Detection and Phylogenetic Relationships of Highly Diverse Uncultured Acidobacterial Communities in Altamira Cave Using 23S rRNA Sequence Analyses

Acidobacteria have been established as a novel and widespread bacterial phylum consistently detected during 16S rDNA-based molecular surveys. Recently, representatives of the phylum Acidobacteria were found to make up a large percentage of cloned sequences recovered from paleolithic paintings. The present study addresses the intraphylum diversity of Acidobacteria in Altamira Cave. In contrast to previous studies, we have focused on 23S rRNA-based phylogenetic analyses, exploiting the high information content of the 23S RNA gene. Comparison with existing studies was facilitated by the preparation of corresponding 16S rRNA clone libraries. Fourty-one distinct operational taxonomic units (OTU) could be identified. Of the eight described acidobacterial subgroups, five were represented in the cave; only subgroups 1, 2, and 8 were not found. Subgroup 4 was the group harbouring the highest number of OTUs. Various clusters that could not be assigned to any of the established subgroups, but were clearly grouped within the phylum and appeared to represent new taxa at elevated phylogenetic levels, were detected. Results from this study give a first insight into the enormous acidobacterial diversity existing in a single hypogean environment containing unique paleolithic paintings, the Altamira Cave. Novel taxa have been found within the phylum, suggesting a higher diversity of Acidobacteria than previously suspected even at a local scale.

Keywords:

• Acidobacteria
• Altamira Cave
• paleolithic paintings
• 23S rRNA
• phylogeny
• 16S rRNA

The authors wish to thank the Spanish Ministry of Culture (Contract 31321000710T, “Analysis of the conditions for the conservation of paleolithic paintings in Altamira Cave”) and the Spanish Ministry of Education and Science (Project BTE 2002-04492-C02-01 and REN 2003-02854/GLO). J.Z. is grateful to the Marie Curie programme (EKV4-CT2000-56130). J. M. G. is thankful for the support provided by the Ramon y Cajal Programme from the Spanish Ministry of Education and Science. The authors wish to thank Dr. Adrian Pearce for helpful comments on the manuscript.

Notes

¹Zimmermann J. 2002. PhD thesis. ⟨http://tumb1.biblio.tu-muenchen.de/publ/diss/ch/2002/zimmermann.html⟩

² Brosius et al. (1981).

¹For amplification types, see Table 2.

²Newly proposed subgroups are represented in bold.