Dataset: Dorado Outcrop basalt DNA sequences
Deployment: AT26-09

Acquisition methods are described in the following publication:
Lee, M.D., Walworth, N.G., Sylvan, J.B., Edwards, K.J., and Orcutt, B.N. 2015. Microbial Communities on Seafloor Basalts at Dorado Outcrop Reflect Level of Alteration and Highlight Global Lithic Clades. Front. Microbiol. doi:10.3389/fmicb.2015.01470

In summary (excerpted from above):
Over the span of December 7–23, 2013, 12 seafloor rock samples (11 basalts and 1 lithified carbonate, hereafter R1–R12) were collected from across Dorado Outcrop while aboard R/V Atlantis during cruise AT26-09 following previously developed protocols. Using the ROV Jason II, samples were collected and those for DNA analysis were placed in either sterile whirl-pak bags or centrifuge tubes and frozen at −80 degrees C. In addition to the basalts, two bottom water samples were collected using a Niskin bottle mounted to an elevator, and 1.25 L were filtered onto 0.2 um pore size polycarbonate Nucleopore filters that were then frozen at −80 degrees C.

DNA Extraction and Sequencing of the 16S rRNA Gene
Frozen rock pieces were crushed in a flame-sterilized impact mortar into sand-sized grains which were then transferred to sterile plastic centrifuge tubes and stored at −80 degrees C until DNA extractions were performed. DNA extractions were carried out with the FastDNA Spin Kit for Soil (MP Biomedicals, Santa Ana, CA, USA) following the manufacturer's specifications. About 0.5 g of crushed material were placed directly into the lysis tubes of the kit, as were the bottom water filters. Protocol blanks were performed with each extraction (no samples or DNA added to lysis tubes) to track the potential for contamination. DNA concentrations were quantified with the Qubit HS dsDNA Assay kit with a Qubit 2.0 Fluorometer (Life Technologies, Carlsbad, CA, USA) according to manufacturer protocols.

DNA extracts from the 12 rock samples (plus one technical replicate from the same sample), one green-colored, potential biofilm sample from R11, two bottom water samples, and four protocol blanks for a total of 20 samples were sent for DNA sequencing by a commercial vendor (Molecular Research LP; MR DNA; Shallowater, TX, USA). Illumina MiSeq paired-end (2 × 300 base pair) tag sequencing was carried out using the Earth Microbiome Project universal primers 515f and 806r, which flank the V4 region of the 16S rRNA gene. Library preparation and sequencing was carried out at the facility. In brief, the 515f/806r PCR primers with 8-base barcodes on the forward primer were used in a PCR reaction with the HotStarTaq Plus Master Mix Kit (QIAGEN:USA, Valencia, CA, USA). Based on their DNA concentrations and molecular weight, multiple samples were pooled together in equal proportions, purified with Ampure XP beads, and then used to prepare the library by following the Illumina TruSeq DNA library preparation protocol.

Sequence Data Analysis
Tag data curation and processing were carried out using mothur v.1.34.4 (Schloss et al., 2009) following the mothur Illumina MiSeq Standard Operating Procedure (Kozich et al., 2013). Refer to Lee et al (2015) for more information including treatment of extraction blanks and OTU filtering.

Clone Library Processing
For the clone library, near full-length contigs were assembled using Geneious v6.1.8 (Kearse et al., 2012). Sequences were oriented and trimmed manually and then screened for chimeras using the online program Decipher version 1.14.4 (Wright et al., 2012). The resulting sequences were used in phylogenetic tree construction and submitted to BLAST (Altschul et al., 1990) to search for nearest cultured neighbors as well as environmental samples.

Accession Numbers
The clone sequences recovered from this project are publicly available through NCBI′s GenBank, accession numbers KT748562–KT748628, and the raw tag data are available through NCBI′s Sequence Read Archive under project accession number SRP063681. Additionally, a fasta-formatted file containing the representative OTU sequences identified is available as a Datasheet 2 in Supplementary Material to Lee et al. (2015).