BOL: Related items

Converting BLAST output into CSV

Poonam Mahapatra — Mon, 11 Dec 2017 04:17:58 -0600

Suppose we wanted to do something with all this BLAST output. Generally, that’s the case - you want to retrieve all matches, or do a reciprocal BLAST, or something.

As with most programs that run on UNIX, the text output is in some specific format. If the program is popular enough, there will be one or more parsers written for that format – these are just utilities written to help you retrieve whatever information you are interested in from the output.

Let’s conclude this tutorial by converting the BLAST output in out.txt into a spreadsheet format, using a Python script.

First, we need to get the script. We’ll do that using the ‘git’ program:

git clone https://github.com/ngs-docs/ngs-scripts.git /root/ngs-scripts

We’ll discuss ‘git’ more later; for now, just think of it as a way to get ahold of a particular set of files. In this case, we’ve placed the files in /root/ngs-scripts/, and you’re looking to run the script blast/blast-to-csv.py using Python:

python /root/ngs-scripts/blast/blast-to-csv.py out.txt

This outputs a spread-sheet like list of names and e-values. To save this to a file, do:

python /root/ngs-scripts/blast/blast-to-csv.py out.txt > ~out.csv

If you have Excel installed, try double clicking on it.

BLAST+ 2.11.0 release is now available on FTP site !

Jit — Sat, 14 Nov 2020 21:37:53 -0600

BLAST+ 2.11.0 release is now available from our FTP site. The main advance is the ability to provide usage reports to NCBI to help us improve BLAST. This information is limited to the name of the BLAST program, some basic database metadata, a few BLAST parameters, as well the number and total size of your queries. See the Privacy document for more details on the information we collect, how we will use it, and how you can opt-out of reporting.

Another new feature allows threading by query batch in rpsblast/rpstblastn. Enabling this option using -m t provides more efficient searching with large numbers of queries. See release notes for details on more improvements and bug fixes.

Useful Links
------------
NCBI Insights: https://ncbiinsights.ncbi.nlm.nih.gov/2020/11/12/blast-2-11-0/

BLAST FTP: https://go.usa.gov/x7QQ3
Privacy document: https://go.usa.gov/x7QQe
Release notes: https://go.usa.gov/x7Qnv

Basics of BLAST Programs !

BioStar — Fri, 26 Jul 2024 06:04:26 -0500

The Basic Local Alignment Search Tool (BLAST) is a powerful bioinformatics program used to compare an input sequence (such as DNA, RNA, or protein sequences) against a database of sequences to find regions of similarity. Developed by the National Center for Biotechnology Information (NCBI), BLAST is widely used for identifying species, finding functional and evolutionary relationships between sequences, and predicting the function of novel sequences.

Key Features of BLAST:
1. Sequence Comparison: BLAST searches for local alignments between the query sequence and sequences in a database. It identifies regions of similarity, which can help infer functional and evolutionary relationships.

2. Speed and Efficiency: BLAST uses heuristic algorithms, making it faster than exhaustive search methods, suitable for large-scale database searches.

3. Versatility: There are several versions of BLAST for different types of sequence comparisons:
- blastn: Compares a nucleotide query sequence against a nucleotide sequence database.
- blastp: Compares a protein query sequence against a protein sequence database.
- blastx: Compares a nucleotide query sequence translated in all reading frames against a protein sequence database.
- tblastn: Compares a protein query sequence against a nucleotide sequence database translated in all reading frames.
- tblastx: Compares the six-frame translations of a nucleotide query sequence against the six-frame translations of a nucleotide sequence database.

4. Scoring and E-value: BLAST results are scored based on the quality and length of the alignments. The E-value (expect value) indicates the number of alignments one can expect to find by chance, with lower E-values representing more significant matches.

5. Output Formats: BLAST provides results in various formats, including plain text, HTML, XML, and JSON, making it adaptable for different types of analyses and integrations with other tools.

Applications of BLAST:
- Genomic Research: Identifying genes, understanding genetic diversity, and mapping genome sequences.
- Protein Function Prediction: Inferring the function of unknown proteins by comparing them to known protein sequences.
- Evolutionary Studies: Exploring evolutionary relationships between organisms by comparing their genetic material.
- Medical Research: Identifying pathogens, understanding disease mechanisms, and developing treatments by comparing sequences of interest.

Overall, BLAST is an essential tool in bioinformatics, offering a reliable and efficient way to analyze and interpret biological sequence data.

Understanding BLASTn output format 6 !

Rahul Nayak — Wed, 27 Jun 2018 18:38:21 -0500

BLASTn output format 6

BLASTn maps DNA against DNA, for example gene sequences against a reference genome

blastn -query genes.ffn -subject genome.fna -outfmt 6

BLASTn tabular output format 6

Column headers:
qseqid sseqid pident length mismatch gapopen qstart qend sstart send evalue bitscore

1.	qseqid	query (e.g., gene) sequence id
2.	sseqid	subject (e.g., reference genome) sequence id
3.	pident	percentage of identical matches
4.	length	alignment length
5.	mismatch	number of mismatches
6.	gapopen	number of gap openings
7.	qstart	start of alignment in query
8.	qend	end of alignment in query
9.	sstart	start of alignment in subject
10.	send	end of alignment in subject
11.	evalue	expect value
12.	bitscore	bit score

