contigs-db

A DB-type anvi’o artifact. This artifact is typically generated, used, and/or exported by anvi’o (and not provided by the user)..

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Provided by

anvi-gen-contigs-database

Required or used by

anvi-cluster-contigs anvi-compute-completeness anvi-db-info anvi-delete-functions anvi-delete-hmms anvi-display-contigs-stats anvi-display-metabolism anvi-display-structure anvi-draw-kegg-pathways anvi-estimate-genome-completeness anvi-estimate-metabolism anvi-estimate-scg-taxonomy anvi-estimate-trna-taxonomy anvi-export-contigs anvi-export-functions anvi-export-gene-calls anvi-export-gene-coverage-and-detection anvi-export-locus anvi-export-misc-data anvi-export-splits-and-coverages anvi-export-splits-taxonomy anvi-gen-fixation-index-matrix anvi-gen-gene-consensus-sequences anvi-gen-gene-level-stats-databases anvi-gen-structure-database anvi-gen-variability-profile anvi-get-aa-counts anvi-get-codon-frequencies anvi-get-codon-usage-bias anvi-get-metabolic-model-file anvi-get-pn-ps-ratio anvi-get-sequences-for-gene-calls anvi-get-sequences-for-hmm-hits anvi-get-short-reads-from-bam anvi-get-short-reads-mapping-to-a-gene anvi-get-split-coverages anvi-import-collection anvi-import-functions anvi-import-misc-data anvi-import-taxonomy-for-genes anvi-inspect anvi-interactive anvi-merge anvi-migrate anvi-profile anvi-profile-blitz anvi-reaction-network anvi-refine anvi-rename-bins anvi-run-cazymes anvi-run-hmms anvi-run-interacdome anvi-run-kegg-kofams anvi-run-ncbi-cogs anvi-run-pfams anvi-run-scg-taxonomy anvi-run-trna-taxonomy anvi-scan-trnas anvi-search-functions anvi-search-palindromes anvi-search-sequence-motifs anvi-show-misc-data anvi-split anvi-summarize anvi-summarize-blitz anvi-update-db-description anvi-update-structure-database anvi-script-add-default-collection anvi-script-estimate-metabolic-independence anvi-script-filter-hmm-hits-table anvi-script-gen-distribution-of-genes-in-a-bin anvi-script-gen-genomes-file anvi-script-get-hmm-hits-per-gene-call anvi-script-merge-collections anvi-script-permute-trnaseq-seeds

Description

A contigs database is an anvi’o database that contains key information associated with your sequences.

In a way, an anvi’o contigs database is a modern, more talented form of a FASTA file, where you can store additional information about your sequences in it and others can query and use it. Information storage and access is primarily done by anvi’o programs, however, it can also be done through the command line interface or programmatically.

The information a contigs database contains about its sequences can include the positions of open reading frames, tetra-nucleotide frequencies, functional and taxonomic annotations, information on individual nucleotide or amino acid positions, and more.

Here is a graphic that shows what sort of information goes into the contigs database (and also the profile-db):

Another (less computation-heavy) way of thinking about it

When working in anvi’o, you’ll need to be able to access previous analysis done on a genome or transcriptome. To do this, anvi’o uses tools like contigs databases instead of regular fasta files. So, you’ll want to convert the data that you have into a contigs database to use other anvi’o programs (using anvi-gen-contigs-database). As seen on the page for metagenomes, you can then use this contigs database instead of your fasta file for all of your anvi’o needs.

In short, to get the most out of your data in anvi’o, you’ll want to use your data (which was probably originally in a fasta file) to create both a contigs-db and a profile-db. That way, anvi’o is able to keep track of many different kinds of analysis and you can easily interact with other anvi’o programs.

Usage Information

Creating and populating a contigs database

Contigs databases will be initialized using anvi-gen-contigs-database using a contigs-fasta. This will compute the k-mer frequencies for each contig, soft-split your contigs, and identify open reading frames. To populate a contigs database with more information, you can then run various other programs.

Key programs that populate an anvi’o contigs database with essential information include,

• anvi-run-hmms (which uses HMMs to annotate your genes against an hmm-source)
• anvi-run-scg-taxonomy (which associates its single-copy core gene with taxonomic data)
• anvi-scan-trnas (which identifies the tRNA genes)
• anvi-run-ncbi-cogs (which tries to assign functions to your genes using the COGs database)

Once an anvi’o contigs database is generated and populated with information, it is always a good idea to run anvi-display-contigs-stats to see a numerical summary of its contents.

Other programs you can run to populate a contigs database with functions include,

• anvi-run-kegg-kofams (which annotates the genes in the database with the KEGG KOfam database)

Analysis on a populated contigs database

Other essential programs that read from a contigs database and yield key information include anvi-estimate-genome-completeness, anvi-get-sequences-for-hmm-hits, and anvi-estimate-scg-taxonomy.

