Biology subjects

Tripathi, A.

Publications and source records attributed to Tripathi, A..

At least 37 records · Page 2Linked to original sources

bioRxiv2025

Somatostatine interneurons mediate dopamine-dependent sensory gating in the orbitofrontal cortex

The prefrontal cortex continuously filters irrelevant stimuli, and deficits in this sensory gating predispose to psychotic disorders. In schizophrenia, the normally observed suppression of second response to two paired sounds is drastically reduced. Apart from sensitivity to critical schizophrenia players as NMDA and dopamine, the microcircuitry behind gating remains unknown. We found that the first sound excitatory response recruits, via NMDA receptors, local inhibition to gate the second response via GABAB receptors. Optogenetic inhibition of somatostatine-interneurons counteracted gating more effectively compared to parvalbumine-positive interneurons. Dopamine local blockade also counteracted gating, and dopamine effect was prevented by somatostatine-, but not parvalbumine-, optoactivation. Thus, prefrontal gating is mediated by NMDA-dependent recruitment of dendrite-targeting, somatostatine-interneurons, facilitated by dopamine. The results identify a critical synapse to better target psychose-prone disorders.

neuroscience↗

bioRxiv2025

Degradation of ribosomal RNA during Plasmodium falciparum gametocytogenesis

The life cycle of Plasmodium falciparum is characterized by complex regulatory changes that allow adaptation of the parasites to different environmental conditions, which are especially pronounced during transmission between the mammalian host and the insect vector. Previous studies have shown that P. falciparum uses three types of ribosomal RNAs (rRNA A-, S1- and S2-types) at different stages of its life cycle. We used Oxford Nanopore Technologies (ONT) direct RNA sequencing to investigate the dynamics of rRNA usage throughout the parasites intraerythrocytic development, as well as in salivary gland sporozoites. Our study revealed a preponderance of A-type rRNAs during the intraerythrocytic cycle and gametocytogenesis, while S-type rRNAs slowly increase in abundance in mosquito stages starting three days post infection. Salivary gland sporozoites showed an even proportion of all rRNA types. By examining the length distributions of rRNA molecules, we detected an extensive and specific degradation of rRNAs during gametocytogenesis, starting in stage II gametocytes and continuing until the final stages of gametocyte development. We hypothesize that rRNA degradation may be linked to the global translational repression and metabolic quiescence described in stage V gametocytes, similar to mechanisms observed in bacterial and eukaryotic stress responses.

microbiology↗

bioRxiv2024

Nanotextured steel surface exhibits antifungal activity

Fungal adhesion to stainless steel, an alloy commonly used in food and beverage sectors, public and healthcare settings, and numerous medical devices, can give rise to serious infections, ultimately leading to morbidity, mortality, and significant healthcare expenses. In this study, we demonstrate that nanotextured stainless steel (nSS) fabricated using an electrochemical technique is an antibiotic-free biocidal surface against Candida Albicans and Fusarium Oxysporum with 98% and 97% reduction, respectively. The nanoprotrusion features on nSS can have both physical contact with cell membranes and chemical impact on cells through production of reactive species, this material should not contribute to drug resistant fungus as antibiotics can. As nSS is also antibacterial and compatible with mammalian cells, demonstration of antifungal activity gives nSS the potential to be used to create effective, scalable, and sustainable solutions to broadly and responsibly prevent fungal and other microbial infections caused by surface contamination. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/616307v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@9c037dorg.highwire.dtl.DTLVardef@a93518org.highwire.dtl.DTLVardef@dccc6forg.highwire.dtl.DTLVardef@1f19515_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

Dietary L-3,4-dihydroxyphenylalanine (L-DOPA) augments cuticular melanization in Anopheles mosquitos while reducing their lifespan and malaria parasite burden

L-3,4-dihydroxyphenylalanine (L-DOPA), a naturally occurring tyrosine derivative, is prevalent in environments that include mosquito habitats, potentially serving as part of their diet. Given its role as a precursor for melanin synthesis we investigate the effect of dietary L-DOPA on mosquito physiology and immunity to Plasmodium falciparum and Cryptococcus neoformans infection. Dietary L-DOPA is incorporated into mosquito melanin via a non-canonical pathway and has a profound transcriptional effect associated with enhanced immunity, increased pigmentation, and reduced lifespan. Increased melanization results in an enhanced capacity to absorb electromagnetic radiation that affects mosquito temperatures. Bacteria in the mosquito microbiome act as sources of dopamine, a substrate for melanization. Our results illustrate how an environmentally abundant amino acid analogue can affect mosquito physiology and suggest its potential usefulness as an environmentally friendly vector control agent to reduce malaria transmission, warranting further research and field studies.

microbiology↗

bioRxiv2024

Dynamics of amylopectin granule accumulation during the course of the chronic Toxoplasma infection is linked to intra-cyst bradyzoite replication.

