eplace 0.1.1

ePLACE: environmental Phylogenetic Localisation and Clade Estimation - A library for analyzing eDNA sequences

eplace

ePLACE: environmental Phylogenetic Localisation and Clade Estimation

A Python library for analyzing environmental DNA (eDNA) sequences through BLAST comparison and taxonomic classification.

Features

• NCBI Database Management: Download and manage NCBI BLAST databases (core_nt)
• FASTA File Processing: Read and validate FASTA files
• BLAST Search: Run blastn searches with configurable parameters
• Result Filtering: Filter BLAST results by identity and coverage thresholds
• Taxonomic Analysis: Extract representative sequences per taxonomic rank
• Sequence Extraction: Retrieve sequences from BLAST databases
• Sequence Trimming: Trim reference sequences to aligned regions based on BLAST coordinates
• Multiple Sequence Alignment: Align sequences using MAFFT with auto-orientation
• Phylogenetic Trees: Build and label phylogenetic trees using IQTree
• Results Summary Output: Creates a tab separated output that summarises the per-sequence matches.

Installation

# Clone the repository
git clone https://github.com/linsalrob/eplace.git
cd eplace

# Install the package
pip install .

# Or install in development mode
pip install -e .

# Or with development dependencies
pip install -e ".[dev]"

After installation, the eplace command will be available in your environment.

Requirements

• Python 3.8 or higher
• BLAST+ tools (blastn, blastdbcmd) must be installed separately:

  # Ubuntu/Debian
  sudo apt-get install ncbi-blast+
  
  # macOS with Homebrew
  brew install blast
  

• TaxonKit (for taxonomy lookup):

  # Download from: https://github.com/shenwei356/taxonkit/releases
  # Or install via conda:
  conda install -c bioconda taxonkit
  

• MAFFT (optional, for sequence alignment):

  # Ubuntu/Debian
  sudo apt-get install mafft
  
  # macOS with Homebrew
  brew install mafft
  
  # Or via conda:
  conda install -c bioconda mafft
  

• IQTree (optional, for phylogenetic tree building):

  # Ubuntu/Debian
  sudo apt-get install iqtree
  
  # macOS with Homebrew
  brew install iqtree
  
  # Or via conda:
  conda install -c bioconda iqtree
  

Quick Start

ePLACE provides a unified command-line interface with three main commands:

1. Download NCBI Database

# Download the core_nt database to default location
eplace download

# Force redownload even if database exists
eplace download --force

2. Run Individual BLAST Analysis

Run BLAST search and build one phylogenetic tree per query sequence:

# Basic usage with default parameters
eplace blast query.fasta output_dir

# With custom parameters
eplace blast query.fasta output_dir \
    --rank genus \
    --min-identity 95 \
    --min-coverage 85 \
    --num-threads 4

# Skip alignment and tree building (BLAST and extraction only)
eplace blast query.fasta output_dir --skip-alignment

# Show help
eplace blast --help

3. Run Grouped BLAST Analysis

Run BLAST search and group queries by taxonomic rank for joint phylogenetic analysis:

# Basic usage (group by class, default)
eplace grouped query.fasta output_dir

# Group by different taxonomic rank
eplace grouped query.fasta output_dir --group-rank order

# Specify both representative and grouping ranks
eplace grouped query.fasta output_dir --rank genus --group-rank family

# Show help
eplace grouped --help

Using the Library API

You can also use ePLACE as a Python library:

from eplace_lib import setup_ncbi_database

# Download the core_nt database
success, message = setup_ncbi_database()

from pathlib import Path
from eplace_lib import run_blast_search, process_blast_results_for_taxonomy

# Run BLAST search with filtering
success, filtered_hits = run_blast_search(
    query_fasta=Path("query.fasta"),
    output_file=Path("blast_results.txt"),
    min_identity=90.0,    # 90% identity threshold
    min_coverage=80.0     # 80% query coverage threshold
)

# Extract representative sequences by taxonomic rank
results = process_blast_results_for_taxonomy(
    blast_hits=filtered_hits,
    output_dir=Path("output"),
    rank="species"  # Options: phylum, class, order, family, genus, species
)

Command-Line Interface

The eplace command provides three subcommands:

eplace download

Download and setup the NCBI core_nt BLAST database.

