Isolation Of Halophilous Methanogen From The Yahu Lake, Its Biological Characteristic, Phylogenetic Analysis And Carbon Monoxide Conversion By Anaerobic Bioreactor Sludges

A strain of methanogenic bacterium MQ-4 was isolated form the sediments of the west of yahu lake by Hungate roll-tube techhique.Cells of MQ-4 are Gram negative,nonmotile and coccoids (average diameter, 1 μm).Colony was transparence or yellow,roughly round.MQ-4 uses H₂/CO₂ or formate as substrates for CH4 formation .The strain grew best at pH values near 7.0, and Na⁺ concentration of 670mM,the optimal growth temperature was 35℃.The 16S rDNA gene of MQ-4 strain was amplified, cloned and sequenced. BLAST of the sequence in NCBI indicated that the species with close similarity to MQ-4 were from genus methanoculleus. The similarity values of 16S rDNA sequence between strain MQ-4and Methanoculleus marisnigri, Methanoculleus submarinus, Methanoculleus chikugoensis were 98%. The phylogenetic tree was producted from 16S rDNA of MQ-4 and other 8 species with the high similarity. MQ-4 was clustered with Methanoculleus marisnigri, Methanoculleus submarinus, Methanoculleus chikugoensis. Further experiments of DNA hybridize and "G+C" mensuration should be taken to determine the species of the MQ-4.