Biology subjects

Bhatnagar, J.

Publications and source records attributed to Bhatnagar, J..

5 recordsLinked to original sources

bioRxiv2026

Soil nitrogen cycling rates are linked to microbial functional and taxonomic groups across the United States

Soil microbes support life on Earth by regulating the availability of nutrients in soils, yet we lack a fundamental, baseline knowledge of which fungi and bacteria are associated with specific soil nitrogen (N) cycling processes across ecosystems. We identified functional and taxonomic groups of fungi and bacteria that are associated with net ammonification and nitrification rates in soils from diverse ecosystems across the United States, including the environmental contexts where these relationships exist. To accomplish this, we co-analyzed soil, microbial, plant, and climatic data from 19 sites across the U.S. National Ecological Observatory Network (NEON). Distinct microbial groups were associated with net ammonification versus nitrification rates, highlighting the need to measure and model these two processes separately. The relative abundance of several microbial groups known for their N-decomposition abilities (i.e., Acidobacteriae, Bacteroidia, Saccharomycetes yeasts, ectomycorrhizal fungi) were positively associated with net ammonification rates across diverse environmental conditions. Meanwhile, pathogenic fungi, copiotrophic bacteria, and bacterial classes containing denitrifying bacteria were positively associated with net nitrification rates in many wet, hot, and high-N environments. These results deepen our understanding of soil microbiome ecology and represent a practical starting point to develop microbial-explicit biogeochemical cycling models at large spatial scales.

ecology↗

bioRxiv2025

SORLA upregulation suppresses global pathological effects in aged tauopathy mouse brain

A role for the trafficking receptor SORLA in reducing A{beta} levels has been well-established, however, relatively little is known with respect to whether and how SORLA can potentially affect tau pathology in vivo. Here, we show that transgenic SORLA upregulation (SORLA TG) can reverse pathological effects in aged PS19 (P301S tau) mouse brain, including tau phosphorylation and seeding, ventricle dilation, synapse loss, LTP impairment and glial hyperactivation. Proteomic analysis indicates reversion of PS19 profiles in PS19/SORLA TG hippocampus, including pathological changes in synapse-related proteins as well as key drivers of synaptic dysfunction such as Apoe and C1q. snRNA-seq analysis reveals suppression of PS19- signatures with SORLA upregulation, including proinflammatory induction of Plxnb1/Plxnb2 in glia. Tau seeding and aggregation, neuroinflammation, as well as PlxnB1/B2 induction are exacerbated in PS19 hippocampus with SORLA deletion. These results implicate a global role for SORLA in neuroprotection from tau toxicity in PS19 mouse brain.

neuroscience↗

bioRxiv2023

Urbanization and fragmentation interact to drive mutualism breakdown and the rise of unstable pathogenic communities in forest soil

Temperate forests are particularly threatened by urbanization and fragmentation, with over 20% (120lJ000 km2) of recently urbanized land in the U.S. subsuming natural forests. We leveraged a unique, well-characterized urban-to-rural and forest edge-to-interior gradient to identify the combined impact of these two land use changes - urbanization and forest fragmentation - on soil microbial community in native, remnant forests. We found evidence of mutualism breakdown between trees and their fungal root mutualists (ectomycorrhizal (ECM) fungi) with urbanization, where ECM fungi colonized fewer tree roots and had less connectivity in soil microbiome networks in urban forests compared to rural forests. However, urbanization did not reduce the relative abundance of ECM fungi in forest soils; instead, forest fragmentation alone led to strong reductions in ECM fungal abundance. At forest edges, ECM fungi were replaced by plant and animal pathogens, as well as copiotrophic, xenobiotics-degrading, and nitrogen-cycling bacteria, including nitrifiers and denitrifiers. Urbanization and fragmentation interacted to generate "suites" of microbes, with urban interior forests harboring highly homogenized microbiomes, while edge forests microbiomes were more heterogeneous and less stable, showing increased vulnerability to low soil moisture. When scaled to the regional level, we found that forest soils are projected to harbor high abundances of fungal pathogens and denitrifying bacteria, even in rural areas, due to extreme, widespread forest fragmentation. Our results highlight the potential for soil microbiome dysfunction - including increased greenhouse gas production - in temperate forest regions that are subsumed by urban expansion, both now and in the future. Significance StatementUrbanization and forest fragmentation are increasingly altering Earths ecosystems, yet the effects on soil microbiomes, crucial for plant health and climate regulation, remain unclear. Our data indicate that, in forested land, these two combined, compounding stressors reshape the soil microbiome in ways that could lead to more pathogen infections of plants and animals, higher rates of N loss due to denitrification, and the possibility of tree symbiont extinctions. By identifying the specific environmental stressors that lead to these microbiome shifts, our analysis can be used to inform urban development and forest management plans to mitigate impacts on the soil microbiome to sustain environmental quality and the ecosystem services that remnant native forests provide to society in the coming decades. ClassificationBiological Sciences/Ecology

