Distribution, Abundance, and Diversity Patterns of the Thermoacidophilic “Deep-Sea Hydrothermal Vent Euryarchaeota 2”

Gilberto E Flores,Anna-Louise Reysenbach,Isaac D Wagner,Yitai Liu

doi:10.3389/fmicb.2012.00047

Abstract

Cultivation-independent studies have shown that taxa belonging to the “deep-sea hydrothermal vent euryarchaeota 2” (DHVE2) lineage are widespread at deep-sea hydrothermal vents. While this lineage appears to be a common and important member of the microbial community at vent environments, relatively little is known about their overall distribution and phylogenetic diversity. In this study, we examined the distribution, relative abundance, co-occurrence patterns, and phylogenetic diversity of cultivable thermoacidophilic DHVE2 in deposits from globally distributed vent fields. Results of quantitative polymerase chain reaction assays with primers specific for the DHVE2 and Archaea demonstrate the ubiquity of the DHVE2 at deep-sea vents and suggest that they are significant members of the archaeal communities of established vent deposit communities. Local similarity analysis of pyrosequencing data revealed that the distribution of the DHVE2 was positively correlated with 10 other Euryarchaeota phylotypes and negatively correlated with mostly Crenarchaeota phylotypes. Targeted cultivation efforts resulted in the isolation of 12 axenic strains from six different vent fields, expanding the cultivable diversity of this lineage to vents along the East Pacific Rise and Mid-Atlantic Ridge. Eleven of these isolates shared greater than 97% 16S rRNA gene sequence similarity with one another and the only described isolate of the DHVE2, Aciduliprofundum boonei T469T. Sequencing and phylogenetic analysis of five protein-coding loci, atpA, EF-2, radA, rpoB, and secY, revealed clustering of isolates according to geographic region of isolation. Overall, this study increases our understanding of the distribution, abundance, and phylogenetic diversity of the DHVE2.

Highlights

The diversity of Archaea associated with marine hydrothermal vent habitats is unrivaled in any other ecosystem on Earth (Auguet et al, 2009)
Deposits from Tui Malila along the ELSC had, on average, the lowest archaeal copy number [8.35 × 104 copies/g (w/w)] while TAG along the Mid-Atlantic Ridge (MAR) had the highest archaeal copy number [9.78 × 107 copies/g (w/w); Table 2]. These values cover a wide range, they are similar to archaeal abundances that have been reported from other hydrothermal vent deposits (Takai et al, 2001; Schrenk et al, 2003; Nakagawa et al, 2005; Zhou et al, 2009)
The DHVE2 were most frequently observed at Mariner (80% of samples), EPR (77.8%), and TAG (75%)

Summary

Introduction

The diversity of Archaea associated with marine hydrothermal vent habitats is unrivaled in any other ecosystem on Earth (Auguet et al, 2009) Much of this diversity resides within the Euryarchaeota where numerous cultivated and uncultivated lineages appear to be endemic to the deep-sea. Our knowledge of the distribution and diversity of the DHVE2 was based primarily on cultivationindependent assessments (Table A1 in Appendix). These studies established that the DHVE2 are widespread in marine hydrothermal environments and can account for up to 15% of the archaeal 16S rRNA gene sequences, suggesting that they are important members of deep-sea hydrothermal ecosystems (Reysenbach et al, 2006). 16S rRNA gene cloning studies have shown that certain types of deep-sea vent mineral deposits, namely horizontal flanges (shelf-like structures that form in some hydrothermal systems, Figure 1, Tivey, 2007), can harbor an even greater proportion of DHVE2 16S rRNA gene sequences (Nunoura and Takai, 2009)

Methods

Results

Conclusion