If you wish to run programs like anvi-cluster-contigs, anvi-estimate-metabolism, and anvi-gen-gene-level-stats-databases, or view your database with anvi-interactive, you’ll need to first use your contigs database to create a profile-db.

Variants

Contigs databases, like profile-dbs, are allowed have different variants, though the only currently implemented variant, the trnaseq-contigs-db, is for tRNA transcripts from tRNA-seq experiments. The default variant stored for “standard” contigs databases is unknown. Variants should indicate that substantially different information is stored in the database. For instance, open reading frames are applicable to protein-coding genes but not tRNA transcripts, so ORF data is not recorded for the trnaseq variant. The $(trnaseq-workflow)s generates trnaseq-contigs-dbs using a very different approach to anvi-gen-contigs-database.

For power users

Since the anvi’o contigs database is a stand-alone SQLite database, it is accessible to users to perform very complex queries using SQL, or Structured Query Language. You can do it either entering into SQLite command line environment from your terminal by typing,

sqlite3 CONTIGS.db

which would initiate the program to run queries on your contigs database, and welcome you with a new comand prompt in your terminal (you can quit the SQLite terminal to go back to your original terminal anytime by pressing CTRL+D):

SQLite version 3.31.1 2020-01-27 19:55:54
Enter ".help" for usage hints.
sqlite>

In this prompt you can run any query that is a valid SQLite query to learn about the structure and contents of the database. Here is an example, where the table names in the database are listed:

sqlite> .tables
amino_acid_additional_data  hmm_hits_in_splits
collections_bins_info       hmm_hits_info
collections_info            kmer_contigs
collections_of_contigs      kmer_splits
collections_of_splits       nt_position_info
contig_sequences            nucleotide_additional_data
contigs_basic_info          scg_taxonomy
gene_amino_acid_sequences   self
gene_functions              splits_basic_info
genes_in_contigs            splits_taxonomy
genes_in_splits             taxon_names
genes_taxonomy              trna_taxonomy

Another example to see the schema of a given table to learn about the field names:

sqlite> .schema contigs_basic_info
CREATE TABLE contigs_basic_info (contig str, length numeric, gc_content numeric, num_splits numeric);

Another example to see the contents of a given table:

sqlite> select * from self;
db_type|contigs
contigs_db_hash|d51abf0a
split_length|20000
kmer_size|4
num_contigs|4189
total_length|35766167
num_splits|4784
genes_are_called|1
splits_consider_gene_calls|1
creation_date|1466453807.46107
project_name|Infant Gut Contigs from Sharon et al.
description|No description is given
external_gene_calls|0
external_gene_amino_acid_seqs|0
skip_predict_frame|0
trna_taxonomy_was_run|0
trna_taxonomy_database_version|
version|20
modules_db_hash|72700e4db2bc
gene_function_sources|COG20_CATEGORY,KOfam,COG20_PATHWAY,COG14_FUNCTION,KEGG_Module,COG20_FUNCTION,Transfer_RNAs,COG14_CATEGORY,KEGG_Class
scg_taxonomy_was_run|1
scg_taxonomy_database_version|v202.0
gene_level_taxonomy_source|centrifuge

This example shows the contents of the self table, which is a special table that keep track of some meta information about the contigs database itself. If you compare this output to the output you get from the program anvi-db-info, you may feel like you have found a shortcut to see something very core about the philosophy behind anvi’o and how it works.

This environment is extremely powerful to ask complex, creative, or unconventional questions to learn anything you may want to learn about your data, even if anvi’o is not ready to answer those questions for you. Here we can use a question that was asked on anvi’o Discord by an anvi’o user to demonstrate this:

My contigs database includes contigs longer than 500 nts, how can I get summary statistics for my genes (such as the number of gene calls and the number of annotations per function annotation source) but only for contigs that are longer than 10,000 nts?

One anvi’o way to answer this question is the following:

• Create a collection for contigs that are longer than 1000 nts (which would require one to parse a previous summary of the data),
• Create a blank profile-db using anvi-profile,
• Import the collection into the blank profile database using anvi-import-collection,
• Summarize the collection using anvi-summarize,
• Survey the output files to find out how many genes are there in the collection and their annotations (using BASH tools such as grep and wc, or other tools such as EXCEL or R).

But the power of SQL enables a much quicker answer to it. Here are the steps to answer this particular question as an exercise.