The contribution of amylopectin granules (AG), comprised of a branched chain storage homopolymer of glucose, to the maintenance and progression of the chronic Toxoplasma gondii infection has remained undefined. Here we describe the role of AG in the physiology of encysted bradyzoites by using a custom developed imaging-based application AmyloQuant that permitted quantification of relative levels of AG within in vivo derived tissue cysts during the initiation and maturation of the chronic infection. Our findings establish that AG are dynamic entities, exhibiting considerable heterogeneity among tissue cysts at all post infection time points examined. Quantification of relative AG levels within tissue cysts exposes a previously unrecognized temporal cycle defined by distinct phases of AG accumulation and utilization over the first 6 weeks of the chronic phase. This AG cycle is temporally coordinated with overall bradyzoite mitochondrial activity implicating amylopectin in the maintenance and progression of the chronic infection. In addition, the staging of AG accumulation and its rapid utilization within encysted bradyzoites was associated with a burst of coordinated replication. As such our findings suggest that AG levels within individual bradyzoites, and across bradyzoites within tissue cysts may represent a key component in the licensing of bradyzoite replication, intimately linking stored metabolic potential to the course of the chronic infection. This extends the impact of AG beyond the previously assigned role that focused exclusively on parasite transmission. These findings force a fundamental reassessment of the chronic Toxoplasma infection, highlighting the critical need to address the temporal progression of this crucial stage in the parasite life cycle.

microbiology↗

bioRxiv2024

Sarm1-Dependent Metabolic Reprogramming of Schwann Cells Following Nerve Injury

Schwann cells (SCs) transition into a Repair state after peripheral nerve injury; however, the early SC injury response preceding this transition remains poorly understood. We demonstrate that Sarm1, a key regulator of axon degeneration, is expressed and upregulated in SCs after nerve injury. Cell-type-specific Sarm1 knockout SCs exhibit enhanced axon protection in vitro, and SC- and glia-specific Sarm1 deletion confers axon protection in mouse sciatic nerve and Drosophila wing injury models. Single-nucleus RNA sequencing revealed that Sarm1-deficient SCs are enriched in a distinct cluster expressing genes with developmental roles in axon and myelin protection, with increased oxidative phosphorylation gene expression across all injured SC states. We propose that Sarm1 gates the transition from a Protection-Associated Schwann Cell (PASC) state to a Repair SC state, establishing Sarm1 as a multi-functional regulator with implications for peripheral neuropathies and neurodegenerative diseases.

neuroscience↗

bioRxiv2024

Nrf2 regulates the activation-driven expansion of CD4+ T-cells by differentially modulating glucose and glutamine metabolism

SUMMARYUpon antigenic stimulation, CD4+T-cells undergo clonal expansion, elevating their bioenergetic demands and utilization of nutrients like glucose and glutamine. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a well-known regulator of oxidative stress, but its involvement in modulating the metabolism of CD4+T-cells remains unexplored. Here, we elucidate the role of Nrf2 beyond the traditional antioxidation, in modulating activation-driven expansion of CD4+T-cells by influencing their nutrient metabolism. T-cell-specific activation of Nrf2 enhances early activation and IL-2 secretion, upregulates TCR-signaling, and increases activation-driven proliferation of CD4+T-cells. Mechanistically, high Nrf2 inhibits glucose metabolism through glycolysis but promotes glutamine metabolism via glutaminolysis to support increased T-cell proliferation. Further, Nrf2 expression is temporally regulated in activated CD4+T-cells with elevated expression during the early activation, but decreased expression thereafter. Overall, our findings uncover a novel role of Nrf2 as a metabolic modulator of CD4+T-cells, thus providing a framework for improving Nrf2-targeting therapies and T-cell immunotherapies.

immunology↗

bioRxiv2024

α7 nicotinic acetylcholine receptors are necessary for basal forebrain activation to increase expression of the nerve growth factor receptor TrkA

