Kabir Husain
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kabirhusain.bsky.social
Kabir Husain
@kabirhusain.bsky.social
Physics | Molecular Biology | Evolution.
Lecturer at UCL Physics.

Formerly:
Postdoc with @amurugan.bsky.social at the University of Chicago.
PhD with Madan Rao and Jitu Mayor at NCBS, Bangalore.
Reposted by Kabir Husain
Center for Living Systems -- seeking strong post docs at the interface of physics and biology. Consider applying by Oct. 13! docs.google.com/forms/d/e/1F...
docs.google.com
September 4, 2025 at 2:06 AM
Reposted by Kabir Husain
How common are frequency dependent fitness effects?

New preprint out today 👇
doi.org/10.1101/2025...
Frequency-dependent fitness effects are ubiquitous
In simple microbial populations, the fitness effects of most selected mutations are generally taken to be constant, independent of genotype frequency. This assumption underpins predictions about evolutionary dynamics, epistatic interactions, and the maintenance of genetic diversity in populations. Here, we systematically test this assumption using beneficial mutations from early generations of the Escherichia coli Long-Term Evolution Experiment (LTEE). Using flow cytometry-based competition assays, we find that frequency-dependent fitness effects are the norm rather than the exception, occurring in approximately 80\% of strain pairs tested. Most competitions exhibit negative frequency-dependence, where fitness advantages decline as mutant frequency increases. Furthermore, we demonstrate that the strength of frequency-dependence is predictable from invasion fitness measurements, with invasion fitness explaining approximately half of the biological variation in frequency-dependent slopes. Additionally, we observe violations of fitness transitivity in several strain combinations, indicating that competitive relationships cannot always be predicted from fitness relative to a single reference strain alone. Through high-resolution measurements of within-growth cycle dynamics, we show that simple resource competition explains a substantial portion of the frequency-dependence: when faster-growing genotypes dominate populations, they deplete shared resources more rapidly, reducing the time available for fitness differences to accumulate. Our results demonstrate that even in a simple model system designed to minimize ecological complexity, subtle ecological interactions between closely related genotypes create frequency-dependent selection that can fundamentally alter evolutionary dynamics. ### Competing Interest Statement The authors have declared no competing interest.
doi.org
August 21, 2025 at 7:23 PM
Reposted by Kabir Husain
Excited to share our latest by my postdoc Ben KS: we use statistical physics & Bayesian inference to model genome-wide perturbation outcomes. Remarkably, perturbation responses are encoded in gene "chatter" even before the perturbation–a fundamental insight with broad implications
shorturl.at/2LHbw
July 6, 2025 at 10:11 PM
Reposted by Kabir Husain
February 27, 2025 at 7:48 PM
Reposted by Kabir Husain
When did synovial joints evolve? @neelimasharma.bsky.social @neilshubin.bsky.social &co reveal that stable, mobile & lubricated joints were present in the common ancestor of jawed fishes but lacking in jawless ones 🧪 @plosbiology.org plos.io/3CTC8La
February 25, 2025 at 7:09 PM
Reposted by Kabir Husain
Interested in a PhD in Physics of Life Theory? Applications for the EMBL PhD program are still open until March 10!
embl.org EMBL @embl.org · Feb 20
EMBL International PhD Programme - summer recruitment 2025! 👀

Research groups across EMBL are recruiting now! www.embl.org/about/info/e...

Don’t miss this opportunity to receive dedicated mentoring while doing interdisciplinary research.

🧪#AcademicSky #MolBiol #PhDSky #careers @ebi.embl.org
February 22, 2025 at 9:50 AM
Reposted by Kabir Husain
Our interdisciplinary MRes is recruiting students for Sept 2025 entry : www.ucl.ac.uk/lifesciences...
MRes Computational Cell Biophysics
At the forefront of interdisciplinary research
www.ucl.ac.uk
November 17, 2024 at 9:32 PM
Reposted by Kabir Husain
Listen to Professor Jonathan Chubb talking about slime moulds, the brainless organisms that can find their way around a maze, on BBC Radio 4's In Our Time at 9am this morning (02/01/25). www.bbc.co.uk/programmes/m...
January 2, 2025 at 8:12 AM
Not one, but two PhD opportunities with a fantastic group in a brilliant scientific environment (and a great city!). Come be our colleague!
Come work with me! Two fully-funded PhD positions in Theoretical Physics of Living Matter are available in my group at UCL, in the wonderful city of London . For more information and to apply, visit www.agudo-canalejo.com/work-with-us
December 19, 2024 at 4:35 AM
This is phenomenally elegant
Get ready to dance, our paper – Phage DisCo: targeted discovery of bacteriophages by co-culture – has been pre-printed! 🪩 This has been a really fun project to work on with @sianowen.bsky.social, @baym.lol, @nquinoneso.bsky.social, and our two talented undergrads Kesther and Carmen!
Phage DisCo: targeted discovery of bacteriophages by co-culture https://www.biorxiv.org/content/10.1101/2024.11.22.624878v1
November 23, 2024 at 11:12 PM
Reposted by Kabir Husain
This is a really important perspective on microbial ecology/evolution (Balakrishnan & Cremer). Quantitative physiology shows that microbes do not optimize growth, but instead express unutilized proteins that confer distinct dynamics when environments change.

www.sciencedirect.com/science/arti...
Conditionally unutilized proteins and their profound effects on growth and adaptation across microbial species
Protein synthesis is an important determinant of microbial growth and response that demands a high amount of metabolic and biosynthetic resources. Des…
www.sciencedirect.com
October 25, 2024 at 2:36 AM
Reposted by Kabir Husain
From Ben Good: competition btwn linked mutations can..enhance selection for modifiers that increase benefits of future mutations, even when they impose a strong direct cost on fitness. However..modest direct benefits can..drive evolutionary dead ends to fixation. www.nature.com/articles/s41...
Evolution of evolvability in rapidly adapting populations - Nature Ecology & Evolution
Evolvability modifier mutations alter the rates and benefits of future mutations, but it is difficult to predict when they will be favoured by natural selection. A mathematical framework shows that co...
www.nature.com
September 17, 2024 at 4:47 PM
Pleased as punch to note, for my first post, that I just submitted a grant with the killer acronym of HiDenSeq (say it out loud...)

...and it's got an assay we called BALDy!

Surely the panel will weight names as much as scientific content in their decision, right?
October 20, 2024 at 10:45 PM
Reposted by Kabir Husain
Interested in studying Computational Cell Biophysics at UCL? Applications are open for our innovative MRes programme at the interface between physics and biology! ucl.ac.uk/lmcb/mres-ccb
Watch this video to find out more:
mediacentral.ucl.ac.uk/Player/9h335dB3
February 6, 2024 at 9:56 PM