Characterization of Ni-tolerant methylobacteria associated with the hyperaccumulating plant Thlaspi goesingense and description of Methylobacterium goesingense sp. nov.

Various pink-pigmented facultative methylotrophic (PPFM) bacteria (strains iEII3, iEIV1, iEI6, iEII1, iEIII3 iEIII4, iEIII5, iRII1, iRII2, iRIII1, iRIV1 and iRIV2) were obtained from the rhizosphere and endosphere of hyperaccumulating plant Thlaspi goesingense grown in Redschlag, Austria [R. Idris, R. Trifonova, M. Puschenreiter, W.W. Wenzel, A. Sessitsch, Bacterial communities associated with flowering plants of the Ni hyperaccumulator Thlaspi goesingense, Appl. Environ. Microbiol. 70 (2004) 2667-2677]. Due to their unexpected diversity, abundance and nickel tolerance they were further characterized by detailed 16S rRNA gene analysis, DNA-DNA hybridization, fatty acid analysis, heavy metal tolerance, screening for known Ni resistance genes and phenotypic analysis. These strains were found to exhibit different multiple heavy metal resistance characteristics to Ni, Cd, Co, Zn and Cr. On the basis of their physiological and genotypic properties, strains could be grouped with Methylobacterium extorquens and M. mesophilicum. One endophyte, strain iEII3, was found to belong to a novel species for which the name M. goesingense is proposed.