celljanus 0.1.3

CellJanus: Dual-Perspective Deconvolution of Host and Microbial Transcriptomes from FASTQ Data

CellJanus: Dual-Perspective Deconvolution of Host and Microbial Transcriptomes from FASTQ Data

Pipeline

FASTQ ─→ fastp (QC) ─→ Bowtie2 (host alignment) ─→ unmapped reads
                             │                            │
                             ▼                            ▼
                    host_aligned.bam           Kraken2 + Bracken  ─→  plots (PNG/PDF) + CSV tables
                   (gene expression)        (microbial abundance)

Contents

1. Installation
2. Quick Start
3. Real Data
4. CLI Reference
5. Python API
6. Output Structure
7. Citation

---

Installation

Requires Linux / macOS / WSL2. Bioconda packages are not available on native Windows.

# Create conda environment with all dependencies
conda create -n CellJanus -c bioconda -c conda-forge \
    python=3.11 fastp bowtie2 samtools kraken2 bracken

# Install CellJanus
conda activate CellJanus
git clone https://github.com/zhaoqing-wang/CellJanus.git
cd CellJanus
pip install .

# Verify installation
celljanus check

All tools should show ✔ Found. STAR is optional (for future RNA-seq alignment support).

Docker alternative

docker build -t celljanus .
docker run --rm celljanus celljanus check

---

Quick Start

The repository includes test data and pre-built reference databases — run the full pipeline immediately with no downloads required.

conda activate CellJanus
cd CellJanus

celljanus run \
    --read1 testdata/reads_R1.fastq.gz \
    --read2 testdata/reads_R2.fastq.gz \
    --host-index testdata/refs/host_genome/host \
    --kraken2-db testdata/refs/kraken2_testdb \
    --output-dir test_results \
    --threads 4

Test data: 1,000 paired-end reads (600 human, 300 microbial, 100 low-quality).

Results (~4 seconds):

Step	Metric
QC	1,000 → 900 pairs retained (90%), Q20 improved 88% → 98%
Host alignment	66.39% aligned to host genome
Classification	300 reads classified → 3 species detected
Top species	S. aureus 38.7%, K. pneumoniae 31.3%, E. coli 30.0%
Output	8 plots (PNG + PDF), 3 CSV tables, QC reports

Example Output

Pipeline Dashboard
Summarises QC, alignment and classification metrics in a single view.

Abundance Bar Chart	Abundance Donut Chart	Abundance Heatmap
Top species ranked by read count.	Relative proportion of each species.	Log₁₀-scaled heatmap of species abundance.

Run Individual Steps

# QC only
celljanus qc -1 testdata/reads_R1.fastq.gz -2 testdata/reads_R2.fastq.gz -o results/01_qc

# Align to host
celljanus align -1 results/01_qc/reads_R1_qc.fastq.gz \
    -2 results/01_qc/reads_R2_qc.fastq.gz \
    -x testdata/refs/host_genome/host -o results/02_alignment

# Classify microbial reads
celljanus classify -1 results/02_alignment/unmapped_R1.fastq.gz \
    -2 results/02_alignment/unmapped_R2.fastq.gz \
    -d testdata/refs/kraken2_testdb -o results/04_classification

# Generate plots
celljanus visualize -b results/04_classification/bracken_S.txt -o results/05_visualisation

---

Real Data

1. Download reference databases

# Human genome hg38 + Bowtie2 index (~5 GB)
celljanus download hg38 -o ./refs

# Kraken2 standard database (~8 GB)
celljanus download kraken2 -o ./refs --db-name standard_8

2. Run pipeline

celljanus run \
    -1 /path/to/sample_R1.fastq.gz \
    -2 /path/to/sample_R2.fastq.gz \
    -x ./refs/bowtie2_index/GRCh38_noalt_as \
    -d ./refs/standard_8 \
    -o ./results \
    --threads 8

