Biology subjects

Deb, D.

Publications and source records attributed to Deb, D..

15 recordsLinked to original sources

bioRxiv2026

Phage-assisted continuous evolution of enzymes for noncanonical tyrosine biosynthesis

Genetic code expansion introduces new-to-nature chemical moieties into ribosomally synthesized proteins. In practice, the scope of functional groups that can be accessed using this method is often limited by noncanonical amino acid (ncAA) availability. Producing ncAAs directly in cells can circumvent poor ncAA uptake or commercial unavailability, but limited enzymes suitable for this application exist. In vitro evolution campaigns have been remarkably successful in yielding synthetically useful "ncAA synthases." However, these enzymes are optimized for preparative-scale synthesis and their activities often do not translate well to cellular biosynthesis. Thus, expanding strategies to engineer enzymes specifically for ncAA production within cells will benefit further implementation of genetic code expansion. Here, we use phage-assisted noncontinuous and continuous evolution to evolve enzymes for improved synthesis of non-canonical tyrosine derivatives in E. coli. Using simple serial passaging, we uncovered mutations that doubled the production of an expensive ncAA, 3-methoxytyrosine, by tyrosine phenol lyase, and furthermore evolved variants that enable 3-iodotyrosine biosynthesis, a transformation the parent enzyme is unable to catalyze. Additionally, we evolved a recently reported tyrosine synthase for improved production of 3-halogenated tyrosines, identifying variants that exhibit high activity even at low substrate concentrations owing to a [~]8-fold reduction in KM. Our results demonstrate that phage assisted evolution can be used to rapidly improve the activity of enzymes for ncAA production in cells.

synthetic biology↗

bioRxiv2025

High Cross Pollination Frequency in Rice Landraces in Field Condition

Flower opening time (FOT) and the duration of florets remaining open (= flower exposure duration, FED) are crucially important for successful cross pollination between neighbouring rice plants. When the florets of the ovary parent (or pollen recipient) open even a few seconds after the closure of all the florets of the the pollen parent of a rice cultivar, the chances of cross pollination (CP) would obviously be zero. Conversely, as shown by our previous study, cross pollination frequency (CPF) would be very high (>80%) if the overlap of FEDs of the PP and OP is considerably long. In continuation of our previous study conducted in 2019, we subsequently conducted crossing experiments with 19 pairs of rice landraces during short-day flowering season and 8 pairs during long-day flowering season. The results show that with a long (>20 min) duration of FED overlap between OP and PP, the CPF tends to exceed 60%, often reaching 100%, although in some cases successful CP resulted in variable degrees of F1 sterility. These data confirm our previous report; and contradict the century-old received wisdom based on a series of crossing experiments, that CP in rice rarely exceeds 2%, as widely published in all textbooks and official literature in rice biology. Our experimental evidence show the actuality of naturally high CPF in rice under circumstances of considerable FED overlap between parental cultivars, and indicates the necessity of further exploration into genetic interactions of sterile grain production and assortments of polygenic traits in the offspring from crosses between different varietal genotypes.

plant biology↗

bioRxiv2025

Lifestyle transition from rural to urban setting changes the gut bacterial profile in an ethnic community of northeast India

The human gut microbiome undergoes transformation due to various exogenous and endogenous influences. Lifestyle has been one of the major contributors of gut microbiome composition. Our study investigated the effect of migration on the gut microbiome of the Mishing ethnic community in India associated with urban migration from their pastural lifestyle. Gut bacterial diversity was profiled using 16S rRNA amplicon sequencing. We observed notable alterations in microbial diversity and composition, including changes in the core microbiome. While Bifidobacterium, Lactococcus and Streptococcus significantly increased (p < 0.01) among the migrant population there was depletion in bacteria such as Succinivibrio and Prevotella. This change in core microbiome was further reflected on the functional profile of the bacterial community harbored by the urban and rural dwellers. While the rural population was enriched in fatty acid biosynthesis pathways, amino acid and Vitamin B2 biosynthesis pathways were more prominent in the microbiome of the urban dwellers. We further observed increase in diversity and richness of the microbiome following migration. Co-analysis with ASVs from food samples consumed by the Mishing rural population revealed that 51 ASVs among the rural dwellers were from a widely consumed beverage, Apong which were completely absent among the migrants. Our analyses highlight the dietary preferences, particularly abstinence from specific foods and beverages, may modulate the alterations in gut microbial profiles. While the cross-sectional design and amplicon sequencing limited our ability to assess temporal and functional changes, our findings highlight a measurable impact of lifestyle and dietary transitions on the gut microbiome.

