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README.md

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## Overview
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The package provides an API for generating absolute cell count estimates from
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metagenomic sequencing data that includes synthetic DNA (synDNA) spike-ins.
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The general approach, as outlined in Zaramela et al., is to use counts of
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specific synDNAs present in known masses to fit a linear regression model for
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each sample that predicts the gDNA mass of a sequence based on its counts in
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that sample. These linear models are subsequently applied to the counts of
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microbial genomes in each sample to calculate the mass of each such genome,
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and those masses are then transformed into the number of instances of each
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genome (that is, the approximate cell count of that microbe) in the input gDNA.
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pySynDNA extends this approach by also calculating the approximate cell count
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of each microbe in the input sample material (before gDNA extraction).
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metagenomic shotgun sequencing data that includes synthetic DNA (synDNA) spike-ins by
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implementing and extending the technique of [Zaramela et al](https://pubmed.ncbi.nlm.nih.gov/36317886/).
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The calculation is performed in two parts: first, the known
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spiked-in mass of pooled synDNAs and the known concentrations of each synDNA
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within the pool are used to calculate the mass of each synDNA sequenced from a given sample.
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These mass values are paired with the sequenced counts of each synDNA in the sample, and
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a regression model is fitted to predict mass from counts within that sample
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as shown in the figure below.
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![pySynDNA regression fit workflow](https://raw.githubusercontent.com/biocore/pysyndna/main/docs/absolute_quant_fit_models_workflow.png?raw=true)
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The counts for each microbial genome in the sample are then translated into
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masses via the regression model, and the masses are converted to genome counts
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using genome lengths and Avogadro's number
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(see Zaramela et al [equation 2](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9765022/#FD2)).
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Assuming approximately one genome per cell, the calculated genome counts are
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treated as approximate cell counts. pySynDNA extends this approach further by
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using the known starting mass of each sample to calculate the approximate cell
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counts per gram of each microbe in the input sample material (before gDNA extraction).
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These calculations are outlined in the figure below.
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![pySynDNA OGU cell counts workflow](https://raw.githubusercontent.com/biocore/pysyndna/main/docs/absolute_quant_calc_cell_counts_workflow.png?raw=true)
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## Installation
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To install this package, first clone the repository from GitHub:
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```
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git clone https://github.com/AmandaBirmingham/pysyndna.git
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git clone https://github.com/biocore/pysyndna.git
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```
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Change directory into the new `pysndna` folder and create a

setup.py

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"Quantification of Shotgun Metagenomic Sequencing', "
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"Zaramela et al., mSystems 2022)",
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license='BSD-3-Clause',
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description='Python implementation of the SynDNA algorithm',
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description='Python implementation of absolute cell count estimation algorithm',
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author="Amanda Birmingham",
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author_email="abirmingham@ucsd.edu",
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url='https://github.com/AmandaBirmingham/pysyndna',
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url='https://github.com/biocore/pysyndna',
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packages=find_packages(),
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include_package_data=True,
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package_data={

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