Activation of the basal forebrain leads to increases in the expression of the nerve growth factor receptor, Tropomyosin receptor kinase A (TrkA) and decreases in expression of the beta amyloid cleavage enzyme 1 (BACE1) in the cerebral cortex of both sexes of 5xFAD mice. The studies described in this report were designed to determine if these changes were dependent on acetylcholine receptors. Mice were stimulated unilaterally in the basal forebrain for two weeks. Animals were administered a cholinergic antagonist, or saline, 30 minutes prior to stimulation. Animals administered saline exhibited significant increases in TrkA expression and decreases in BACE1 in the stimulated hemisphere relative to the unstimulated. While both nonselective nicotinic and muscarinic acetylcholine receptor blockade attenuated the BACE1 decline, only the nicotinic receptor antagonism blocked the TrkA increase. Next, we applied selective nicotinic antagonists, and the 7 antagonist blocked the TrkA increases, but the 4{beta}2 antagonist did not. BACE1 declines were not blocked by either intervention. Mice with a loxP conditional knockout of the gene for the 7 nicotinic receptor were also employed in these studies. Animals were either stimulated bilaterally for two weeks, or left unstimulated. With or without stimulation, the expression of TrkA receptors was lower in the cortical region with the 7 nicotinic receptor knockdown. We thus conclude that 7 nicotinic receptor activation is necessary for normal expression of TrkA and increases caused by basal forebrain activation, while BACE1 declines caused by stimulation have dependency on a broader array of receptor subtypes.

neuroscience↗

bioRxiv2024

Endothelial fatty acid-binding proteins contribute to the pathogenesis of pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a devastating disease characterized by obliterative vascular remodeling and persistent increase of vascular resistance, leading to right heart failure and premature death. Understanding the cellular and molecular mechanisms will help develop novel therapeutic approaches for PAH patients. Single-cell RNA sequencing (scRNAseq) analysis found that both FABP4 and FABP5 were highly induced in endothelial cells (ECs) of Egln1Tie2Cre (CKO) mice, which was also observed in pulmonary arterial ECs (PAECs) from idiopathic PAH (IPAH) patients, and in whole lungs of pulmonary hypertension (PH) rats. Plasma levels of FABP4/5 were upregulated in IPAH patients and directly correlated with severity of hemodynamics and biochemical parameters using plasma proteome analysis. Genetic deletion of both Fabp4 and 5 in CKO mice (Egln1Tie2Cre/Fabp4-5-/-, TKO) caused a reduction of right ventricular systolic pressure (RVSP) and RV hypertrophy, attenuated pulmonary vascular remodeling and prevented the right heart failure assessed by echocardiography, hemodynamic and histological analysis. Employing bulk RNA-seq and scRNA-seq, and spatial transcriptomic analysis, we showed that Fabp4/5 deletion also inhibited EC glycolysis and distal arterial programming, reduced ROS and HIF-2 expression in PH lungs. Thus, PH causes aberrant expression of FABP4/5 in pulmonary ECs which leads to enhanced ECs glycolysis and distal arterial programming, contributing to the accumulation of arterial ECs and vascular remodeling and exacerbating the disease.

molecular biology↗

bioRxiv2023

A negative feedback loop is critical for recovery of RpoS after stress in Escherichia coli.

RpoS is an alternative sigma factor needed for the induction of the general stress response in many gammaproteobacteria. Tight regulation of RpoS levels and activity is required for bacterial growth and survival under stress. In Escherichia coli, various stresses lead to higher levels of RpoS due to increased translation and decreased degradation. During non-stress conditions, RpoS is unstable, because the adaptor protein RssB delivers RpoS to the ClpXP protease. RpoS degradation is prevented during stress by the sequestration of RssB by anti-adaptors, each of which is induced in response to specific stresses. Here, we examined how the stabilization of RpoS is reversed during recovery of the cell from stress. We found that RpoS degradation quickly resumes after recovery from phosphate starvation, carbon starvation, and when transitioning from stationary phase back to exponential phase. This process is in part mediated by the anti-adaptor IraP, known to promote RpoS stabilization during phosphate starvation via the sequestration of adaptor RssB. The rapid recovery from phosphate starvation is dependent upon a feedback loop in which RpoS transcription of rssB, encoding the adaptor protein, plays a critical role. Crl, an activator of RpoS that specifically binds to and stabilizes the complex between the RNA polymerase and RpoS, is also required for the feedback loop to function efficiently, highlighting a critical role for Crl in restoring RpoS basal levels. Author summaryIn their native environments, bacteria are exposed to constant changes in nutrient availability, as well as other biotic and abiotic stressors. To adjust to these changes, bacteria must rewire gene expression to adapt to or avoid stress-induced damage. A key player in the global response to general stresses is the alternative sigma factor RpoS, a promoter-specificity determining subunit of RNA polymerase. RpoS levels increase with stress, due to increased translation and stabilization of the otherwise unstable RpoS protein. Here, we examine how the cell restores homeostasis after the stress has passed. We show that a negative feedback loop in which RpoS regulates the transcription of an adaptor for proteolysis poises the cell to rapidly resume RpoS degradation upon the exit from stress.

