M. tuberculosis infection in an iPSC-derived macrophage, intracellular Mtb population doubling times highlighted with green outlines time-lapse · z-projected

Nathan J. Day, PhD

Postdoctoral Research Fellow  ·  The Francis Crick Institute  ·  London

I build computational tools to understand how Mycobacterium tuberculosis exploits host cell heterogeneity. My work sits at the intersection of live-cell time-lapse microscopy, deep learning image analysis, and quantitative cell biology — using single-cell tracking to ask why some infected macrophages clear bacteria while others succumb.

In Numbers

macrohet Mtb infection heterogeneity · iPSC-derived macrophages · Crick Institute
0 macrophages
tracked
0 infected cells
analysed
0 cells manually
annotated
0 terabytes of
image data

signatures of competition K-function analysis of cell competition · UCL
0 mitotic events
identified
0 elimination events
manually verified
0 timelapse
acquisitions
0 terabytes of
image data

Education

2018 — 2023
PhD in Cellular Biophysics
University College London  ·  University of London
2013 — 2017
MSci in Physics
King's College London  ·  University of London

Research

host–pathogen interactions single-cell heterogeneity live-cell timelapse microscopy deep learning segmentation cell tracking iPSC-derived macrophages tuberculosis antibiotic efficacy Python image analysis napari
2022 —
Postdoctoral Research Fellow
Gutierrez Lab · The Francis Crick Institute, London

Characterising single-cell heterogeneity of M. tuberculosis infection in iPSC-derived human macrophages using high-throughput time-lapse microscopy. Deep learning segmentation and Bayesian tracking pipeline to trace bacterial burden dynamics at single-cell resolution across antitubercular drug treatments. Pipeline infrastructure built on Dask and OME-NGFF, designed for accessibility and integration with cloud-native, AI-ready approaches.

2018 — 2022
PhD in Cellular Biophysics
Lowe Lab · University College London

Reverse-engineering cell competition from single-cell observations using timelapse microscopy with deep learning segmentation and Bayesian tracking. Characterised mutant elimination dynamics in wild-type vs. ScrKD and RasV12 MDCK epithelium. This work was conducted on a bespoke automated epifluorescence microscope, the design and maintenance of which formed a core part of my doctoral training.

2017
Visiting Researcher
Krieg Lab · Institute of Photonic Sciences, Barcelona

Implementing protein retention expansion microscopy (ProExM) on C. elegans touch receptor neurons.

2016 — 2017
MSci Project — Immunological Signalling & Quantitative Super-Resolution Microscopy
Owen Lab · King's College London

Study of polarity-sensitive fluorescent dyes to probe membrane order in the T-cell immunological synapse, in conjunction with novel super-resolution image analysis techniques.

2015 — 2016
BSc Project — Simulation of Condensed Matter
De Vita Lab · King's College London

An investigation into the self-assembly of borazine-derivative monolayers using Metropolis Monte Carlo algorithms.

Publications

preprint
In Submission
Fast-growing intracellular Mycobacterium tuberculosis populations evade antibiotic treatment.
Day, N. J., Pradel, B., Luk, C. H., Fearns, A., Rodgers, A., Santucci, P., Aylan, B., Botella, L., Vaubourgeix, J., Canseco, J. O., Athanasiadi, N., & Gutierrez, M. G.
Interactive preprint ↗
2026
Autologous human iPSC-derived alveolus-on-chip reveals early pathological events of Mycobacterium tuberculosis infection.
Luk, C. H., Conway, G. L., Goh, K. J., Fearns, A., Rodriguez Hernandez, I., Day, N. J., Athanasiadi, N., D'Antuono, R., Pellegrino, E., Stucki, J. D., Hobi, N., & Gutierrez, M. G.
Science Advances · 12(1), eaea9874 ★ journal cover
doi ↗
2025
Spatial and temporal signatures of cell competition revealed by K-function analysis.
Day, N. J., Michalowska, J., Kelkar, M., Vallardi, G., Charras, G., & Lowe, A. R.
Molecular Biology of the Cell · 36(5) ★ journal cover
doi ↗
2023
Host cell environments and antibiotic efficacy in tuberculosis.
Day, N. J., Santucci, P., & Gutierrez, M. G.
Trends in Microbiology · 32(3), 270–279 ★ journal cover
doi ↗
2022
Convolutional neural networks for classifying chromatin morphology in live-cell imaging.
Ulicna, K., Ho, L., Soelistyo, C., Day, N. J., & Lowe, A. R.
Methods in Molecular Biology · 2476, 17–30
doi ↗
2018
Membrane lipid order of sub-synaptic T cell vesicles correlates with their dynamics and function.
Ashdown, G., Williamson, D., Soh, G., Day, N. J., & Owen, D.
Traffic · 2018; 19: 29–35
doi ↗

Covers & Featured Images

Molecular Biology of the Cell
2025
Manuscript Cover · Vol. 36(5)
Trends in Microbiology cover 2023
Trends in Microbiology
2023
Manuscript Cover · Vol. 32(3)
Artwork by Noémie Matthey
The Francis Crick Institute
2025
Images of Science Exhibition · Gallery Feature

