Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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RNA-seq of iron-rich pelagic aggregates (iron snow) in 2017 and 2018

ABSTRACT: Iron-rich pelagic aggregates (iron snow) were collected directly onto silicate glass filters using an electronic water pump installed below the redoxcline. RNA was extracted and library preparation was done using the NEBNext Ultra II directional RNA library prep kit for Illumina. Data was demultiplied by GATC sequencing company and adaptor was trimmed by Trimgalore. After trimming, data was processed quality control by sickle and mRNA/rRNA sequences were sorted by SortmeRNA. mRNA sequences were blast against NCBI-non redundant protein database and the outputs were meganized in MEGAN to do functional analysis. rRNA sequences were further sorted against bacterial/archeal 16S rRNA, eukaryotic 18S rRNA and 10,000 rRNA sequences of bacterial 16S rRNA, eukaryotic 18S rRNA were subset to do taxonomy analysis.

INSTRUMENT(S): Illumina HiSeq 2000

ORGANISM(S): mixed culture metagenome

SUBMITTER: Qianqian Li

PROVIDER: E-MTAB-9686 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Pelagic aggregates function as hotspots for microbial activity and biological carbon pumps for exporting OM fixed by photoautotrophs to sediments in lakes and oceans. In iron-rich (ferruginous) lakes, photoferrotrophic or chemolithoautotrophic bacteria appear to contribute to CO2 fixation by oxidizing reduced iron which leads to the formation of iron-rich pelagic aggregates called iron-snow. In acidic lakes, iron snow is colonized mainly by acidophilic iron-cycling microbes that can trigger interspecies aggregation mechanisms. However, the significance of iron oxidizers in carbon fixation, their general role in iron snow functioning, and the flow of carbon within iron snow is still unclear. Here, we combined a two-year metatranscriptome analysis with a 13CO2 metabolic labeling approach to determine general metabolic activities. Protein-based stable isotope probing (protein-SIP) was used to trace the 13CO2 incorporation in iron snow microcosms over time under both oxic and anoxic conditions. Analysis of our mRNA-derived metatranscriptome data identified four key players (Leptospirillum, Ferrovum, Acidithrix, Acidiphilium) with relative abundances (59.6%-85.7%) in iron snow encoding a variety of ecologically relevant pathways, including carbon fixation, polysaccharide biosynthesis, and flagellar-based motility. We did not detect transcriptional activity for carbon fixation from archaea or eukaryotes. The largest numbers of expressed genes (3008, 2991, 2936) matched to the genomes of our previously obtained iron snow isolates (Acidithrix sp. C25, Acidiphilium sp. C61, Acidocella sp. C78) separately. 13CO2 incorporation studies identified Leptospirillum and Ferrovum, as the main active chemolithoautotrophs under oxic conditions, and Ferrovum was the main active organism under anoxic conditions as well. Small amounts of labeled 13C (Relative isotope abundance: 1.0%-5.3%) were found in the heterotrophic Acidiphilium and Acidocella. Overall, our data show that iron oxidizers play an important role in the formation of iron minerals and CO2 fixation, but the majority of fixed C apparently did not reach other iron snow microbes. This finding suggests that most of the fixed C will be directly exported to the sediment without feeding heterotrophs in the water column in acidic ferruginous lakes.

Project description:Gene expression along the crypt-villus (C-V) axis was analyzed using cryostat sectioning to isolate fractions representing the crypts (bottom) and villus tops (top). These fractions were used for analyzing gene expression in iron replete Wistar rats (++), iron deficient Wistar rats (low iron), and in iron deficient Wistar rats fed iron for 3 and 6 days (iron-fed). Differences were observed between the crypts and villus tops in the expression of genes associated with Wnt and BNP signaling, cell proliferation and apoptosis, lipid and iron transport and metabolism. Gene expression in villus crypts and tops was also compared between Wistar and Belgrade rats (bb) and Belgrade rats fed iron (iron-fed) particularly as related to iron absorption and metabolism to define the affects of the mutation in DMT1 in the Belgrade rat on the expression of genes related to iron absorption and metabolism and the response to iron feeding. Keywords: iron stress response A colony of Wistar strain rats (++) and Belgrade (bb) rats on a Wistar background maintained in our animal quarters was used for this study. Twelve one-month old ++ rats were separated into 3 groups of four rats each. Group 1 rats (samples 1-8) were fed a normal diet and served as control animals. Group 2 (samples 9-16) and Group 3 rats (samples 17-22) were fed a low iron diet and bled 2-3 ml every three days for 4 weeks and served as iron deficient rats (low-iron). Group 3 rats, of which one rat died during anesthesia while undergoing phlebotomy, were fed iron supplementation in drinking water (50 ÂµM Ferric ammonium citrate) for the three days before sacrifice (iron-fed). Rats were fasted overnight, killed by injection of pentobarbital sodium and a 1-cm duodenal segment 1 cm distal from the pylorus was cryostat sectioned at the right angle to the crypt-villus axis and the sections representing the top one-third of villus (top) and the bottom one-third of the villus were pooled for RNA isolation. For the study of Belgrade rats, eleven bb rats were divided into 3 groups with the 4 rats in Group 1 (samples 23-30) maintained on a normal diet, the 4 rats in Group 2 (samples 31-38) fed iron for 3 days prior to sacrifice, and the 3 rats in Group 3 (samples 39-44) fed iron for 6 days prior to sacrifice. All procedures for the bb rats were the same as described above for the ++ rats. An additional ++ rat (samples 45-46) was similarly analyzed in a separate experiment.

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RNA-seq of iron-rich pelagic aggregates (iron snow) in 2017 and 2018

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