Define your own output format

by adding the option -outfmt, as for example:

-outfmt "6 qseqid sseqid pident qlen length mismatch gapope evalue bitscore"

supported format specifiers are:
qseqid    Query Seq-id
qgi   Query GI
qacc    Query accesion
qaccver   Query accesion.version
qlen    Query sequence length
sseqid    Subject Seq-id
sallseqid All subject Seq-id(s), separated by a ';'
sgi       Subject GI
sallgi    All subject GIs
sacc      Subject accession
saccver   Subject accession.version
sallacc   All subject accessions
slen      Subject sequence length
qstart    Start of alignment in query
qend    End of alignment in query
sstart    Start of alignment in subject
send      End of alignment in subject
qseq      Aligned part of query sequence
sseq      Aligned part of subject sequence
evalue    Expect value
bitscore  Bit score
score   Raw score
length    Alignment length
pident    Percentage of identical matches
nident    Number of identical matches
mismatch  Number of mismatches
positive  Number of positive-scoring matches
gapopen   Number of gap openings
gaps      Total number of gaps
ppos      Percentage of positive-scoring matches
frames    Query and subject frames separated by a '/'
qframe    Query frame
sframe    Subject frame
btop      Blast traceback operations (BTOP)
staxids   Subject Taxonomy ID(s), separated by a ';'
sscinames Subject Scientific Name(s), separated by a ';'
scomnames Subject Common Name(s), separated by a ';'
sblastnames Subject Blast Name(s), separated by a ';'   (in alphabetical order)
sskingdoms  Subject Super Kingdom(s), separated by a ';'     (in alphabetical order)
stitle    Subject Title
salltitles  All Subject Title(s), separated by a '<>'
sstrand   Subject Strand
qcovs   Query Coverage Per Subject
qcovhsp   Query Coverage Per HSP

default values are:
-outfmt "6 qseqid sseqid pident length mismatch gapopen qstart qend sstart send evalue bitscore"

REST API

Neel — Mon, 04 Oct 2021 12:46:40 -0500

REST API

The Representational State Transfer (REST) sample clients are provided for a number of programming languages. For details of how to use these clients, download the client and run the program without any arguments.

Language	Download	Requirements
Perl	psiblast.pl	LWP and XML::Simple
Python	psiblast.py	xmltramp2

For details see Environment setup for REST Web Services and Examples for Perl REST Web Services Clients pages.

BEAP: Blast Extension and Assembly Program

Shruti Paniwala — Mon, 11 Jun 2018 04:52:56 -0500

The Blast Extension and Assembly Program (BEAP) is a computer program that uses a short starting DNA fragment, often a EST or partial gene segment, as "primer", to recursively blast nucleotide databases in an attempt to obtain all sequences that overlaps, directly or indirectly, with the "primer" therefore help to "extend" the length of the original sequence for constructing a "full length" sequence for functional analysis, or at least to obtain neighboring regions of the segment for SNP discovery and linkage disequilibrium analysis. The confidence of assembling the resulting sequences is achieved by using a known genome, such as human genome, as a reference. https://www.animalgenome.org/tools/beap/

Address of the bookmark: https://www.animalgenome.org/tools/beap/

List of popular bioinformatics software/tools

Jitendra Narayan — Tue, 16 Jul 2013 14:30:30 -0500

In current genome era, our day to day work is to handle the huge geneome sequences, expression data, several other datasets. This link provide a comprehensive list of commonly used sofware/tools.

Address of the bookmark: http://samtools.sourceforge.net/swlist.shtml

Ensembl comparative genomics resources

Jitendra Narayan — Sun, 28 Feb 2016 17:10:20 -0600

The Ensembl comparative genomics resources are one such reference set that facilitates comprehensive and reproducible analysis of chordate genome data. Ensembl computes pairwise and multiple whole-genome alignments from which large-scale synteny, per-base conservation scores and constrained elements are obtained. Gene alignments are used to define Ensembl Protein Families, GeneTrees and homologies for both protein-coding and non-coding RNA genes. These resources are updated frequently and have a consistent informatics infrastructure and data presentation across all supported species. Specialized web-based visualizations are also available including synteny displays, collapsible gene tree plots, a gene family locator and different alignment views. The Ensembl comparative genomics infrastructure is extensively reused for the analysis of non-vertebrate species by other projects including Ensembl Genomes and Gramene and much of the information here is relevant to these projects. The consistency of the annotation across species and the focus on vertebrates makes Ensembl an ideal system to perform and support vertebrate comparative genomic analyses. We use robust software and pipelines to produce reference comparative data and make it freely available.

Database URL: http://www.ensembl.org.

Address of the bookmark: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4761110/

Ensembl 27

Jit — Tue, 16 Jun 2015 16:10:36 -0500

What is new?

Expansion of Protists and Fungi with hundreds of annotated genomes
Variation data for bread wheat, rice, Aedes aegypti, and Ixodes scapularis
Whole genome alignments for O. longistaminata and T. cacao
Non-coding RNA gene models in Bacteria
New assembly of tomato (version 2.50)
Full support for UCSC Track Hub format for hosting your own data in Ensembl

More at http://www.ensembl.info/blog/2015/06/16/ensembl-genomes-release-27-is-out/