Soil microbiome (Bacteria) on Keller Peninsula (Antarctica)

Study Extent

Sampling

Method steps

1. DNA was isolated from at least 1 g of mixed soil using the PowerSoilTM DNA Isolation Kit (MO BIO) as described by the manufacturer. The genomic DNA concentration and purity were determined by spectrophotometry.
2. Twelve independent PCR reactions were performed for each soil sample with the primers 338R and 27F for the amplification of the V1–V2 hypervariable regions of the 16S rRNA gene. PCR was performed with the GoTaq PCR core system (Promega, Madi- son, WI, USA). The mixtures contained 5 ul of 10× PCR buffer, 200 mM dNTPs, 100 mM of each primer, 2.5 U of Taq polymerase and approximately 100ng of DNA template in a final volume of 50 ul. The PCR conditions were 94 ◦ C for 2 min, 30 cycles of 94◦C for 45s; 55◦C for 45s; and 72◦C for 1min extension; followed by 72 ◦C for 6 min. The 16S rRNA gene fragments were sequenced using 454 GS FLX Titanium (Lib-L) chemistry for unidirectional sequencing of the amplicon libraries. Barcoded primers were used to multiplex the amplicon pools so they could be sequenced together and computationally separated afterward. To do this, 8-base barcodes were added to the 5′-end of the reverse primers using the self-correcting barcode method of Hamady et al. (2008). The primers were attached to the GS FLX Titanium Primer A (5′ -CCATCTCATCCCTGCGTGTCTCCGACTCAG-3′ ) and Primer B (5′ - CCTATCCCCTGTGTGCCTTGGCAGTC-3′ ) sequences, modified for use with GS FLX Titanium emPCR Kits (Lib-L) and a two-base linker sequence was inserted between the 454 adapter and the 16S rRNA primers to reduce any effect the composite primer might have on PCR efficiency. The PCR products for each of the 12 samples were purified and combined in equimolar ratios with the quantitative DNA binding method (SequalPrep Kit, Invitrogen, Carlsbad, CA, USA) to create a DNA pool that was used for pyrosequencing from the A-Key adaptor.

1. Bacteria
   common name: Bacteria rank: domain