microbiology↗

bioRxiv2025

Chromatix: a differentiable, GPU-accelerated wave-optics library

Modern microscopy methods incorporate computational modeling as an integral part of the imaging process, either to solve inverse problems or optimize the optical system design itself. These methods often depend on differentiable optics simulations, yet no standardized framework exists--forcing computational optics researchers to repeatedly and independently implement simulations with limited reusability and performance. These common problems limit the potential impact of computational optics as a field. Here we present Chromatix: an open-source, GPU-accelerated, differentiable wave optics simulation library. Chromatix builds on JAX to democratize fast, parallelized simulation of diverse optical systems and expand the design space in computational optics. Chromatix standardizes a growing collection of optical elements and propagation methods allowing a broad range of applications, which we demonstrate here for snapshot microscopy, holography, and phase retrieval. We demonstrate speed improvements of 2-6x on a single GPU and up to 22x on 8 GPUs.

bioinformatics↗

bioRxiv2024

Engineered reactivity of a bacterial E1-like enzyme enables ATP-driven modification of protein C termini

In biological systems, ATP provides an energetic driving force for peptide bond formation, but protein chemists lack tools that emulate this strategy. Inspired by the eukaryotic ubiquitination cascade, we developed an ATP-driven platform for C-terminal activation and peptide ligation based on E. coli MccB, a bacterial ancestor of ubiquitin-activating (E1) enzymes that natively catalyzes C-terminal phosphoramidate bond formation. We show that MccB can act on non-native substrates to generate an O-AMPylated electrophile that can react with exogenous nucleophiles to form diverse C-terminal functional groups including thioesters, a versatile class of biological intermediates that have been exploited for protein semisynthesis. To direct this activity towards specific proteins of interest, we developed the Thioesterification C-terminal Handle (TeCH)-tag, a sequence that enables high-yield, ATP-driven protein bioconjugation via a thioester intermediate. By mining the natural diversity of the MccB family, we developed two additional MccB/TeCH-tag pairs that are mutually orthogonal to each other and to the E. coli system, facilitating the synthesis of more complex bioconjugates. Our method mimics the chemical logic of peptide bond synthesis that is widespread in biology for high-yield in vitro manipulation of protein structure with molecular precision.

biochemistry↗

bioRxiv2023

The Effect of Sunlight Intensity on Flower Opening Time and Exposure Duration in Rice (Oryza sativa ssp. indica) Landraces

Records of sunlight intensity at anthesis of 388 rice landraces (with 32 replicated populations), flowering in the short-day season of 2022, reveal that under cloudy condition, the rice florets tend to open later, or the sunrise-to-anthesis duration (SAD) is longer when rice florets open than at sunny period. This difference in the length of SAD was statistically highly significant (p < 0.0001), confirmed by two sample permutation test with 10,000 iterations. This finding corroborates our general observation previously reported from a larger set of 1114 landraces (including the 388 landraces in this study). However, the intensity of sunlight at the flower opening time (FOT) may not remain uniformly sunny (high illuminance) or cloudy (low illuminance, < 40000 lux) until the flower closing time (FCT). To understand the effect of uniformly low sunlight intensity, we subsequently recorded solar illuminance at FOT of 33 landrace populations (including 8 repeats). Half of each population was kept under artificial shade, compared to the other half exposed to sunlight. This experiment revealed that low illuminance, mimicking overcast days, significantly (p < 0.01) delays FOT and lengthens SAD, corroborating the pattern detected in our earlier findings. Permutation tests with 10,000 iterations decisively confirms (p < 0.0001) the prolongation of SAD under shade and cloudy condition. Experimental shading has an indeterminate effect on FED of the same landraces. We surmise that the delayed FOT during natural cloudy period is an adaptation in rice plants in anticipation of rain, for protection of the pollen from rainwash.

