MALDI-TOF/MS BASED SCREENING OF PLANT-GROWTH PROMOTING METHYLOBACTERIUM SPECIES COLLECTED FROM VARIOUS PLANTS

Abstract

Plants emit many kinds of volatile organic compounds, including methanol as a main compound. The global methanol emission from plants is estimated at 100 mega tones per year. Recent metagenomic analysis revealed the predominance of Methylobacterium species in phyllosphere (plant surface). These species are characterized by their ability to grow on methanol as a sole carbon and energy source. Thus it is considered that such ability is advantageous for these species to grow in relatively nutrient-poor environment as plant surfaces. Also these species are known to have an ability to promote plant growth. They are reported to produce phytohormones (auxin, cytokinin), siderophores, and vitamin B12, and to have ACC deaminase that can inhibit ethylene biosynthesis. Also they have abilities of calcium phosphate solubilization and nitrogen fixation. These abilities are believed to be involved in plant growth promotion. The genus Methylobacterium contains 35 known species, and there is an increasing number of new isolates. But the interaction specificities between them and plants, and specificity of plant-growth promotion ability is not clear yet 200 strains of Methylobacterium from various plants were collected and subjected to MALDI-TOF/MS analysis for protein profiling of the isolates. The technique allowed identification and clustering of the isolates in a day. The selected unique strains were further subjected to 16S rRNA gene analysis, and their phylogenetic position was revealed. Using the same unique strains, efforts are in placeto find the best combination of strains and plant species. In this presentation I would like to introduce the result of the screening and the effect of inoculation to barley are discussed. As a conclusion, MALDI-TOF/MS-based screening allows maximization of isolates library, fast identification, and selection of unique strains. The technique can be used to find the best strain for specific plants.