Biology subjects

Ravi, K.

Publications and source records attributed to Ravi, K..

6 recordsLinked to original sources

bioRxiv2026

A robust, reproducible, accessible and scalable protocol for generating three-dimensional human gastruloids

The rapid rise of stem cell-based human embryo models has reignited interest in studying early human development while offering a promising platform to de-risk drugs. Among these, three-dimensional human gastruloids provide a tractable system to model symmetry breaking, germ layer specification and axial organization. However, existing gastruloid protocols remain expensive, specialized, variable and evaluated in a limited number of human pluripotent stem cell (hPSC) lines, restricting broader adoption. Here, we present a simple, robust, standardized gastruloid protocol achieving greater than 90% elongation efficiency with low inter- and intra-experimental variability, developed primarily in BJNhem20, a well-characterized Indian-origin human embryonic stem cell line. Further, we show that the protocol is applicable in a diverse set of hPSC lines. Using a TBXT (Brachyury)-GFP reporter in BJNhem20, we optimized cell seeding density, induction medium and Wnt activation strength, guided by real-time, quantitative assessment of mesoderm induction and symmetry breaking, allowing precise titration of CHIR99021. Comparative testing identified an in-house "Essential 6" medium formulation as the most consistent condition for robust TBXT induction. Optimization of aggregation density produced reproducible gastruloids with polarized TBXT expression and consistent axial elongation, within 72 hours. Single-cell RNA sequencing of individual gastruloids confirmed high transcriptional reproducibility and conserved lineage clusters, aligned with developmental trajectories. Cell line-specific CHIR99021 titration was sufficient to successfully transfer the optimized protocol to two additional lines, BJNhem19 and RUES2-GLR. This simplified and robust protocol reduces costs and improves accessibility, enabling broader application of stem cell-based human embryo models.

developmental biology↗

bioRxiv2026

Characterization of household microbiomes from three unique cities around the world

Characterizing the household bacterial microbiome allows for a stronger understanding of the various microbes that a person is exposed to everyday in their home. Exploring household microbiomes in different countries around the world increases - our understanding of the impact cultural differences might have on niche microbial communities in the house. The goal of this study was to use shotgun metagenomics to characterize the microbiome for ten locations around the home in ten different houses from three different countries (Mysuru, India; Dubai, United Arab Emirates (UAE); and Tucson, United States of America (USA)). There was a significant difference in alpha diversity between the three countries (ANOVA, p<0.05) with homes in Mysuru, India showing significantly higher bacterial diversity compared to Dubai, UAE and Tucson, AZ, USA. Beta diversity analysis of the homes found that bacterial communities significantly differed between cities (PERMANOVA, p<0.01) and within cities by household locations (PERMANOVA, p<0.001). Locations such as underneath the toilet rim, bathroom and kitchen sinks had the highest levels of bacterial diversity across the three cities compared to other sampling areas. A core microbiome of Actinomycetes and Gammaproteobacteria was found in all homes in all three cities. Within each city, a core microbiome was identified at the species level within specific household locations in each city. Over 90% of bacterial taxa found in the homes were a part of the human-associated phyla Actinomycetes (eg. genera Brevibacterium, Corynebacterium, and Microbacterium), Pseudomonadota (eg. genera Acinetobacter, Moraxella, Pantoea, Paracoccus, and Psuedomonas), and Bacillota (genus Streptococcus), which was comparable to previous studies. The household microbiome is variable in different locations in the house and on a global scale. Factors such as human activity, cultural practices, climate, and surface type and use may drive this diversity. Characterizing the household microbiome on a global scale allows for a better understanding of what drives microbial diversity, increasing our understanding of how microbial communities are shaped by the environment and how humans influence their dynamics, as well as any risks to human health that the built microbiome may potentially pose. Impact StatementThis research contributes to the understanding of the built microbiome, specifically how it varies within the house, within cities, and across the globe. This can aid in our understanding of microbial dynamics in environments with heavy human influence and help develop and improve hygiene habits and products which are mindful of the existing microbiome. Data SummaryDNA sequence data from this research is publicly available on the NCBIs Sequence Read Archive under BioProject PRJNA1416920. Data was analyzed using python and R code. Analysis protocols and information on software versions, packages, and more can be found within the text and in the following github repository: https://github.com/carolinescranton01/Global_Household_Microbiome. The authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files.

