ANCIENT PRIMARY SALT CRYSTALS CONTINUE TO YIELD LIVE MICROBES: ISOLATION OF THE OLDEST KNOWN ARCHAEA FROM 121 MYA HALITE

Numerous recent reports have described the isolation and analysis of either living microbes or DNA fragments from sodium chloride crystals of significant geological age. The overall heterogeneous distribution of survivors and the small number of laboratories equipped or funded to perform this type of research still hampers efforts to independently reproduce these studies. This manuscript describes the isolation of six living strains of halophilic Archaea from cretaceous (121 MYA) salt crystals. This manuscript presents the first isolation of representatives from two different Archaeal genera in a single event. Significance also lies in the fact that these living Archaea contain 16S rRNA genes whose sequence precisely matches that of fragments of 16S rRNA genes isolated from 20 million year old crystals in a separate study. The data presented show that the organisms that inhabited these hypersaline environments today are still similar to those present 121 million years ago. At 121 million years of age these six live strains represent the oldest Archaea known. Considering the number of ancient samples that have now yielded living microbes or DNA fragments the evidence for long term survival of microbes (at least within halite) is becoming overwhelming. While there are obviously still other trapped microbes to find, it may now be time to begin investigating the implications of these ancient microbes and the mechanisms that foster long term survival.