FIG. 1.

Evolutionary distance dendrogram showing the positions of environmental SSU rDNA sequences recovered from rice roots (ARR sequences) and anoxic bulk soil (ABS sequences) from flooded rice microcosms. The positions of sequences are shown in relation to the positions of known members of the Euryarchaeota and environmental sequences retrieved from peat bogs (R17 [16]) and from coastal marine environments (WHAR N and SBAR 16 [9]). The numbers at the nodes indicate the percentages of recovery in 1,000 bootstrap resamplings. The numbers in parentheses indicate whether the environmental sequences were recovered from 84-day-old flooded rice microcosms or 90-day-old flooded rice microcosms. SSU rDNA sequences of Aquifex pyrophilus and of members of the Crenarchaeota were used as outgroup reference sequences. The tree topology was determined by using distance matrix methods (calculation of the distance matrix with the Jukes-Cantor equation [20], construction of the distance tree by the neighbor-joining method [31]). Scale bar = 10% difference in nucleotide sequence positions.