Purushottam (he/him)

Assistant Professor, Yale BME. Previously at University of Florida (Assistant Professor), Columbia (postdoc), and Johns Hopkins University (PhD)

[Purushottam (he/him) @pddixit]

@slavov_n A systems-type answer: Degradation is needed in integral feedbacks and perfect adaptation. This allows Weber-Fechner type relative sensing. We recently worked this out for chemosensing: https://t.co/oJLyOJTsjp

[Purushottam (he/him) @pddixit]

@harriswangnyc @Columbia @ColumbiaMed @ColumbiaSysBio congrats Harris!

[Purushottam (he/him) @pddixit]

Big picture: Directional sensing can be a receptor-level computation driven by diffusion + degradation + feedback. This explains puzzling experiments (e.g., why blocking endocytosis impairs chemotaxis) and suggests a general biophysical strategy across receptors families.

[Purushottam (he/him) @pddixit]

How do cells know which way to move in a chemical gradient? 🧭 New work by graduate student Andrew Goetz proposes that receptors can compute direction. This new mechanism for directional sensing was published in PNAS late last year: https://t.co/oJLyOJU08X

[Purushottam (he/him) @pddixit]

The stochastic analysis is especially striking: Noise reveals an optimal basal activity set point that maximizes signal-to-noise. Too little activity → noisy. Too much → less directional contrast. Biology tunes itself in between.

[Purushottam (he/him) @pddixit]

This low-dimensional structure means that microbial communities are not random spin glasses. They’re shaped by biophysical constraints and environmental trade-offs, echoing the same principles that organize large-scale ecosystems.

[Purushottam (he/him) @pddixit]

This is the second manuscript from our group this week, in collaboration with @platyias. How many dimensions does microbial life really need? 🌎🦠In our new paper “Niche dimensionality drives microbial community structure”, we estimate niche dimensionality of microbiomes.
👇

[bioRxiv Ecology @biorxiv_ecology]

Niche dimensionality drives microbial community structure https://t.co/5HZS4SkNYi #biorxiv_ecology

[Purushottam (he/him) @pddixit]

We found that across hundreds of gut microbiomes, ηᴰ is surprisingly small, just a handful of latent dimensions explain most of community structure, just like low-dimensional food webs in macroecology.

[Purushottam (he/him) @pddixit]

Given the centralization of information flow, our analysis suggests that re-tuning just a few TFs could in principle rejuvenate information flow and restore gene expression. Aging may not be just cellular damage, but a gradual communication breakdown.

[Purushottam (he/him) @pddixit]

What if aging isn’t just cellular damage, but a lossy transmission of information?
We used single-cell data and physics-based models to show that as cells age, the flow of transcriptional information collapses. Here’s what that means. 👇

[bioRxiv SysBio @biorxiv_sysbio]

Decay in transcriptional information flow is a hallmark of cellular aging https://t.co/grtR2nenrs #biorxiv_sysbio

[Purushottam (he/him) @pddixit]

While signs of cellular aging may be varied, across all tissues, mutual information between TFs and TGs declines with age. Aged networks show input mismatch, higher centralization, and reduced stability, patterns reminiscent of aging brains and failing ecosystems.