FIG. 2.

Actinobacteria: diagrammatic tree showing the broad distribution of endolithic rRNA gene sequences. The open wedges represent the main recognized groups within the Actinobacteria (32). The solid wedges represent new actinobacterial groups formed by endolithic sequences (Endo-1 to Endo-6). Communities with sequences that belong to a group are indicated by four-letter codes that indicate the study site (FQ, Forest Quarry; EP, Exclamation Point; OC, Owl Canyon; SC, Sinks Canyon) and the rock type (SS, sandstone; LS, limestone; GR, granite). The general topology of the tree is supported by neighbor-joining bootstrap and Bayesian analysis (not shown) and is consistent with previous phylogenetic analyses (32).