microbiology↗

bioRxiv2026

Assessment of the household antibiotic resistance gene, virulence factor genes, and pathogen profiles from three global cities

This study assessed the prevalence of antibiotic resistance genes (ARGs) and virulence factor genes (VFs), DNA viruses, and medically-relevant pathogens in three major cities around the globe - Mysuru (India), Dubai (United Arab Emirates), and Tucson (Arizona, United States of America). Ten households were sampled in each city, at ten sites in the bathroom, kitchen, and living spaces. The alpha diversity of ARGs significantly differed between household locations in each country (ANOVA, p<0.05) and beta diversity (dissimilarity) analysis showed a significant association between the ARGs and the geographic locations (PERMANOVA, p<0.01). A set of ARGs were found in every location across the dataset (the core ARG profile) included 25 different genes. The alpha diversity of virulence factors differed across the household locations within the three cities (ANOVA, p<0.01). The beta diversity of VFs was not well explained by geographic location or location within the household (PERMANOVA, p=0.129 (geographic), p=0.127 (household)). There were 341 unique VFs found in the study, but only 5 core VFs across the dataset. Bacterial pathogens detected across the household included Escherichia coli, Acinetobacter baumanii, Klebsiella pneumoniae, and more. The DNA (and bacteriophage) virome varied between countries and was more diverse in Tucson and Dubai (top viral families included Poxviridae and Orthoherpesviridae - two families which contain human pathogens - and Steitzviridae, a family of bacteriophages) compared to Mysuru, where nearly all viruses were a part of the Muvirus genus (a bacteriophage which contributes to horizontal gene transfer by phage transduction). ImportanceThe diversity of the built environment microbiome is not well characterized globally. Household occupants interact with the built microbiome on a daily basis, and the built microbiome may have the potential to influence human health. The presence of pathogens in the built environment and the key genes contributing to microorganism pathogenicity were investigated in this study, as information on this is lacking on an international scale. The diversity of ARG and VFs across the globe, as well as the presence of medically relevant pathogens within the house that were found in this study highlights the need to explore further the factors which influence the household microbiome, virome, and resistome. This may aid in identify how the build microbiome may be shaped by humans and influence human health. Impact StatementThis research contributes to the understanding of the built microbiome, specifically how it varies within the house, within cities, and across the globe. This can aid in our understanding of microbial dynamics in environments with heavy human influence and help develop and improve hygiene habits and products which are mindful of the existing microbiome.

microbiology↗

bioRxiv2024

Lung Microbiome Intervention Attenuates Herpesvirus-Induced Post-HCT Pulmonary Fibrosis Through PD-L1 Upregulation on Dendritic Cells

Alterations in the lung microbiome frequently accompany adverse pulmonary outcomes. Hematopoietic cell transplantation (HCT) markedly affects the lung microbiome corresponding with a high incidence of post-HCT pulmonary complications. In a preclinical mouse model of HCT, we observed a reduction in Lactobacillus johnsonii within the lung microbiome following transplantation. Intranasal administration of live or heat-killed (HK) L. johnsonii at low doses reduced gammaherpesvirus-induced pulmonary fibrosis in HCT mice, in which IL-17A plays an essential role. HK L. johnsonii treatment of HCT mice suppressed inflammatory cytokine production by lung macrophages and decreased Il17a expression in T helper 17 (Th17) cells. HK L. johnsonii increased PD-L1 expression on the surface of type II conventional dendritic cells (cDC2) in HCT mice and in vitro in bone marrow-derived dendritic cells (BMDCs). HK L. johnsonii-exposed BMDCs also inhibited IL-17A secretion from co-cultured Th17 cells in a PD-1-dependent manner. Notably, when HK L. johnsonii was administered to HCT mice reconstituted with bone marrow cells from PD-1 knockout (KO) mice, which lack a PD-L1 mediated response, HK L. johnsonii-mediated reduction of pulmonary fibrosis was negated. Collectively, our findings demonstrate that HK L. johnsonii mitigates herpesvirus-induced pulmonary fibrosis in HCT mice by modulating cDC2 surface expression of PD-L1, which subsequently suppresses Il17a expression in Th17 cells, pointing towards a potential postbiotic-based strategy for immunomodulation to address pulmonary complications of HCT.

