Biology subjects

Contreras, J.

Publications and source records attributed to Contreras, J..

6 recordsLinked to original sources

bioRxiv2026

Dairy wastewater grease stabilizes in situ mesophilic biomethanation for H2-to-CH4 conversion

Power-to-Gas technologies are emerging as a key strategy to integrate surplus renewable electricity into energy systems, through the conversion of green hydrogen into methane. However, the practical implementation of biological in situ biomethanation is still constrained by operational and design requirements that are incompatible with most existing anaerobic digestion infrastructures. This study demonstrates a stable and efficient mesophilic (37{degrees}C) in situ biomethanation process driven by substrate-induced microbial selection rather than relying on continuous hydrogen supply. Anaerobic digesters co-digesting sewage sludge from a wastewater treatment plant with lipid-rich greases recovered from dairy wastewater developed a pre-adapted hydrogenotrophic consortium capable of effective CO2-H2 conversion under mesophilic conditions. Long-term operation confirmed the robustness and persistence of this microbial structure. Upon H2 addition, methane concentrations up to 82 % were achieved under atmospheric pressure, without biogas recirculation, with hydrogen-to-methane conversion efficiencies up to 90% and methane productivities of 1.64 NLCH4.L-1d-1. 16SrRNA-based microbial community analysis revealed that dairy grease co-digestion selectively enriched hydrogenotrophic methanogens, particularly Methanospirillum, together with syntrophic fatty-acid-degrading bacteria such as Syntrophomonas, promoting efficient interspecies hydrogen transfer. Importantly, the lipid co-substrate enabled the establishment and long-term stability of the hydrogenotrophic pathway independently of hydrogen availability, mitigating challenges associated with intermittent renewable energy supply. Overall, these findings challenge the common reliance on thermophilic conditions, continuous hydrogen input, pressurization, and gas recirculation in in situ biomethanation, demonstrating that substrate-driven microbial selection can replace conventional engineering requirements such as thermophilic operation or reactor modifications, providing a simpler and scalable strategy for mesophilic in situ biomethanation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/731101v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@c62086org.highwire.dtl.DTLVardef@1813ed6org.highwire.dtl.DTLVardef@4462bcorg.highwire.dtl.DTLVardef@1ae2cfb_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG Highlights- Lipid-assisted co-digestion promotes stable biogas and biomethane production - Dairy wastewater greases enable mesophilic in situ biomethanation - An enriched hydrogenotrophic methanogenic consortium yields >82% CH4 - 70-90% H2-to-CH4 conversion efficiency under mesophilic, unpressurized conditions - Substrate-driven microbial selection enables in situ biomethanation in WWTP digesters

bioengineering↗

bioRxiv2025

Nutrient requirements for cell differentiation progression in Batrachochytrium dendrobatidis

Batrachochytrium dendrobatidis (Bd) is the causative agent of the deadly amphibian disease chytridiomycosis, which has decimated amphibian populations across the globe. Bd reproduces via a multistage asexual pathway. The Bd life cycle begins with a motile zoospore. Upon contact with a surface, the zoospore anchors itself and forms a cyst. The cyst then develops into a germling that produces rhizoid structures. Finally, the germling matures into a zoosporangium which then releases multiple new zoospores. In this study, we investigated the effects of nutrients on the growth and differentiation of Bd. The presence of carbohydrates, vitamins, and trace minerals had a negligible effect on Bds ability to progress through its life cycle. In contrast, the amino acids L-leucine and L-isoleucine (and to a lesser extent L-arginine) were required for cysts to germinate into germlings. However, none of these amino acids were able to sustain further cellular development. Furthermore, the presence of nitrate or ammonium aided progression from germlings into immature zoosporangia that were not able to produce zoospores. The progression to mature zoosporangia was blocked by nitrite or the combined action of calcium ions and bicarbonate. The addition of soluble and insoluble protein sources alone also allowed Bd to develop into immature zoosporangia and affected the rate of development. Finally, protein sources in combination with L-amino acids allowed the completion of the Bd cycle by allowing development from zoospores to mature zoosporangia that were able to release new zoospores. ImportanceEven though the cell differentiation cycle of Bd has been microscopically described, not much is known about the requirements for Bd to progress throughout its life stages. The identification of the molecular cues that allow Bd cell cycle progression may be crucial to disease mitigation efforts. As a corollary, we have identified conditions that allow for the arrest of Bd at various stages of its life cycle. By changing the metabolite availability, we can efficiently obtain cultures enriched for zoospores, cysts, germlings, immature zoosporangia, or spore-releasing zoosporangia. The ability to temporarily freeze and then restart Bd at different points of its life cycle, can allow for determining the mechanisms behind individual transitions between cell types.

microbiology↗

bioRxiv2025

Perivascular space mediated the interaction between sleep, and brain functional connectivity in the healthy aging population

Perivascular space (PVS) surrounds the perforating arteries or draining veins of the cerebral cortex as part of the brain clearance system. Previous studies showed that sleep aTects both brain clearance function and brain functional connectivity (FC). However, the impact of PVS characteristics on brain FC remains unclear. This study investigated these associations and their link to cognition. We utilized cross-sectional structural MRI and resting state-fMRI data from 512 health aging population in the HCP-Aging dataset, together with Pittsburgh Sleep Quality Index questionnaire and NIH cognitive tests. Our results showed that basal ganglia (BG)-PVS volume fraction (VF) was positively correlated with FC in the right anterior medial temporal gyrus (aMTG) and right temporal regions, while centrum-semiovale (CSO)-PVS VF was positively correlated with FC in the left hippocampus and right frontal regions. Increased CSO-PVS VF in early middle-aged adults showed higher hippocampal FC and better cognitive performance. Interestingly, individuals with longer time spent in bed had larger BG-PVS VF linked to higher FC in the right aMTG. Additionally, older adults with better sleep quality had larger BG-PVS VF linked to higher FC in the right aMTG. These findings suggest that PVS morphology may reflect changes in neural connections involved in memory-related regions.

