title: Thermophilic methanogens in rice field soil.
abstract: The soil temperature in flooded Italian rice fields is generally lower than 30 degrees C. However, two temperature optima at approximately 41 degrees C and 50 degrees C were found when soil slurries were anoxically incubated at a temperature range of 10-80 degrees C. The second temperature optimum indicates the presence of thermophilic methanogens in the rice field soil. Experiments with 14C-labelled bicarbonate showed that the thermophilic CH4 was exclusively produced from H2/CO2. Terminal restriction fragment length polymorphism (T-RFLP) of archaeal SSU rRNA gene fragments revealed a dramatic change in the archaeal community structure at temperatures > 37 degrees C, with the euryarchaeotal rice cluster I becoming the dominant group (about 80%). A clone library of archaeal SSU rRNA gene fragments generated at 49 degrees C was also dominated (10 out of 11 clones) by rice cluster I. Our results demonstrate that Italian rice field soil contains thermophilic methanogenic activity that was most probably a result of members of the as yet uncultivated euryarchaeotal rice cluster I.
authors: Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Str., 35043 Marburg, Germany.
authors: A
authors: A
authors: Fey
authors: K J
authors: KJ
authors: Chin
authors: R
authors: R
authors: Conrad
mesh_terms: D000693:Anaerobiosis; D002248:Carbon Monoxide / Q000378:metabolism; D019641:DNA, Archaeal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D017753:Ecosystem; D019605:Euryarchaeota / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D008697:Methane / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000502:physiology*; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology; D013696:Temperature; D013816:Thermodynamics
chemical_list: D019641:DNA, Archaeal; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D002248:Carbon Monoxide; D006859:Hydrogen; D008697:Methane