Ecology of Methylobacterium on the Phylloplanes in Pinus densiflora Forest

Abstract

Pink-pigmented facultatively methylotrophic bacteria (PPFMs) were isolated from fourteen kinds of phylloplanes in Pinus densiflora forest. PPFMs were Gram-negative, lophotrichously flagellated rods and attacked glucose fermentatively. All pink isolates utilized methanol, methylamine and formic acid as the sole carbon source but did not utilize methane. The PPFMs belonged to the genus Methylobacterium. The methylobacteria were found on the every phylloplane of the plants in P. densiflora forest. The fluctuation pattern in population of Methylobacterium was summerized as follows : (1) On the living leaves of Pinus densiflora, Methylobacterium occurred abundantly during summer although the number decreased abruptly in winter. The airborne methylobacteria behaved in the similar way as on the pine phylloplane. (2) On the phylloplanes of Cryptomeria japonica, Juniperus rigida and Ilex pedunculosa, these bacteria occurred even in winter. (3) Methylobacterium disappeared during the period from November to January on the leaves of Chamaecyparis obtusa and Eurya japonica. (4) Through the year round, higher occurrence of Methylobacterium was observed on the each phylloplane of the deciduous trees (Rhododendron macrosepalum, R. reticulatum, Lyonia elliptica, Quercus serrata, Rhus sylvestris, Vaccinium hirtum and Evodiopanax innovans) . These results indicate that Methylobacterium may reside favorably on the leaves of such plants as if it was epiphytic.