Are rare earth elements essential for growth of microorganisms?

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The rare earth elements have been used for various high technology products. We have been screening microorganisms which show a peculiar growth in the presence of rare earth elements. We had isolated successfully some rare-earth responsive microorganisras(sliains EU-1, EU-2 and EU-3). In thisresearch, we investigated on three strains (EU-1, EU-2 and EU-3) which formed the bigger colony size in the presence of europium (Eu). Strain EU-1 was identified as Methylobactetizun sp. The growthof this strain was stimulated by Sm on 1/100 nutrient agar plate with methanol. The growth of this bacterium increased about 10-times when Sm was added to the liquid medium, suggesting that Sm was involved in the methanol metabolism of this bacterium. Strain EU-2 was identified as Nevskia ramosea. The growth of strain EU-2 was found to be increased by Eu on a soft agar: This indicated that the mobility of this bacterium was controlled by Eu. Although the viable cells were increased 20 times by adding Eu t … More o the medium, some dispersion of the colony munber appeared on the plate was found. This was due to the aggregation of the cells especially in the absence of Eu Strain EU-3, identified as Sphingomonas sp. EU-3, when the cell growth was reached to stationary phase, immediately the cells went into the death phase. La addition to the medium, however, the stationary phase in was continued. La have uhvsiolotlically important role in survival of strain EU-3.Methylobactelium sp.EU-1 was cultivated in the medium containing methanol and light rare earth elements, activity of methanol dehydrogenase in crude extracts of Afethylkobacterium sp. EU-1 was markedly increased. Especially La or Ce caused the increment of methanol dehydrogenase activity about 150 times. The dehydrogenase was purified.The purified enzyme migrated as a single band on SDS-PAGE. The N-terminal amino acid sequence of the dehydrogen-ase showed the high similarity with methanol dehydrogenase or PQQ-dependent dehydrogenase of Methylobacteiitun spp. Furthermore, the absorption spectra of the dehydrogenase revealed that this dehydrogenase was a member of PQQ-dependent dehydrogenase family.These results indicated a biological importance both in viva and in vitro of rare earth elements and will give a great impact to the fields of bioinorganic chemistry. Less