Fig. 2.

Collector's curves of observed and estimated SLOTU richness of pooled forearm skin samples from six healthy subjects. (A) Each curve reflects the series of observed (Sobs) or estimated (Chao1) richness values obtained as the 1,221 16S rDNA clones are added to the data set in an arbitrary order. As reported for the human colon (23), as an increasing proportion of SLOTUs have been encountered, the Chao1 curve rises less steeply; however, additional SLOTUs continue to be identified to the end of the sampling. Although 182 (95% C.I., range 169–195) SLOTUs were observed, the Chao1 score of total species richness, estimates that the skin bacterial biota in the six subjects contains ≈246 SLOTUs (95% C.I., range 217–301). Based on this prediction, the present study identified 74.0% (95% C.I., 64.8–77.9%) of the SLOTUs in this bacterial ecosystem. (B) When results from resampling of four of the subjects with 817 new clones were included, the number of SLOTUs was 247 (95% C.I., range 232–262), and the Chao1 was 328 (95% C.I., range 295–385), indicating coverage of 75.3% (95% C.I., range 68.1–78.6).