Reply to Singh: No archaea found but other rare phylotypes present

Abstract

The comments by B. Singh (1) on our recent article in PNAS (2) suggest that archaea may yet be detectable in the high inland Dry Valleys using alternative approaches, but we did employ those molecular approaches he suggests, and we did not find archaea. Our efforts in analyzing a large number of samples and using different archaeal-specific primers and PCR conditions, including nested PCR amplifications, were unsuccessful in detecting archaea. Our ongoing studies of other environments routinely yield archaeal signals with the same quantity of sample as used in this study and so we discount a laboratory-specific phenomenon. We add that our study successfully recovered relatively “rare” eukaryal phylotypes that comprised less than 1% of the total rRNA-defined community.