PRJNA416333
Temperature controls crystalline iron(III) oxide utilization by microbial communities in ferruginous marine sediment incubations
e carried out Incubation experiments with deep ferruginous sediments from the Helgoland Mud Area, German Bight of the North Sea. Samples were collected using a gravity corer (5 m core length) during RV HEINCKE research expedition HE 443 (54° 05.23'' N; 007° 58.04'' E) in May 2015. In the laboratory, these sediments were stored under anoxic conditions at 4 oC until slurry incubations were. Anoxic 50-mL slurry incubations were made in 120-ml serum vials with sediment from 416 – 441 and 441 – 466 cm depths and anoxic sulphate-free artificial sea water (ASW; composition [L-1]: 26.4 g NaCl, 11.2 g MgCl2.6H2O, 1.5 g CaCl2.2H2O and 0.7 g KCl) at a ratio of 1:3 (w/v) under a headspace of N2. Incubations (n=9) were supplemented by adding iron(III) oxides (hematite or magnetite; LanXess, Germany; 30 µmol l-1) and glucose (2 mM) as electron donor. Control incubations (“glucose only”, n = 9) were supplemented with 2 mM glucose only. The potential for reduction of amended hematite (HG) or magnetite (MG) was evaluated by comparing the amount of Fe2+ formed in crystalline iron(III)-treated incubations to those of the “glucose only” control (G). Triplicates of each treatment set were incubated statically in the dark at 4 oC, 10 oC, or 30 oC. Supplementary incubations were set up at 30 oC, for testing the effect of 2-bromoethanesulfonate (BES) on methanogenesis and iron reduction in the presence of crystalline iron oxides. For molecular analysis, one millilitre of slurry from individual incubations, at specific time points as stated in each sample description, was used for nucleic acid extraction following a modified protocol from Lueders et al (2004). A two-step PCR approach for Illumina amplicon sequencing described by Herbold et al (2015) was adopted for amplification of Bacteria and Archaea 16S rRNA genes. Amplicon library was sequenced using the Miseq Illumina sequencing platform at University of Bremen, Germany. Sequence analysis of forward reads was performed on the QIIME 1.8.0 platform (Caporaso et al., 2010) based on the 16S rRNA gene profiling analysis pipeline recommended by Pylro et al (2014) with modifications. A Total Sum Scaling approach was used to identify dominant members of the microbial communities in each sample. The resulting article written on the project reported relative abundance of 16S rRNA sequences of Bacteria and Archaea that dominated the microbial communities in each sample.