• A. W. Tani Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan
Keywords: Methanol, Methylobacterium sp. MALDI-TOF/MS


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.