Investigation of Newly Isolated Methylobacterium sp. as Potential Biofertilizer

Abstract

Methylobacterium sp. are pink-pigmented facultative methylotrophs (PPFMs) that can promote plant’s growth due to several physiological characteristics such as the ability to produce phytohormone namely indole acetic acid (IAA) and effective roles in phosphate solubilization and nitrogen fixation process. Members of this genus are ubiquitous in the environment and characterized by its ability to utilize single C compound such as methanol as its energy source. These characteristics made Methylobacterium sp. as potential candidates for biofertilizer. In this study, Methylobacterium sp. were isolated from the leaves of paddy and palm oil tree using Ammonia Mineral Salt (AMS) agar supplemented with methanol. Nine isolates were selected based on the appearance of pink colonies on AMS agar. Several analyses were conducted to evaluate plant growth-promoting activities of the selected isolates. The production of IAA was quantified spectrophotometrically using Salkowski’s reagent, and solubilization of inorganic phosphate was determined using vanadate molybdate assay. The results showed that, all the isolates are capable to produce IAA and solubilize inorganic phosphate. As for nitrogen fixation, the lack/poor growth of the isolates on two nitrogen-free media, namely Burks’s and Jensen media manifested the absence or weak nitrogen fixing activity. Findings from these qualitative and quantitative analyses are vital and it will serve as preliminary data for the future exploration of Methylobacterium sp. as biofertilizer.