plant biology↗

bioRxiv2023

A single dietary factor, daily consumption of a fermented beverage, can modulate the gut microbiome within the same ethnic community

In this study, the impact of traditional rice-based fermented alcoholic beverages (Apong) on the gut microbiome and health of the Mishing community in India was examined. Two groups that consumed one of these beverages were compared to a control group that did not consume either beverage. Gut microbial composition was analyzed by sequencing 16S rRNA of fecal metagenomes and analyzing untargeted fecal metabolites, and short-chain fatty acids (SCFAs). We also collected data on anthropometric measures and serum biochemical markers. Our results showed that Apong drinkers had higher blood pressure, but lower blood glucose and total protein levels than other non-drinkers. Also, gut microbiome composition was found to be affected by the choice of Apong, with Apong drinkers having a more diverse and distinct microbiome compared to non-drinkers. Apong drink type or being a non-drinker explained even a higher variation of fecal metabolome composition than microbiome composition and Apong drinkers had lower levels of the SCFA isovaleric acid than non-drinkers. Overall, this study shows that a single dietary factor can significantly impact the gut microbiome of a community and highlights the potential role of traditional fermented beverages in maintaining gut health.

microbiology↗

bioRxiv2021

Diversification of small RNA pathways underlies germline RNAi incompetence in wild C. elegans strains

The discovery that experimental delivery of dsRNA can induce gene silencing at target genes revolutionized genetics research, by both uncovering essential biological processes and creating new tools for developmental geneticists. However, the efficacy of exogenous RNAi varies dramatically within the C. elegans population, raising questions about our understanding of RNAi in the lab relative to its activity and significance in nature. Here, we investigate why some wild-type strains fail to mount a robust RNAi response to germline targets. We observe diversity in mechanism: in some strains, the response is stochastic, either on or off among individuals, while in others the response is consistent but delayed. Increased activity of the Argonaute PPW-1, which is required for germline RNAi in the laboratory strain N2, rescues the response in some strains, but dampens it further in others. Among wild-type strains, genes known to mediate RNAi exhibited very high expression variation relative to other genes in the genome as well as allelic divergence and strain-specific instances of pseudogenization at the sequence level. Our results demonstrate functional diversification in the small RNA pathways in C. elegans, and suggest that RNAi processes are evolving rapidly and dynamically in nature.

evolutionary biology↗

bioRxiv2021

Local Shape Descriptors for Neuron Segmentation

We present a simple, yet effective, auxiliary learning task for the problem of neuron segmentation in electron microscopy volumes. The auxiliary task consists of the prediction of Local Shape Descriptors (LSDs), which we combine with conventional voxel-wise direct neighbor affinities for neuron boundary detection. The shape descriptors are designed to capture local statistics about the neuron to be segmented, such as diameter, elongation, and direction. On a large study comparing several existing methods across various specimen, imaging techniques, and resolutions, we find that auxiliary learning of LSDs consistently increases segmentation accuracy of affinity-based methods over a range of metrics. Furthermore, the addition of LSDs promotes affinity-based segmentation methods to be on par with the current state of the art for neuron segmentation (Flood-Filling Networks, FFN), while being two orders of magnitudes more efficient--a critical requirement for the processing of future petabyte-sized datasets. Implementations of the new auxiliary learning task, network architectures, training, prediction, and evaluation code, as well as the datasets used in this study are publicly available as a benchmark for future method contributions.

neuroscience↗

bioRxiv2020

From infection to immunity: understanding the response to SARS-CoV2 through in-silico modeling

