Evaluation of pink-pigmented facultative methylotrophic bacteria for phosphate solubilization

Abstract

Thirteen pink-pigmented facultative methylotrophic (PPFM) strains isolated from Adyar and Cooum rivers in Chennai and forest soil samples in Tamil Nadu, India, along with Methylobacterium extorquens, M. organophilum, M. gregans, and M. komagatae were screened for phosphate solubilization in plates. P-solubilization index of the PPFMs grown on NBRIP-BPB plates for 7 days ranged from 1.1 to 2.7. The growth of PPFMs in tricalcium phosphate amended media was found directly proportional to the glucose concentration. Higher phosphate solubilization was observed in four strains MSF 32 (415 mg l(-l)), MDW 80 (301 mg l(-l)), M. komagatae (279 mg l(-l)), and MSF 34 (202 mg l(-l)), after 7 days of incubation. A drop in the media pH from 6.6 to 3.4 was associated with an increase in titratable acidity. Acid phosphatase activity was more pronounced in the culture filtrate than alkaline phosphatase activity. Adherence of phosphate to densely grown bacterial surface was observed under scanning electron microscope after 7-day-old cultures. Biochemical characterization and screening for methanol dehydrogenase gene (mxaF) confirmed the strains as methylotrophs. The mxaF gene sequence from MSF 32 clustered towards M. lusitanum sp. with 99% similarity. This study forms the first detailed report on phosphate solubilization by the PPFMs.

Mechanisms for Solubilization of Various Insoluble Phosphates and Activation of Immobilized Phosphates in Different Soils by an Efficient and Salinity-Tolerant Aspergillus niger Strain An2

“…Previously, the highest level of soluble P production reported was 1164 mg L −1 from Ca-P by the strain Pantoea agglomerans R-42 [7] and 106, 92, and 130 mg L −1 from Al-P, Fe-P, and RP, respectively, by the strain Aspergillus fumigatus O4 [23]. The capacities for solubilization of Ca-P, Al-P, Fe-P, and RP of other strains were all below these values [4,5,24,[30][31][32], and the incubation time in these studies lasted 12 to 14 days in some cases [33]. Although few reports of microbial solubilization of Mg-P are available, An2 in this study solubilized Mg-P with a high capacity and efficiency.…”

“…Therefore, a large quantity of chemical phosphate fertilizers (P fertilizers) is applied to farmland to increase crop yields [3,4]. However, it is estimated that up to 75 % of the applied phosphate is immobilized rapidly to insoluble calcium/magnesium phosphate (Ca-P and Mg-P) in calcareous soils and to aluminum/iron phosphate (Al-P and Fe-P) in acidic soils, all unavailable for plants [5]. Severe P deficiency is also observed in large areas of saline-alkali soils worldwide [6].…”

Plant Growth Promoting Activity of Pink Pigmented Facultative Methylotroph - Methylobacterium extorquens MM2 on Lycopersicon esculentum L.

“…PPFMs are classified as α-proteobacteria, capable of growing even on single carbon compounds such as methanol and methylamine [3]. Methylobacterium are able to oxidize methanol in presence of methanol dehydrogenase (MDH) encoded by mxaF gene [4]. The presence of highly conserved mxaF gene in Methylobacterium is a molecular marker for identification, characterization and to study extent of diversity [5].…”

Cellulase Production by Pink Pigmented Facultative Methylotrophic Strains (PPFMs)

“…grown in the presence of tricalcium phosphate-containing medium was observed earlier (Jayashree et al [60] communicated to Archives of Microbiology). MNW 60 cells grown in methanol mineral salts medium were seen as long rods with smooth surfaces, and the cells grown in the medium containing CMC showed extensive morphological changes with adherence of cellulose-like particles and presence of some ultrastructural protuberances on the surface of the cells (Fig.…”