immunology↗

bioRxiv2022

Multiple ParA/MinD ATPases coordinate the positioning of disparate cargos in a bacterial cell

In eukaryotes, linear motor proteins govern intracellular transport and organization. In bacteria, where linear motors are absent, the ParA/MinD (A/D) family of ATPases spatially organize an array of genetic- and protein-based cellular cargos. ParA is well known to segregate plasmids and chromosomes, as is MinD for its role in divisome positioning. Less studied is the growing list of ParA/MinD-like ATPases found across prokaryotes and involved in the spatial organization of diverse protein-based organelles, such as Bacterial Microcompartments (BMCs), flagella, chemotaxis clusters, and conjugation machinery. Given the fundamental nature of these processes in both cell survival and pathogenesis, the positioning of these cargos has been independently investigated to varying degrees in several organisms. However, it remains unknown whether multiple A/D ATPases can coexist and coordinate the positioning of such a diverse set of fundamental cargos in the same cell. If so, what are the mechanistic commonalities, variation, and specificity determinants that govern the positioning reaction for each cargo? Here, we find that over a third of sequenced bacteria encode multiple A/D ATPases. Among these bacteria, we identified several human pathogens as well as the experimentally tractable organism, Halothiobacillus neapolitanus, which encodes seven A/D ATPases. We directly demonstrate that five of these A/D ATPases are each dedicated to the spatial regulation of a single cellular cargo: the chromosome, the divisome, the carboxysome BMC, the flagellum, and the chemotaxis cluster. We identify putative specificity determinants that allow each A/D ATPase to position its respective cargo. Finally, we show how the deletion of one A/D ATPase can have indirect effects on the inheritance of a cargo actively positioned by another A/D ATPase, stressing the importance of understanding how organelle trafficking, chromosome segregation, and cell division are coordinated in bacterial cells. Together, our data show how multiple A/D ATPases coexist and function to position a diverse set of fundamental cargos in the same bacterial cell. With this knowledge, we anticipate the design of minimal autonomous positioning systems for natural- and synthetic-cargos in bacteria for synthetic biology and biomedical applications.

microbiology↗

bioRxiv2019

Single Cell Viewer (SCV): An interactive visualization data portal for single cell RNA sequence data

MotivationThanks to technological advances made in the last few years, we are now able to study transcriptomes from thousands of single cells. These have been applied widely to study various aspects of Biology. Nevertheless, comprehending and inferring meaningful biological insights from these large datasets is still a challenge. Although tools are being developed to deal with the data complexity and data volume, we do not have yet an effective visualizations and comparative analysis tools to realize the full value of these datasets.\n\nResultsIn order to address this gap, we implemented a single cell data visualization portal called Single Cell Viewer (SCV). SCV is an R shiny application that offers users rich visualization and exploratory data analysis options for single cell datasets.\n\nAvailabilitySource code for the application is available online at GitHub (http://www.github.com/neuhausi/single-cell-viewer) and there is a hosted exploration application using the same example dataset as this publication at http://periscopeapps.org/scv_tirosh.\n\nContactisaac.neuhaus@bms.com; kandasamy.ravi@bms.com

bioinformatics↗