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Characterization of Phosphate Solubilising Methylorubrum sp. Isolated from Paddy (Oryza sativa) Leaves
Faculty of Bioengineering and Technology, Universiti Malaysia Kelantan, 17600 Jeli, Kelantan, Malaysia
*Email Address : ainihayati@umk.edu.my
Abstract : Methylorubrum sp., formerly categorized as Methylobacterium sp., exhibit a pink pigment and are facultative methylotrophs known as PPFMs. They possess the unique capability to thrive exclusively on organic one-carbon (C1) compounds, including formate, formaldehyde, methanol, and methylamine. Previous research has identified Methylorubrum members as contributors to seed germination and plant growth enhancement. This beneficial effect is attributed to their synthesis of plant hormones like auxins or cytokinins suggesting their potential as a candidate for biofertilizer. Three endophytic PPFM strains namely ENPD1, ENPD2, and ENPD3 were successfully isolated from the internal tissue of the paddy leaves and identified as having the highest similarity to Methylorubrum salsuginis, Methylorubrum zatmanii, and Methylorubrum sp. respectively. Besides, two epiphytic PPFM strains namely EPPD1 and EPPD4 were isolated from paddy leaves surfaces and identified as having the highest similarity to Methylorubrum rhodinum and Methylorubrum thiocyanatum respectively. Phosphate solubilisation activity of the total five isolates was evaluated by phosphate solubilisation index (PSI) test, vanadate molybdate assay and phytase assay. All PPFMs isolates are able to solubilize phosphate with solubilisation index (SI), phosphate solubilisation activity, and phytase activity varies from 0.000 ± 0.000 to 1.222 ± 0.082, 172.802 ± 17.184 to 182.484 ± 27.149 µg/L, and 28.219 ± 4.360 U/mL to 46.901 ± 5.275 U/mL respectively. M. rhodinum EPPD1 demonstrated the most substantial SI, whereas M. zatmanii ENPD3 exhibited the greatest levels of phosphate solubilization and phytase activity. Alongside phytohormone synthesis, effective phosphate solubilization is a pivotal trait in biofertilizer advancement. Consequently, the capacity of these isolates of Methylorubrum sp. to enhance plant growth will undergo comprehensive evaluation through an in vivo pot study.
Keywords : Methylorubrum sp, phosphate solubilisation, phosphate solubilisation index, phytase, biofertilizer