BackgroundImmune system conditions of the patient is a key factor in COVID-19 infection survival. A growing number of studies have focused on immunological determinants to develop better biomarkers for therapies. AimThe dynamics of the insurgence of immunity is at the core of the both SARS-CoV-2 vaccine development and therapies. This paper addresses a fundamental question in the management of the infection: can we describe the insurgence (and the span) of immunity in COVID-19? The in-silico model developed here answers this question at individual (personalized) and population levels. We simulate the immune response to SARS-CoV-2 and analyze the impact of infecting viral load, affinity to the ACE2 receptor and age in the artificially infected population on the course of the disease. MethodsWe use a stochastic agent-based immune simulation platform to construct a virtual cohort of infected individuals with age-dependent varying degree of immune competence. We use a parameter setting to reproduce known inter-patient variability and general epidemiological statistics. ResultsWe reproduce in-silico a number of clinical observations and we identify critical factors in the statistical evolution of the infection. In particular we evidence the importance of the humoral response over the cytotoxic response and find that the antibody titers measured after day 25 from the infection is a prognostic factor for determining the clinical outcome of the infection. Our modeling framework uses COVID-19 infection to demonstrate the actionable effectiveness of simulating the immune response at individual and population levels. The model developed is able to explain and interpret observed patterns of infection and makes verifiable temporal predictions. Within the limitations imposed by the simulated environment, this work proposes in a quantitative way that the great variability observed in the patient outcomes in real life can be the mere result of subtle variability in the infecting viral load and immune competence in the population. In this work we i) show the power of model predictions, ii) identify the clinical end points that could be more suitable for computational modeling of COVID-19 immune response, iii) define the resolution and amount of data required to empower this class of models for translational medicine purposes and, iv) we exemplify how computational modeling of immune response provides an important view to discuss hypothesis and design new experiments, in particular paving the way to further investigations about the duration of vaccine-elicited immunity especially in the view of the blundering effect of immunesenescence.

bioinformatics↗

bioRxiv2020

Relationship Between Neuroendocrine and Immune Gene Expression in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is classified as a high-grade neuroendocrine (NE) tumor, but a subset of SCLC has been termed "variant" due to the loss of NE characteristics. In this study, we computed NE scores for patient-derived SCLC cell lines and xenografts, as well as human tumors. We aligned NE properties with transcription factor-defined molecular subtypes. Then we investigated the different immune phenotypes associated with high and low NE scores. We found repression of immune response genes as a shared feature between classic SCLC and pulmonary neuroendocrine cells of the healthy lung. With loss of NE fate, variant SCLC tumors regain cell-autonomous immune gene expression and exhibit higher tumor-immune interactions. Pan-cancer analysis revealed this NE lineage-specific immune phenotype in other cancers. Additionally, we observed MHC I re-expression in SCLC upon development of chemoresistance. These findings provide a new framework to guide design of treatment regimens in SCLC.

cancer biology↗

bioRxiv2020

Algorithms underlying flexible phototaxis in larval zebrafish

To thrive, organisms must maintain physiological and environmental variables in optimal ranges. However, in a dynamic world, the optimal range of a variable might fluctuate depending on the organisms state or environmental conditions. Given these fluctuations, how do biological control systems maintain optimal control of physiological and environmental variables? We explored this question by studying the phototactic behavior of larval zebrafish. We demonstrate, with behavioral experiments and computational modeling, that larval zebrafish use phototaxis to maintain environmental luminance at a set point that depends on luminance history. We further show that fish compute this set point using information from both eyes, and that the set point fluctuates on a timescale of seconds when environmental luminance changes. These results expand on previous studies, where phototaxis was found to be primarily positive, and suggest that larval zebrafish, rather than consistently turning towards the brighter areas, exert homeostatic control over the luminance of their surroundings. Furthermore, we show that fluctuations in the surrounding luminance feed back on the system to drive allostatic changes to the luminance set point. Our work has uncovered a novel principle underlying phototaxis in larval zebrafish and characterized a behavioral algorithm by which larval zebrafish exert control over a sensory variable.

neuroscience↗

bioRxiv2019

Broken force dispersal network in tip-links by the mutations induces hearing-loss

