--- name: bio-basecalling description: Convert raw Nanopore signal data (FAST5/POD5) to nucleotide sequences using Dorado basecaller. Covers model selection, GPU acceleration, modified base detection, and quality filtering. Use when processing raw Nanopore data before alignment. Note: Guppy is deprecated; use Dorado for all new analyses. tool_type: cli primary_tool: dorado --- # Nanopore Basecalling Convert raw electrical signal from Nanopore sequencing into nucleotide sequences. ## Dorado (Recommended) Dorado is ONT's current production basecaller, replacing Guppy. It offers better accuracy and speed. ### Basic Basecalling ```bash dorado basecaller sup pod5_dir/ > calls.bam ``` ### Choose Model ```bash dorado basecaller fast pod5_dir/ > calls.bam dorado basecaller hac pod5_dir/ > calls.bam dorado basecaller sup pod5_dir/ > calls.bam ``` ### Model Speed vs Accuracy | Model | Speed | Accuracy | Use Case | |-------|-------|----------|----------| | fast | Fastest | Lower | Quick preview | | hac | Medium | High | General use | | sup | Slowest | Highest | Publication quality | ### Specific Model Version ```bash dorado download --model dna_r10.4.1_e8.2_400bps_sup@v5.1.0 dorado basecaller dna_r10.4.1_e8.2_400bps_sup@v5.1.0 pod5_dir/ > calls.bam ``` ### List Available Models ```bash dorado download --list ``` ### Output FASTQ Instead of BAM ```bash dorado basecaller sup pod5_dir/ --emit-fastq > calls.fastq ``` ### Modified Base Detection ```bash dorado basecaller sup,5mCG_5hmCG pod5_dir/ > calls_mods.bam dorado basecaller sup,5mCG pod5_dir/ > calls_5mc.bam dorado basecaller sup,6mA pod5_dir/ > calls_6ma.bam ``` ### GPU Selection ```bash dorado basecaller sup pod5_dir/ --device cuda:0 > calls.bam dorado basecaller sup pod5_dir/ --device cuda:0,1 > calls.bam dorado basecaller sup pod5_dir/ --device cpu > calls.bam ``` ### Batch Size for Memory ```bash dorado basecaller sup pod5_dir/ --batchsize 64 > calls.bam ``` ### Duplex Calling ```bash dorado duplex sup pod5_dir/ > duplex.bam ``` ### Demultiplexing During Basecalling ```bash dorado basecaller sup pod5_dir/ --kit-name SQK-NBD114-24 > calls.bam dorado demux calls.bam --output-dir demuxed/ --kit-name SQK-NBD114-24 ``` ### Trim Adapters ```bash dorado basecaller sup pod5_dir/ --trim adapters > calls.bam dorado basecaller sup pod5_dir/ --no-trim > calls_untrimmed.bam ``` ### Resume Interrupted Run ```bash dorado basecaller sup pod5_dir/ --resume-from calls.bam > calls_complete.bam ``` ## Guppy (Deprecated - Legacy Only) Guppy is deprecated and no longer receiving updates. Use Dorado for all new analyses. Guppy examples below are only for maintaining legacy pipelines. ### Basic Basecalling ```bash guppy_basecaller \ -i fast5_dir/ \ -s output_dir/ \ -c dna_r10.4.1_e8.2_400bps_sup.cfg \ --device cuda:0 ``` ### CPU Mode ```bash guppy_basecaller \ -i fast5_dir/ \ -s output_dir/ \ -c dna_r10.4.1_e8.2_400bps_fast.cfg \ --num_callers 8 \ --cpu_threads_per_caller 4 ``` ### High Accuracy Model ```bash guppy_basecaller \ -i fast5_dir/ \ -s output_dir/ \ -c dna_r10.4.1_e8.2_400bps_hac.cfg \ --device cuda:0 ``` ### Super Accuracy Model ```bash guppy_basecaller \ -i fast5_dir/ \ -s output_dir/ \ -c dna_r10.4.1_e8.2_400bps_sup.cfg \ --device cuda:0 ``` ### List Available Configs ```bash guppy_basecaller --print_workflows ls /opt/ont/guppy/data/*.cfg ``` ### Modified Base Calling ```bash guppy_basecaller \ -i fast5_dir/ \ -s output_dir/ \ -c dna_r10.4.1_e8.2_400bps_modbases_5mc_cg_sup.cfg \ --device cuda:0 ``` ### Barcoding During Basecalling ```bash guppy_basecaller \ -i fast5_dir/ \ -s output_dir/ \ -c dna_r10.4.1_e8.2_400bps_sup.cfg \ --device cuda:0 \ --barcode_kits SQK-NBD114-24 ``` ### Output BAM ```bash guppy_basecaller \ -i fast5_dir/ \ -s output_dir/ \ -c dna_r10.4.1_e8.2_400bps_sup.cfg \ --device cuda:0 \ --bam_out \ --index ``` ## POD5 File Handling POD5 is the new format replacing FAST5. ### Convert FAST5 to POD5 ```bash pod5 convert fast5 fast5_dir/*.fast5 --output pod5_dir/ ``` ### Merge POD5 Files ```bash pod5 merge pod5_dir/*.pod5 --output merged.pod5 ``` ### Inspect POD5 ```bash pod5 inspect reads input.pod5 pod5 inspect summary input.pod5 ``` ### Subset POD5 ```bash pod5 subset input.pod5 --output subset.pod5 --read-id-file read_ids.txt ``` ## Quality Filtering ### Filter with Chopper (After Basecalling) ```bash gunzip -c calls.fastq.gz | chopper -q 10 -l 500 | gzip > filtered.fastq.gz ``` ### Filter by Quality Score ```bash gunzip -c calls.fastq.gz | \ awk 'BEGIN{OFS="\n"} {h=$0; getline seq; getline plus; getline qual; split(h, a, " "); split(a[4], q, "="); if(q[2] >= 10) print h, seq, plus, qual}' | \ gzip > q10_filtered.fastq.gz ``` ### NanoFilt (Alternative) ```bash gunzip -c calls.fastq.gz | NanoFilt -q 10 -l 500 | gzip > filtered.fastq.gz ``` ## Basecalling QC ### NanoPlot ```bash NanoPlot --fastq calls.fastq.gz -o qc_report/ --plots hex dot NanoPlot --bam calls.bam -o qc_report/ ``` ### pycoQC (From Sequencing Summary) ```bash pycoQC -f sequencing_summary.txt -o pycoqc_report.html ``` ### Basic Stats ```bash seqkit stats calls.fastq.gz awk 'NR%4==2 {sum+=length($0); count++} END {print "Reads:", count, "Mean length:", sum/count}' calls.fastq ``` ## Model Selection Guide ### R10.4.1 Chemistry (Current) | Model | Use | |-------|-----| | dna_r10.4.1_e8.2_400bps_fast | Quick analysis | | dna_r10.4.1_e8.2_400bps_hac | Routine work | | dna_r10.4.1_e8.2_400bps_sup | High accuracy | ### R9.4.1 Chemistry (Legacy) | Model | Use | |-------|-----| | dna_r9.4.1_450bps_fast | Quick analysis | | dna_r9.4.1_450bps_hac | Routine work | | dna_r9.4.1_450bps_sup | High accuracy | ## Complete Pipeline ```bash #!/bin/bash INPUT=$1 OUTPUT=$2 MODEL=${3:-sup} mkdir -p $OUTPUT if [ -d "$INPUT/fast5" ]; then echo "Converting FAST5 to POD5..." pod5 convert fast5 $INPUT/fast5/*.fast5 --output $OUTPUT/pod5/ INPUT_DIR="$OUTPUT/pod5" else INPUT_DIR="$INPUT" fi echo "Basecalling with $MODEL model..." dorado basecaller $MODEL $INPUT_DIR > $OUTPUT/calls.bam echo "Converting to FASTQ..." samtools fastq $OUTPUT/calls.bam | gzip > $OUTPUT/calls.fastq.gz echo "Filtering..." gunzip -c $OUTPUT/calls.fastq.gz | chopper -q 10 -l 500 | gzip > $OUTPUT/filtered.fastq.gz echo "QC report..." NanoPlot --fastq $OUTPUT/filtered.fastq.gz -o $OUTPUT/qc/ echo "Done!" ``` ## GPU Requirements | Model | VRAM Required | Speed (R10.4.1) | |-------|--------------|-----------------| | fast | 4 GB | ~450 bases/s | | hac | 8 GB | ~200 bases/s | | sup | 12 GB | ~50 bases/s | ## Troubleshooting ### Out of Memory ```bash dorado basecaller sup pod5_dir/ --batchsize 32 > calls.bam ``` ### Slow CPU Basecalling ```bash dorado basecaller fast pod5_dir/ --device cpu > calls.bam ``` ### Check GPU Usage ```bash nvidia-smi -l 1 watch -n 1 nvidia-smi ``` ## Related Skills - long-read-alignment - Align basecalled reads - long-read-qc - QC after basecalling - medaka-polishing - Polish using basecalled reads - structural-variants - SV detection from long reads