Software

2026
macrohet & macrohet_worldwide
Python framework for high-throughput analysis of intracellular M. tuberculosis growth heterogeneity from multidimensional microscopy data, with an interactive data-sharing web application.
Python napari deep learning tracking
github ↗    live site ↗
2026
Work in Progress
heterognosis
In-development pipeline linking live-cell timelapse tracking with 4i (iterative indirect immunofluorescence imaging) multiplexing, being integrated into a Nextflow pipeline with the Software Engineering and AI STP.
Python Nextflow 4i multiplexing
github ↗
2025
homuncu_loc
Single-cell segmentation and tracking pipeline designed for the autologous human iPSC-derived alveolus-on-a-chip project.
Python segmentation tracking iPSC
github ↗
2024
Cask
Cell competition analysis tool utilising spatiotemporal K-functions to characterise elimination dynamics.
Python K-function cell competition
github ↗
2023
tessell8er
Lightweight Python package for lazy, out-of-core stitching of Opera Phenix image tiles into a single Dask array. Computation is deferred until explicitly triggered, keeping memory usage minimal regardless of mosaic size.
Python Dask Shapely HCS
github ↗
2022
Contributor
btrack
Contributed Dask array support, multi-channel region properties, and Z-dimension segmentation scaling to this Bayesian multi-object tracking framework.
Python Bayesian tracking Dask
github ↗
2021
cnn-annotator
Published protocol repository for annotating microscopy images to train convolutional neural network classifiers for chromatin morphology states.
Python CNN annotation
github ↗
2020
cell-comp-analysis
Core analysis scripts and pipelines developed for PhD research on cell competition, including single-cell feature extraction and spatiotemporal statistics.
Python cell competition analysis
github ↗
2019
jspim_realignment
ImageJ/Fiji macro pipelines for automated compiling and spatial deskewing of multidimensional light-sheet microscopy (SPIM) datasets.
ImageJ Fiji light-sheet SPIM
github ↗
2018
hologram_analysis
MATLAB pipelines for extracting optical path difference and calculating cellular dry mass from Mach-Zehnder interferometry data to study early-stage fate commitment in cell competition.
MATLAB interferometry dry mass
github ↗

Presentations & Posters

01 / 2026
Fast-growing intracellular Mycobacterium tuberculosis populations evade antibiotic treatment
  • Acid Fast Club Winter Meeting, Queen Mary University of London
2025
Poster
Fast-growing intracellular Mycobacterium tuberculosis populations evade antibiotic treatment
  • Crick Bioimage Analysis Symposium, London
  • Host-Pathogen Interactions Mini Symposium, The Francis Crick Institute, London
  • Light Sheet Microscopy EMBO Practical Course, Dresden, Germany
2024 — 2025
Invited Talk ×2
Characterising the single-cell heterogeneity of antibiotic efficacy in Tuberculosis
  • Host-Pathogen Interest Group, The Francis Crick Institute, London
2023 — 2025
Invited Talk ×2
Crash course in object tracking & Intro to Dask lazy-loading
  • Image Analysis Club, The Francis Crick Institute, London
01 / 2022
Invited Talk
How does cell competition play out on a single-cell level?
  • Istanbul Medipol University Canlılık Symposium
01 / 2022
Invited Talk
Deducing the mechanism of cell competition from single-cell observations
  • UCL Bioimage Analysis Interest Group
11 / 2021
Prize-winning Poster
Cell Competition, who makes the first move?
  • Crick Bioimage Analysis Symposium, London

Teaching & Tutoring

2023 — 2024
Mentor — Crick Data Challenge
The Francis Crick Institute, London

Mentored two teams during the annual Crick Data Challenge, guiding early-career researchers through Python-based image analysis and quantitative microscopy workflows.

05 / 2023
Guest Lecturer — LMCB Tutorial on Single-Cell Image Analysis
Laboratory for Molecular Cell Biology, UCL

Delivered lecture for postgraduate students on single-cell image analysis methods.

2021 — 2022
Teaching Assistant — BIOC0016 & CELL0009/CELL0011
University College London

Helped design and deliver MSc-level courses in Computational and Systems Biology and Integrative Cell Biology, focusing on image analysis and machine learning methods.

2014 — 2018
Academic Tutor
Private & classroom settings

Tutored mathematics, biology, chemistry, and physics from school child to graduate level, including private tuition and A-level classrooms.

Public Engagement & Philanthropy

03 / 2025
Invited Presentation — Private Philanthropy Event
The Francis Crick Institute, London

Invited to present research on M. tuberculosis infection heterogeneity to visiting philanthropic donors.

11 / 2023
Curious About the Crick — Philanthropy Evening
The Francis Crick Institute, London

Ran a public engagement stall at a philanthropy evening for prospective supporters of the Francis Crick Institute.

2022 —
Lunch with a Scientist — School Outreach
The Francis Crick Institute, London

Hosted visiting school students at the Crick, introducing young people to life as a researcher and the science of infectious disease.

2022 —
Secondary School Visit — School Outreach

Participating in outreach at my former secondary school to encourage higher education progression — particularly meaningful as a first-generation university student.

2021 — 2022
Volunteer — Euston Food Bank
London

Weekly volunteering throughout the pandemic and beyond, managing stock, coordinating large deliveries, and preparing food packages.

Contact