Usage:

eplace download [--force]

Options:

• --force: Force redownload even if database exists

Notes:

• Database will be stored in $BLASTDB if set, otherwise ~/blastdb
• The download is large (several GB) and may take time
• MD5 checksums are verified automatically

eplace blast

Run BLAST search with individual taxonomy analysis. Creates one phylogenetic tree per query sequence.

Usage:

eplace blast QUERY_FASTA OUTPUT_DIR [OPTIONS]

Required Arguments:

• QUERY_FASTA: Path to query FASTA file
• OUTPUT_DIR: Output directory for results

Optional Arguments:

• --rank {phylum,class,order,family,genus,species}: Taxonomic rank for representative selection (default: genus)
• --tree-label-rank {phylum,class,order,family,genus,species}: Taxonomic rank for tree labeling (default: genus)
• --min-identity FLOAT: Minimum percent identity for BLAST hits (default: 90.0)
• --min-coverage FLOAT: Minimum query coverage percentage (default: 80.0)
• --database NAME: BLAST database name (default: core_nt)
• --blastdb-path PATH: Path to BLAST database directory
• --num-threads INT: Number of threads for BLAST and alignment (default: 1)
• --overwrite-existing-blast: Overwrite existing BLAST results
• --skip-alignment: Skip alignment and tree building steps
• --output-classification PATH: Path to output classification TSV file

eplace grouped

Run BLAST search with grouped taxonomy analysis. Groups queries by taxonomic rank and creates one phylogenetic tree per group.

Usage:

eplace grouped QUERY_FASTA OUTPUT_DIR [OPTIONS]

Required Arguments:

• QUERY_FASTA: Path to query FASTA file
• OUTPUT_DIR: Output directory for results

Optional Arguments:

• --rank {phylum,class,order,family,genus,species}: Taxonomic rank for representative selection (default: genus)
• --group-rank {phylum,class,order,family,genus,species}: Taxonomic rank for grouping sequences (default: class)
• --tree-label-rank {phylum,class,order,family,genus,species}: Taxonomic rank for tree labeling (default: genus)
• --min-identity FLOAT: Minimum percent identity for BLAST hits (default: 90.0)
• --min-coverage FLOAT: Minimum query coverage percentage (default: 80.0)
• --database NAME: BLAST database name (default: core_nt)
• --blastdb-path PATH: Path to BLAST database directory
• --num-threads INT: Number of threads for BLAST and alignment (default: 1)
• --overwrite-existing-blast: Overwrite existing BLAST results
• --skip-alignment: Skip alignment and tree building steps
• --alignment-tolerance INT: Maximum coordinate difference for alignment consistency (default: 50)
• --output-classification PATH: Path to output classification TSV file

Documentation

Full documentation is available at Read the Docs.

• Installation Guide - Complete installation instructions
• Quick Start Guide - Get started quickly
• Command-Line Interface - Complete CLI reference
• Workflows - Individual and grouped workflow details
• API Reference - Python API documentation
• NCBI Database Download - Database management guide
• BLAST Workflow - BLAST analysis guide
• Alignment - Sequence alignment documentation
• Phylogenetic Trees - Tree building guide
• Contributing - Contribution guidelines

Local Documentation

You can also build the documentation locally:

cd docs
make html
# Open docs/build/html/index.html in your browser

Workflow Comparison

Individual Workflow (eplace blast)

The individual workflow processes each query sequence independently:

• Creates one output directory per query sequence
• Extracts representative sequences for each query at the specified taxonomic rank
• Builds one multiple sequence alignment per query
• Creates one phylogenetic tree per query

Use when: You want to analyze each query sequence in its own phylogenetic context.

Grouped Workflow (eplace grouped)

The grouped workflow combines queries by taxonomic classification:

• Groups all queries that match to the same taxonomic rank (e.g., class, order)
• Creates one FASTA file per group containing all queries and unique reference sequences
• Removes redundant reference sequences within each group
• Builds one alignment and phylogenetic tree per group (instead of per query)

Use when: You want to analyze multiple related queries together in a single phylogenetic context.

