Biogeography, genetic and functional diversity of plant growth promoting phyllosphere methylotrophs
Phyllosphere methylotrophic bacteria are a group of bacteria, which inhabit plant surfaces, mainly the leaves of plants. They use one-carbon compounds such as methane or methanol as their sole carbon and energy source and play an important role in the methanol cycle by utilizing the methanol emitted by plants. On the other hand, these bacteria could be able to produce plant growth promoting substances like auxins, cytokinins, and vitamin B12.
Little is known about the diversity and distribution of methylotrophs. The objective of this project is to analyse the genetic diversity, biogeography, and functional role of phyllosphere methylotrophs in dependence of inhabited plant species, land-use type and geographic location. Pink-pigmented facultative methylotrophs (PPFM) add up to 79% of the total number of the heterotrophs found in the phyllosphere. That is why this subgroup of the methylotrophs will be the main focus of our project.
1. The diversity of methylotrophic bacteria is dependent on the land use intensity, the host plant species and the spatial distribution.
2. The production of plant growth promoting substances by methylotrophic bacteria is dependent on the microbial species composition and the land use intensity.
3. The genetic variability within a species correlates with land use intensity and / or geographic distance.
Leaf samples of Trifolium repens (white clover), Cerastium holosteoides (common mouse-ear) und Plantago lanceolata (ribwort plantain) were collected from sampling sites with different land-use types. To investigate the concentration of the PPFM per g leaf weight, the bacteria isolated from the leaf samples were cultivated on selective medium supplemented with methanol. For representative isolates, the 16S rRNA genes were sequenced and the resulting sequence information was used for phylogenetic analyses. Intraspecies diversity was studied by sequencing the mxaF-gene of selected isolates. The mxaF-gene codes for the ?-subunit of the methanoldehydrogenase which is present in all methylotrophs. In the near future the composition of the phyllosphere methylotrophs inhabiting the different leaf samples will be studied by fingerprinting methods (DGGE).
Erste Ergebnisse sind:
- Landnutzungstypen und Pflanzenarten haben einen signifikanten Einfluss aufdie Konzentration von methylotrophen Bakterien auf Blattoberflächen.
- Fünf phylogenetisch verschiedene Methylobacterium Gruppen einschl. drei neuer Arten wurden gefunden.
- Die Artenzusammensetzung der methylotrophen Bakterien ist nicht durch die Landnutzung beeinflusst.