the culture (Reyes et al, 1999).…”

Characterisation of Phosphate Solubilising Bacteria in Sandy Loam Soil Under Chickpea Cropping System

“…Similarly, TCP solubilization ranged from 96 to 139 lg/mL by the 13 best isolates clustered under the genera Enterobacter, Pantoea, and Klebsiella from Korean soils [24]. A significant decline in the pH of medium was recorded during the solubilization of TCP, which suggested secretion of organic acids by the bacterial isolates [25,26]. The release of soluble phosphates is not necessarily correlated with soil pH [27].…”

Endophytic bacteria from Piper tuberculatum Jacq.: isolation, molecular characterization, and in vitro screening for the control of Fusarium solani f. sp piperis, the causal agent of root rot disease in black pepper (Piper nigrum L.)

“…Additionally, Pseudomonas bacteria are considered plant growth-promoting bacteria (PGPB) due to many traits, which contribute to the growth and development of plants, such as the production of phytohormones and siderophores (Glick, 2012). Serratia marcescens and Pantoea agglomerans are also PGPB, since they can control plant disease (Hsieh et al, 2005) and promote plant growth (Selvakumar et al, 2007), cause solubilization of phosphates (Tripura et al, 2007), and cold tolerance (Selvakumar et al, 2007). We also identified four potential PGPB (Pt17,18,19,and 20) that are associated with the α-Proteobacteria class.…”