Examples

# Group queries by class (default)
eplace grouped query.fasta output_dir

# Group by a different taxonomic rank
eplace grouped query.fasta output_dir --group-rank order

# Specify both representative rank and grouping rank
eplace grouped query.fasta output_dir --rank genus --group-rank family

Testing

Run the test suite:

# Run all tests
pytest tests/ -v

# Run specific test modules
pytest tests/test_blast_analysis.py -v
pytest tests/test_taxonomy.py -v
pytest tests/test_workflow.py -v

# Run with coverage
pytest tests/ --cov=eplace_lib --cov-report=html

Project Structure

eplace/
├── src/
│   └── eplace_lib/
│       ├── __init__.py
│       ├── blast_analysis.py    # BLAST operations
│       ├── ncbi_download.py     # Database management
│       ├── sequences.py         # Sequence analysis utilities
│       └── taxonomy.py          # Taxonomy extraction
├── tests/
│   ├── test_blast_analysis.py
│   ├── test_ncbi_download.py
│   ├── test_taxonomy.py
│   └── test_workflow.py
├── examples/
│   ├── blast_workflow_example.py
│   └── download_ncbi_example.py
├── docs/
│   ├── blast_workflow.md
│   └── ncbi_download.md
└── pyproject.toml

Workflow Overview

1. Download Database: Use setup_ncbi_database() to download NCBI core_nt database
2. Prepare Query: Create a FASTA file with your query sequences
3. Run BLAST: Use run_blast_search() to search against the database
4. Filter Results: Automatically filter by identity and coverage thresholds
5. Extract Representatives: Select representative sequences per taxonomic rank
6. Trim Sequences: Extract aligned regions from reference sequences based on BLAST coordinates
7. Align Sequences: Use MAFFT to align query with trimmed reference sequences (optional)
8. Build Tree: Build phylogenetic tree using IQTree with taxonomic labels (optional)
9. Output: Get FASTA files, alignments, and trees (one set per query)

Grouped Workflow Overview

The grouped workflow adds an additional step: 1-5. Same as standard workflow through representative extraction 6. Group by Rank: Group all queries by specified taxonomic rank (e.g., class) 7. Create Grouped FASTA: Combine all queries and unique references for each group 8. Trim Sequences: Trim references to aligned regions 9. Check Consistency: Verify BLAST hits align to similar locations on references 10. Align and Build Trees: Create one alignment and tree per taxonomic group

Output Structure

Standard Workflow Output

output_dir/
├── blast_results.txt              # Raw BLAST results
├── blast_results_annotated.txt    # BLAST results with taxonomic annotations
├── query1_id/
│   ├── query1_id_representatives.fasta          # Representative sequences
│   ├── query1_id_with_query.fasta              # Query + representatives
│   ├── query1_id_trimmed.fasta                 # Trimmed to aligned regions
│   ├── query1_id_aligned.fasta                 # Multiple sequence alignment
│   ├── query1_id_tree.treefile                 # Phylogenetic tree
│   ├── query1_id_tree_labeled.treefile         # Tree with taxonomic labels
│   └── query1_id_tree.* (other IQTree files)
├── query2_id/
│   └── query2_id_representatives.fasta
└── ...

Grouped Workflow Output

output_dir/
├── blast_results.txt              # Raw BLAST results
├── blast_results_annotated.txt    # BLAST results with taxonomic annotations
├── query1_id/                     # Per-query representative sequences (from step 5)
│   └── query1_id_representatives.fasta
├── query2_id/
│   └── query2_id_representatives.fasta
├── Taxonomic_Group_1/             # One directory per taxonomic group
│   ├── Taxonomic_Group_1_combined.fasta        # All queries + unique references
│   ├── Taxonomic_Group_1_trimmed.fasta         # Trimmed to aligned regions
│   ├── Taxonomic_Group_1_aligned.fasta         # Multiple sequence alignment
│   ├── Taxonomic_Group_1_tree.treefile         # Phylogenetic tree
│   ├── Taxonomic_Group_1_tree_labeled.treefile # Tree with taxonomic labels
│   └── Taxonomic_Group_1_tree.* (other IQTree files)
├── Taxonomic_Group_2/
│   └── ...
└── ...

License

MIT License - See LICENSE file for details

Authors

• Rob Edwards ([e-mail])

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Citation

If you use ePLACE in your research, please cite:

Edwards, R. (2024). ePLACE: environmental Phylogenetic Localisation and Clade Estimation.
GitHub repository: https://github.com/linsalrob/eplace

Support

For issues, questions, or suggestions, please open an issue on GitHub: https://github.com/linsalrob/eplace/issues