Learning the number of genes:

sqlite> select count(*) from genes_in_contigs;
32597

Number of contigs:

sqlite> select count(*) from contigs_basic_info;
4189

Contigs longer than 10000 nts:

sqlite> select count(*) from contigs_basic_info where length > 10000;
658

Number of genes that occur in contigs that are longer than 10000 nts:

sqlite> select count(*) from genes_in_contigs where contig IN (select contig from contigs_basic_info where length > 10000);
22117

Number of function annotations for genes per annotation source:

sqlite> select source, count(*) from gene_functions group by source;
COG14_CATEGORY|21121
COG14_FUNCTION|21121
COG20_CATEGORY|20878
COG20_FUNCTION|20878
COG20_PATHWAY|6088
KEGG_Class|2760
KEGG_Module|2760
KOfam|14391
Transfer_RNAs|323

Number of function annotations per annotation source for genes that occur in contigs that are longer than 10000 nts:

sqlite> select source, count(*) from gene_functions where gene_callers_id IN (select gene_callers_id from genes_in_contigs where contig IN (select contig from contigs_basic_info where length > 10000)) group by source;
COG14_CATEGORY|14472
COG14_FUNCTION|14472
COG20_CATEGORY|14235
COG20_FUNCTION|14235
COG20_PATHWAY|4154
KEGG_Class|2260
KEGG_Module|2260
KOfam|11652
Transfer_RNAs|280

At this point we have the answer to both questions in a few minutes. The power of this is that the same query will work on any computer and any anvi’o contigs-db out there. Thus making it possible to conduct specific yet complex interrogations of any anvi’o project in the wild by simply formatting a query and sending it to collaborators or colleagues.

SQLite queries can be run without having to go into the SQLite terminal, too. For instance, one could run this directly from their terminal,

sqlite3 CONTIGS.db 'select source, count(*) from gene_functions group by source'

which would have resulted in this output in the terminal:

COG14_CATEGORY|21121
COG14_FUNCTION|21121
COG20_CATEGORY|20878
COG20_FUNCTION|20878
COG20_PATHWAY|6088
KEGG_Class|2760
KEGG_Module|2760
KOfam|14391
Transfer_RNAs|323

Or this,

sqlite3 -column -header CONTIGS.db 'select source, count(*) from gene_functions group by source'

to get a slighly fancier output:

source          count(*)
--------------  ----------
COG14_CATEGORY  21121
COG14_FUNCTION  21121
COG20_CATEGORY  20878
COG20_FUNCTION  20878
COG20_PATHWAY   6088
KEGG_Class      2760
KEGG_Module     2760
KOfam           14391
Transfer_RNAs   323

Or this,

sqlite3 -separator $'\t' -header CONTIGS.db 'select source, count(*) from gene_functions group by source' | anvi-script-tabulate

to get an even fancier output,

╒════════════════╤════════════╕
│ source         │   count(*) │
╞════════════════╪════════════╡
│ COG14_CATEGORY │      21121 │
├────────────────┼────────────┤
│ COG14_FUNCTION │      21121 │
├────────────────┼────────────┤
│ COG20_CATEGORY │      20878 │
├────────────────┼────────────┤
│ COG20_FUNCTION │      20878 │
├────────────────┼────────────┤
│ COG20_PATHWAY  │       6088 │
├────────────────┼────────────┤
│ KEGG_Class     │       2760 │
├────────────────┼────────────┤
│ KEGG_Module    │       2760 │
├────────────────┼────────────┤
│ KOfam          │      14391 │
├────────────────┼────────────┤
│ Transfer_RNAs  │        323 │
╘════════════════╧════════════╛

Or this,

sqlite3 -separator $'\t' -header CONTIGS.db 'select source, count(*) from gene_functions group by source' | anvi-script-as-markdown

To get an output that can be pasted to markdown-aware editors such as GitHub, so the output would look like this:

Learning SQL is not difficult, and one can practice their skills using their existing anvi’o databases. When there is a specific question, forming a meaningful SQL query takes only minutes. If you are not sure where to start or how to form an SQL query, you can always reach out to the community at the anvi’o Discord.

For programmers

It is also possible to use anvi’o as a Python library to work with anvi’o artifacts, including contigs-db. The purpose of this section is to list tips and use cases for programmers, and it is extended by questions we have received from the community. If you have a problem you wish to solve programmatically, but not sure how, please reach out to the community via anvi’o Discord or anvi’o GitHub.

Get approximate number of genomes

You can estimate the number of genomes once anvi-run-hmms is run on an contigs database.

Here are some examples of how to do this programmatically (more info on how the estimates are calculated can be found here):

from anvio.hmmops import NumGenomesEstimator

# the raw data, where each key is one of the HMM collections
# of type `singlecopy` run on the contigs-db
NumGenomesEstimator('CONTIGS.db').estimates_dict
>>> {'Bacteria_71': {'num_genomes': 9, 'domain': 'bacteria'},
     'Archaea_76': {'num_genomes': 1, 'domain': 'archaea'},
     'Protista_83': {'num_genomes': 1, 'domain': 'eukarya'}}

# slightly fancier output with a single integer for
# estimated number of genomes summarized, along with
# domains used
num_genomes, domains_included = NumGenomesEstimator('CONTIGS.db').num_genomes()
print(num_genomes)
>>> 11

print(domains_included)
>>> ['bacteria', 'archaea', 'eukarya']

# limiting the domains
num_genomes, domains_included = NumGenomesEstimator('CONTIGS.db').num_genomes(for_domains=['archaea', 'eukarya'])
print(num_genomes)
>>> 2

print(domains_included)
>>> ['archaea', 'eukarya']

Edit this file to update this information.