01-get-NCBI-sequences

Environment pre-reqs:

• sequence data files deposited on NCBI
• code and commentary written in Quarto
• operating within RStudio on a Unix OS (Roberts Lab raven server)
• file structure:
  • code
  • data
  • output

Install Packages

Code

if ("tidyverse" %in% rownames(installed.packages()) == 'FALSE') install.packages('tidyverse')
if ("SRAdb" %in% rownames(installed.packages()) == 'FALSE') BiocManager::install("SRAdb")

Load packages

Code

library(SRAdb)
library(tidyverse)

Get sample metadata

First we want to get an idea of the files we are downloading and the samples that generated the data. We will start by looking at the metadata for the samples.

Code

# navigate to data directory
cd ../data

# download metadata from the git repo into the data directory
curl -O https://raw.githubusercontent.com/AHuffmyer/EarlyLifeHistory_Energetics/master/Mcap2020/Data/TagSeq/Sample_Info.csv  

Code

#pull data into R and rename it metadata 
metadata <- read_csv("../data/Sample_Info.csv")

Check file integrity with md5sum

Info

Learn How to Generate and Verify Files with MD5 Checksum in Linux

Code

cd ../data
md5sum Sample_Info.csv > md5.transferred

Code

cd ../data
cmp Sample_Info.csv md5.transferred

These files differ by 1 byte, and I haven’t yet figured out why… possibly a windows vs unix thing

Code

#look at the metadata
head(metadata)

There are 39 samples (rows) with 8 metadata columns in this tibble dataset (AH1 - AH39). These samples are Montipora capitata coral taken at different life-stages (denoted by column names time-stage and code ), and RNA extracted and sequenced using Tag-Seq.

M. capitata development diagram by A. Huffmyer

Get TagSeq FASTQ files from National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA)

Info

Checkout some background info on The Sequence Read Archive (SRA) and the SRA factsheet

NCBI sequences have been trimmed and cleaned and are ready for alignment and analysis.

Use SRA Run Selector to make a .txt file list of Run (SRR) numbers

“Results are called runs (SRR). Runs comprise the data gathered for a sample or sample bundle and refer to a defining experiment.”

First, we need to obtain RNAseq files from NCBI from the project PRJNA900235. In order to do this we need a list of SRR numbers that identify the specific sequence files for RNA. Go to the SRA Run Selector for BioProject 900235 and select the files of interest.

To make things easier and faster, we’re going to compare 2 life-history groups, with an n=4 for each group. In this case, let’s compare 4 Embryos (an early stage) to 4 Attached Recruits (a later stage).

SRA run selector, downloading 8 fastq files (4 Embryo, 4 Attached Recruits)

Select the files of interest, click ‘Accession List’ and the list of file run ID’s will be downloaded in a text file named SRR_Acc_list.txt , upload this list into the data folder.

Navigate to or create the directory where you will download the fastq files

Code

# move to large data hard-drive 
cd /home/shared/8TB_HDD_01
# make a new directory named 'mcap', short for Montipora capitata
mkdir mcap

Download the fastq files

Roberts Lab Resources Github issue#1569 thread

Using sratoolkit.3.0.2-ubuntu64 which is already downloaded in /home/shared folder

Danger

The following code will take some time, run it and go take a wee break

Code

/home/shared/sratoolkit.3.0.2-ubuntu64/bin/./fasterq-dump \
--outdir /home/shared/8TB_HDD_01/mcap \
--progress \
SRR22293447 \
SRR22293448 \
SRR22293449 \
SRR22293450 \
SRR22293451 \
SRR22293452 \
SRR22293453 \
SRR22293454

Absolute path to fastq files in raven:

/home/shared/8TB_HDD_01/mcap/

Relative path to fastq files in raven:

cd ../../../../../8TB_HDD_01/mcap/

Check that the fastq files are downloaded:

Code

cd /home/shared/8TB_HDD_01/mcap/
ls

Tip

The fastq files have been downloaded from NCBI!