%0 Journal Article %A Mori, K %A Yamamoto, H %A Kamagata, Y %A Hatsu, M %A Takamizawa, K %T Methanocalculus pumilus sp. nov., a heavy-metal-tolerant methanogen isolated from a waste-disposal site. %D 2000 %J International Journal of Systematic and Evolutionary Microbiology, %V 50 %N 5 %P 1723-1729 %@ 1466-5034 %R https://doi.org/10.1099/00207713-50-5-1723 %I Microbiology Society, %X A mesophilic hydrogenotrophic methanogen, strain MHT-1T, was isolated from the leachate of a sea-based site for solid waste disposal (the port of Osaka, Japan). Strain MHT-1T was found to be an irregular coccus and was able to use H2/CO2 and formate as energy sources. Acetate was required for growth. The optimum temperature and pH for growth were 35 degrees C and 6.5-7.5, respectively. Strain MHT-1T was resistant to high concentrations of several heavy metals such as CdCl2 and CuSO4. The G+C content of the DNA was 51.9 mol%. Analysis of the 16S rRNA gene revealed that the isolate was a member of the genus Methanocalculus but distinct from its nearest neighbour, Methanocalculus halotolerans, there being a sequence similarity of 98.9%. DNA-DNA hybridization analysis revealed 51% relatedness with the DNA of M. halotolerans strain SEBR 4845T. The optimum NaCl concentration was 1.0%, whereas the optimum in M. halotolerans was 5.0%. A new species, Methanocalculus pumilus, is proposed for strain MHT-1T. The type strain is MHT-1T (= DSM 12632T = JCM 10627T). %U https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/00207713-50-5-1723