Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/23/2003
Publication Date: 5/18/2003
Citation: Jahn, C.E., Simon, H.M., Bergerud, L.T., Weimer, P.J., Goodman, R.M. 2003. Cultivation of mesophilic soil crenarchaeota in enrichments from tomato roots. [abstract]. American Society for Microbiology Meeting. p. 446. Interpretive Summary:
Technical Abstract: The perception that archaea occupy only extreme and specialized niches is changing as evidence accumulates demonstrating their diversity and widespread distribution in common environments. Culture-independent studies have led to the recovery of sequences from mesophilic and low-temperature (termed nonthermophilic) members of the division Crenarchaeota from aquatic and terrestrial environments worldwide. Other studies suggest this group contributes as much as 34-50% of the total procaryotic biomass in certain marine environments and up to 16% of procaryotic cells on senescent tomato roots. Results from these studies strongly suggest roles for nonthermophilic crenarchaeota in nutrient cycling in the biosphere. We tested the hypothesis that colonization of plant roots by crenarchaeotes could be exploited for their growth in culture. We used the plant to select for soil microorganisms capable of metabolizing root secretions, and applied methods of enrichment culture that select against most known bacteria. We achieved twenty-fold enrichments (40% of cultured cells) of crenarchaeotes using this approach. Growth of these archaea on root extract occurs heterotrophically, at neutral pH, under aerobic or microaerophilic conditions and in close physical association with other microorganisms. Pair-wise analysis of crenarchaeal sequences recovered from enrichments show high (98.4 - 100%) identity of sequences within and between individual cultures, and to soil and rhizosphere crenarchaeal sequences recovered directly from environmenal samples. This suggests we are enriching for variants of a single population, or one genotype with multiple RNA operons. Together with studies documenting the association of soil crenarchaeotes with the roots of numerous plant species, our results provide further support for their functional significance in root microbial ecosystems. Our culturing strategy also resulted in the detection of previously-uncultured members from several bacterial (Planctomyces, Acidobacterium, and Verrucomicrobia) and eukaryotic (Protista) divisions.