neuroscience↗

bioRxiv2023

Tiered Sympathetic Control of Cardiac Function Revealed by Viral Tracing and Single Cell Transcriptome Profiling

The cell bodies of postganglionic sympathetic neurons innervating the heart primarily reside in the stellate ganglion (SG), alongside neurons innervating other organs and tissues. Whether cardiac-innervating stellate ganglionic neurons (SGNs) exhibit diversity and distinction from those innervating other tissues is not known. To identify and resolve the transcriptomic profiles of SGNs innervating the heart we leveraged retrograde tracing techniques using adeno-associated virus (AAV) expressing fluorescent proteins (GFP or Td-tomato) with single cell RNA sequencing. We investigated electrophysiologic, morphologic, and physiologic roles for subsets of cardiac-specific neurons and found that three of five adrenergic SGN subtypes innervate the heart. These three subtypes stratify into two subpopulations; high (NA1a) and low (NA1b and NA1c) Npy-expressing cells, exhibit distinct morphological, neurochemical, and electrophysiologic characteristics. In physiologic studies in transgenic mouse models modulating NPY signaling, we identified differential control of cardiac responses by these two subpopulations to high and low stress states. These findings provide novel insights into the unique properties of neurons responsible for cardiac sympathetic regulation, with implications for novel strategies to target specific neuronal subtypes for sympathetic blockade in cardiac disease.

neuroscience↗

bioRxiv2022

Unbiased stereologic estimates of dopaminergic and GABAergic neurons in the A10, A9, and A8 subpopulations in the young male Macaque

The ventral midbrain is the primary source of dopamine- (DA) expressing neurons in most species. GABA-ergic and glutamatergic cell populations are intermixed among DA-expressing cells and purported to regulate both local and long-range dopamine neuron activity. Most work has been conducted in rodent models, however due to evolutionary expansion of the ventral midbrain in primates, the increased size and complexity of DA subpopulations warrants further investigation. Here, we quantified the number of DA neurons, and their GABA-ergic complement in classic DA cell groups A10 (midline ventral tegmental area nuclei [VTA] and parabrachial pigmented nucleus [PBP]), A9 (substantia nigra, pars compacta [SNc]) and A8 (retrorubral field [RRF]) in the macaque. Because the PBP is a disproportionately expanded feature of the A10 group, and has unique connectional features in monkeys, we analyzed A10 data by dividing it into classic midline nuclei and the PBP. Unbiased stereology revealed total putative DA neuron counts to be 210,238 +/- 17,127 (A10 = 110,319 +/- 9,649, A9= 87,399 +/-7,751 and A8=12,520 +/- 827). Putative GABAergic neurons were fewer overall, and evenly dispersed across the DA subpopulations (GAD67= 71,215 +/- 5,663; A10=16,836 +/- 2,743; A9=24,855 +/- 3,144 and A8=12,633 +/- 3,557). Calculating the GAD67/TH ratio for each subregion revealed differential balances of these two cell types across the DA subregions. The A8 subregion had the highest complement of GAD67-positive neurons compared to TH-positive neurons (1:1), suggesting a potentially high capacity for GABAergic inhibition of DA output in this region. HIGHLIGHTSO_LIThe A10 subregion expands laterally and caudally in nonhuman primates C_LIO_LIThe A10, A9, and A8 comprise 52%, 42% and 6% of DA neurons, respectively C_LIO_LIGABAergic neurons are more evenly dispersed across subregions C_LIO_LIThe A8 subpopulation has the highest ratio of GABA: DA neurons C_LI

neuroscience↗

bioRxiv2021

Neutrophils contribute to ER stress in lung epithelial cells in the pristane-induced diffuse alveolar hemorrhage mouse model

Diffuse alveolar hemorrhage (DAH), although rare, is a life-threatening complication of systemic lupus erythematosus (SLE). Little is known about the pathophysiology of DAH in humans, although increasingly neutrophils, NETosis and inflammatory monocytes have been shown to play an important role in the pristane-induced model of SLE which develops lung hemorrhage and recapitulates many of the pathologic features of human DAH. Using this experimental model, we asked whether endoplasmic reticulum (ER) stress played a role in driving the pathology of pulmonary hemorrhage and what role infiltrating neutrophils had in this process. Analysis of lung tissue from pristane-treated mice showed genes associated with ER stress and NETosis were increased in a time-dependent manner and reflected the timing of CD11b+Ly6G+ neutrophil accumulation in the lung. Using precision cut lung slices from untreated mice we observed that neutrophils isolated from the peritoneal cavity of pristane-treated mice could directly induce the expression of genes associated with ER stress, namely Chop and Bip. Mice which had myeloid-specific deletion of PAD4 were generated and treated with pristane to assess the involvement of PAD4 and PAD4-dependent NET formation in pristane-induced lung inflammation. Specific deletion of PAD4 in myeloid cells resulted in decreased expression of ER stress genes in the pristane model, with accompanying reduction in IFN-driven genes and pathology. Lastly, coculture experiments of human neutrophils and human lung epithelial cell line (BEAS-2b) showed neutrophils from SLE patients induced significantly more ER stress and interferon-stimulated genes in epithelial cells compared to healthy control neutrophils. These results support a pathogenic role of neutrophils and NETs in lung injury during pristane-induced DAH through the induction of ER stress response and suggest that overactivation of neutrophils in SLE and NETosis may underlie development of DAH.

immunology↗