ecology↗

bioRxiv2021

Optimality of extracellular enzyme production and activity in dynamic flux balance modeling

In microbial communities, many vital metabolic functions, including the degradation of cellulose, proteins and other complex macromolecules, are carried out by costly, extracellularly secreted enzymes. While significant effort has been dedicated to analyzing genome-scale metabolic networks for individual microbes and communities, little is known about the interplay between global allocation of metabolic resources in the cell and extracellular enzyme secretion and activity. Here we introduce a method for modeling the secretion and catalytic functions of extracellular enzymes using dynamic flux balance analysis. This new addition, implemented within COMETS (Computation Of Microbial Ecosystems in Time and Space), simulates the costly production and secretion of enzymes and their diffusion and activity throughout the environment, independent of the producing organism. After tuning our model based on data for a Saccharomyces cerevisiae strain engineered to produce exogenous cellulases, we explored the dynamics of the system at different cellulose concentrations and enzyme production rates. We found that there are distinct rates of constitutive enzyme secretion which maximize either growth rate or biomass yield. These optimal rates are strongly dependent on enzyme kinetic properties and environmental conditions, including the amount of cellulose substrate available. Our framework will facilitate the development of more realistic simulations of microbial community dynamics within environments rich in complex macromolecules, with applications in the study of soil and plant-associated ecosystems, and other natural and engineered microbiomes. ImportanceMany organisms - including soil, marine and human-associated bacteria and fungi - perform part of their metabolic functions outside of the boundary of the cell, through the secretion of extracellular enzymes that can diffuse and facilitate reactions independently of the organism that produced them. In order to better understand and predict microbial ecosystems, it would be helpful to create mathematical models incorporating these extracellular reactions within simulations of metabolism at the whole-cell level. In this paper we demonstrate the implementation of such a methodology and apply it to study a cellulase-secreting yeast. This work will be useful for a number of microbial ecology applications, including modeling of microbiome dynamics, engineering of bioproducts (e.g. biofuels) from plant biomass through synthetic communities or modified organisms, and testing of basic ecological hypotheses about the balance between cost and benefits of the production of common goods in microbial communities.

systems biology↗

bioRxiv2018

Global climate changes will lead to regionally divergent trajectories for ectomycorrhizal communities in North American Pinaceae forests

Ectomycorrhizal fungi (ECMF) are partners in a globally distributed tree symbiosis that enhanced ecosystem carbon (C)-sequestration and storage. However, resilience of ECMF to future climates is uncertain. We sampled ECMF across a broad climatic gradient in North America, modeled climatic drivers of diversity and community composition, and then forecast ECMF response to climate changes over the next 50 years. We predict ECMF richness will decline over nearly half of North American Pinaceae forests, with median species losses as high as 21%. Mitigation of greenhouse gas emissions can reduce these declines, but not prevent them. Warming of forests along the boreal-temperate ecotone results in projected ECMF species loss and declines in the relative abundance of C demanding, long-distance foraging ECMF species, but warming of eastern temperate forests has the opposite effect. Sites with more ECMF species had higher activities of nitrogen-mineralizing enzymes, suggesting that ECMF species-losses will compromise their associated ecosystem functions.

ecology↗