Key Options

Option	Default	Description
-1, --read1	required	R1 FASTQ (or single-end FASTQ)
-2, --read2	—	R2 FASTQ for paired-end
-x, --host-index	required	Bowtie2 index prefix
-d, --kraken2-db	required	Kraken2 database path
-o, --output-dir	celljanus_output	Output directory
-t, --threads	auto (CPUs − 2)	Worker threads
--min-quality	15	Phred quality threshold
--confidence	0.05	Kraken2 confidence
--bracken-level	S	Taxonomic level (D/P/C/O/F/G/S)
--skip-qc	—	Skip QC step
--skip-classify	—	Skip classification
--skip-visualize	—	Skip visualisation

---

CLI Reference

Command	Description
celljanus run	Full pipeline: QC → Align → Classify → Visualize
celljanus qc	Quality control (fastp)
celljanus align	Host alignment + unmapped extraction (Bowtie2)
celljanus extract	Extract unmapped reads from BAM
celljanus classify	Taxonomic classification (Kraken2 + Bracken)
celljanus visualize	Generate abundance plots
celljanus download	Download reference databases
celljanus check	Verify external tool installation

Run celljanus <command> --help for full option details.

---

Python API

from pathlib import Path
from celljanus.config import CellJanusConfig
from celljanus.pipeline import run_pipeline

cfg = CellJanusConfig(
    output_dir=Path("./results"),
    host_index=Path("./refs/bowtie2_index/GRCh38_noalt_as"),
    kraken2_db=Path("./refs/standard_8"),
    threads=8,
)

result = run_pipeline(
    Path("sample_R1.fastq.gz"),
    read2=Path("sample_R2.fastq.gz"),
    cfg=cfg,
)

result.bracken_df          # Species abundance (pandas DataFrame)
result.qc_report.summary() # QC statistics

---

Output Structure

output_dir/
├── 01_qc/                           # Quality control
│   ├── *_qc.fastq.gz               # Trimmed reads
│   ├── *_fastp.json                 # QC metrics
│   └── *_fastp.html                 # Interactive report
├── 02_alignment/                    # Host alignment
│   ├── host_aligned.sorted.bam      # Full alignment
│   ├── host_mapped.sorted.bam       # Host-only reads
│   ├── unmapped_R{1,2}.fastq.gz     # Non-host reads → classification
│   └── host_align_stats.txt         # Alignment statistics
├── 04_classification/               # Microbial classification
│   ├── kraken2_report.txt           # Taxonomic report
│   ├── kraken2_output.txt           # Per-read assignments
│   └── bracken_S.txt                # Species abundance
├── 05_visualisation/plots/          # Figures (PNG + PDF)
│   ├── abundance_bar.*              # Horizontal bar chart
│   ├── abundance_pie.*              # Donut chart
│   ├── abundance_heatmap.*          # Heatmap (log₁₀ scale)
│   └── pipeline_dashboard.*         # Summary dashboard
├── 06_tables/                       # Machine-readable results
│   ├── pipeline_summary.csv         # Per-step metrics
│   ├── species_abundance.csv        # Species × reads × fraction
│   └── output_manifest.csv          # File inventory with sizes
└── celljanus.log                    # Pipeline log

CSV Tables

species_abundance.csv:

name	taxonomy_id	bracken_estimated	fraction_pct
Staphylococcus aureus	1280	116	38.67
Klebsiella pneumoniae	573	94	31.33
Escherichia coli	562	90	30.00

pipeline_summary.csv: one row per metric (Step, Metric, Value) covering QC, alignment, and classification statistics.

---

Performance

Component	Memory	Note
fastp	< 1 GB	Streaming I/O
Bowtie2 + hg38	~3.5 GB	Memory-mapped index
Kraken2 (standard DB)	~8 GB	--memory-mapping flag
Peak total	~12–14 GB	Fits a 32 GB laptop

---

Citation

Wang Z (2026). CellJanus: A Dual-Perspective Tool for Deconvolving Host
Single-Cell and Microbial Transcriptomes. Python package version 0.1.3.
https://github.com/zhaoqing-wang/CellJanus

License

MIT