Southern Ocean Experimental Metatranscriptome to Investigate Micronutrient Colimitation

Study Extent

Sampling

Method steps

1. Three bottles were left as unamended controls, three were amended with 1 nM FeCl3, three were amended with 200 pM cyanocobalamin, and three had 200 pM cyanocobalamin and 1 nM Fe added. Iron concentrations in the cobalamin stock were such that < 6 pM iron was added with 200 pM cobalamin (measured via flow injection). Bottles were placed in an indoor incubator at 0°C, ~45 μmol photons m-2 s-1 of constant light. This level of irradiance is in between levels typical for 3 m depth in open water and under the sea ice, and was selected because the harvested community would have experienced both under ice and open water light regimes in the recent past.
2. For RNA extraction, 1 billion copies of each of two RNA standards were added to each filter (#1, #8 ArrayControl Spots and Spikes, Life Technologies, with polyA tails). RNA was extracted from Sterivex filters using the Trizol reagent manufacturer’s protocol (Life Technologies); Trizol was added to the filter membrane after it had been extracted from the plastic housing on dry ice using a sterile pipe cutter, razor blade, and forceps. 450- 800 ng RNA was obtained per filter. RNAeasy MinElut Cleanup kit was applied (Qiagen) and ribosomal RNA was removed with Ribo-Zero Magnetic kits, employing a mix of plant, bacterial, and human/mouse/rat formulations in a ratio of 2:1:1 (Epicentre).
3. The resulting mRNA enrichment was purified using an Agencourt RNAClean XP kit and 2 ng of rRNA depleted RNA was subjected to amplification and cDNA synthesis using the Ovation RNA-Seq System V2 (NuGEN), which applies both polyA and random hexamer primers. 1 μg of the resulting high quality cDNA pool was fragmented to a mean length of 200 bp. Libraries were constructed using a Truseq RNA Sample Prep kit v2 (IlluminaTM), applying the manufacturer’s protocol from the end-repair step. The libraries were then subjected to paired-end sequencing via Illumina Hiseq.

1. Eukaryota
   common name: Eukaryotes rank: domain
2. Bacteria
   common name: Bacteria rank: domain
3. Archaea
   common name: Archaea rank: domain