Archaeal community structures in rice soils from different geographical regions before and after initiation of methane production

The methane production potential of rice soils, which are situated in diffe rent geographical regions, shows inherent variations and is catalyzed by ar chaeal methanogens. We therefore investigated the archaeal community struct ure in 11 rice field soils which represent a range of climatic conditions ( temperate to subtropical zones) and soil properties. Retrieval of environme ntal partial SSU rDNA sequences from the rice soils of Shenyang (China) and Gapan (The Philippines) showed that the communities were different from ea ch other. However, despite the differences in soil properties and geographi cal region the sequences clustered in similar phylogenetic groups to those obtained earlier from rice fields of Vercelli (Italy). The archaeal communi ty structure in the other rice field soils was compared using terminal rest riction fragment length polymorphism (T-RFLP) analysis targeting the SSU rR NA gene and the methyl-coenzyme M reductase alpha -subunit gene (mer A). Th e relative abundance of each terminal restriction fragment (T-RF) was deter mined by fluorescence peak area integration. The 182-bp SSU rDNA T-RF (repr esenting members of Methanosarcinaceae and rice cluster (RC) VI) was domina nt (40-80% contribution) in Chinese soils (Zhenjiang, Changchun, Jurong, Be iyuan, Shenyang) and the Philippine soil of Gapan. The other Philippine soi ls (Luisiana, Guangzhou, Pila) and the Italian soils (Vercelli, Pavia) show ed a dominant 389-bp T-RF (35-40% contribution), representing mainly the no vel methanogenic RC-I. All the other T-RF (80, 88, 280, 375 and > 800 bp) c ontributed < 20%. Prolonged anoxic incubation (30-200 days) of the air-drie d soils resulted in the production of CH4, which was in some soils preceded by a characteristic halt phase, T-RFLP analysis revealed that the soils wi th a methanogenic halt phase also showed dramatic archaeal population dynam ics which were related to the length of the halt phase. Our results show th at the archaeal communities in rice field soils of different geographical o rigin are highly related, but nevertheless exhibit individual patterns and dynamics, thus providing evidence for the active participation of the commu nity members in energy and carbon flow. (C) 2001 Federation of European Mic robiological Societies. Published by Elsevier Science B.V. All rights reser ved.