FIG. 1.

Phylogenetic tree for nearly complete SSU rRNA sequences of environmental clones from oxygen-depleted water in the Great Sippewisset salt marsh, Cape Cod, Mass., and the most closely related cultured organisms and environmental 18S rRNA signatures. Environmental clones are indicated by boldface type, and each clone is designated by the library designation (CCW) followed by a number. The tree topology was obtained by a heuristic search with stepwise addition of taxa (TBR branch swapping) under a Tamura Nei minimum evolutionary distance model, with gapped and ambiguously aligned positions excluded. Distance bootstrap values over 50% from an analysis of 1,000 bootstrap replicates are given at respective nodes. Sequences are followed by GenBank accession numbers.