Tip-link as force-sensor in the hearing conveys the mechanical force originating from sound to ion-channels while maintaining the integrity of the entire sensory assembly in inner-ear. This delicate balance between structure and function of tip-links is regulated by Ca2+-ions present in endolymph. Mutations at the Ca2+-binding sites of tip-links often lead to congenital deafness, sometimes syndromic defects impairing vision along with hearing. Although such mutations are already identified, it is still not clear how the mutants alter the structure-function properties of the force-sensors associated with diseases. With an aim to decipher the differences in force-conveying properties of the force-sensors in molecular details, we identified the conformational variability of mutant and wild-type tip-links at the single-molecule level using FRET at the endolymphatic Ca2+ concentrations and subsequently measured the force-responsive behavior using single-molecule force spectroscopy with an AFM. AFM allowed us to mimic the high and wide range of force ramps (103 - 106 pN.s-1) as experienced in the inner ear. We performed in silico network analyses to learn that alterations in the conformations of the mutants interrupt the natural force-propagation paths through the sensors and make the mutant tip-links vulnerable to input forces from sound stimuli. We also demonstrated that a Ca2+ rich environment can restore the force-response of the mutant tip-links which may eventually facilitate the designing of better therapeutic strategies to the hearing loss.\n\nSignificance StatementForce-sensors in inner ear are the key components in the hearing. Mutations in force-sensors often lead to congenital hearing loss. Loss of hearing has become a threat to humanity, with over 5% of world population suffering from deafness and 40% of which is congenital, primarily due to mutations in the sensory machinery in inner-ear. A better understanding of the molecular mechanism of the underlined hearing loss due to mutations is, therefore, necessary for better therapeutics to deaf. Here with a zoomed region of the force-sensors, we pointed out the differences in the force-propagation properties of the mutant and wild-type force-sensors. Our observation on restoring of functions of mutants in Ca2+-rich buffer indicates methods of developing low-cost therapeutic strategies against deafness.

biophysics↗

bioRxiv2019

A spatial cell culture model for predicting chemotherapy dosing strategies

Predicting patient responses to chemotherapy regimens is a major challenge in cancer treatment. To do this requires quantitative mathematical models to predict optimal dose and frequency for a particular drug, and experimental model systems such as three-dimensional organoids that accurately recapitulate the tumor microenvironment and heterogeneity. However, tracking the spatial dynamics of multiple cell types in three-dimensions can be a significant challenge in terms of time and throughput. Here we develop a two-dimensional system that allows for simple tracking of cell populations via fluorescence microscopy for modeling spatial dynamics in tumors. We first develop multiple 4T1 breast cancer cell lines resistant to varying concentrations of doxorubicin, and demonstrate how well mixed and spatially heterogeneous populations expand in a two-dimensional colony. We subject cell populations to varied dose and frequency of chemotherapy and measure colony growth radius and populations. We then build a mathematical model to describe the dynamics of both chemosensitive and chemoresistant populations, where we determine which number of doses can produce the smallest tumor size based on parameters in the system. In the future, this system can be adapted to quickly optimize dosing strategies in the setting of heterogeneous cell types or patient derived cells with varied chemoresistance.

cancer biology↗

bioRxiv2019

An oomycete RXLR effector triggers antagonistic plant hormone crosstalk to suppress host immunity

Understanding the mechanisms through which pathogens alter plant cell networks is essential for understanding plant-pathogen interactions and will inform efforts to reduce crop diseases. Oomycetes secrete diverse effector proteins into plant cells. The mechanisms through which these effectors promote virulence are largely unknown. We show that the HaRxL10 effector protein from the Arabidopsis thaliana pathogen Hyaloperonospora arabidopsidis (Hpa) targets a transcriptional repressor (JAZ3) involved in jasmonic acid (JA) signalling. This manipulation activates a regulatory cascade that inhibits salicylic acid (SA) signalling, which normally restricts Hpa infection. This virulence mechanism is functionally equivalent to but mechanistically distinct from activation of the antagonistic JA-SA hormone crosstalk by the bacterial JA-mimicking toxin coronatine and by bacterial Type III effectors. These results reveal a key role for JAZ3 in plant immunity and emphasize that JA-SA crosstalk is an Achilles heel in the plant immune system, vulnerable to manipulation by diverse microbes.

plant biology↗