microbiology↗

bioRxiv2023

Dicer deficiency in microglia leads to accelerated demyelination and failed remyelination

Microglia are the resident immune cells of the central nervous system (CNS) and are important regulators of normal brain functions. In CNS demyelinating diseases like multiple sclerosis (MS), the functions of these cells are of particular interest. Here we probed the impact of microRNA (miRNA)-mediated post-transcriptional gene regulation using a mouse model lacking microglia/macrophage-specific Dicer expression during demyelination and remyelination. Conditional Dicer ablation and loss of miRNAs in adult microglia led to extensive demyelination and impaired myelin processing. Interestingly, demyelination was accompanied by increased apoptosis of mature oligodendrocytes (OLs) and arresting OL progenitor cells (OPCs) in the precursor stage. At the transcriptional level, Dicer-deficient microglia led to downregulation of microglial homeostatic genes, increased cell proliferation, and a shift towards a disease-associated phenotype. Loss of remyelination efficiency in these mice was accompanied by stalling of OPCs in the precursor stage. Collectively, these results highlight a new role of microglial miRNAs in promoting a pro-regenerative phenotype in addition to promoting OPC maturation and differentiation during demyelination and remyelination. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/562812v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@71b542org.highwire.dtl.DTLVardef@13338b3org.highwire.dtl.DTLVardef@1cfa6c0org.highwire.dtl.DTLVardef@1ccc099_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2023

Dual antibacterial properties of copper coated nanotextured stainless steel

Bacterial adhesion to stainless steel, an alloy commonly used in shared settings, numerous medical devices, and food and beverage sectors, can give rise to serious infections, ultimately leading to morbidity, mortality, and significant healthcare expenses. In this study, we have demonstrated Cu-coated nanotextured stainless steel (nSS) fabrication using electrochemical technique and its potential as an antibiotic-free biocidal surface against Gram-positive and negative bacteria. As nanotexture and Cu combine for dual methods of killing, this material should not contribute to drug resistant bacteria as antibiotic use does. Our approach involves applying a Cu coating on nanotextured stainless steel, resulting in a antibacterial activity within 30 minutes. We have performed comprehensive characterization of the surface revealing that the Cu coating consists of metallic Cu and oxidized states (Cu2+ and Cu+). Cu-coated nSS induces a remarkable reduction of 97% in Gram-negative Escherichia coli and 99% Gram-positive Staphylococcus epidermidis bacteria. This material has potential to be used to create effective, scalable, and sustainable solutions to prevent bacterial infections caused by surface contamination without contributing to antibiotic resistance. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/563111v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@1d7e8f4org.highwire.dtl.DTLVardef@1feff9borg.highwire.dtl.DTLVardef@3f4224org.highwire.dtl.DTLVardef@10f8207_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Poly-basic peptides and polymers as new drug candidate against Plasmodium falciparum

Plasmodium falciparum, the malaria-causing parasite, is a leading cause of infection-induced deaths worldwide. The preferred treatment approach is artemisinin-combination therapy, which couples fast-acting artemisinin derivatives with longer-acting drugs like lumefantrine, mefloquine, and amodiaquine. However, the urgency for new treatments has risen due to the parasites growing resistance to existing therapies. Our study shows that a common characteristic of the P. falciparum proteome - stretches of poly-lysine residues such as those found in proteins related to adhesion and pathogenicity - can serve as an effective peptide treatment for infected erythrocytes. A single dose of these poly-basic peptides can successfully diminish parasitemia in human erythrocytes in vitro with minimal toxicity. The effectiveness of the treatment correlates with the length of the poly-lysine peptide, with 30 lysine peptides supporting the eradication of erythrocytic parasites within 72 hours. PEG-ylation of the poly-lysine peptides or utilizing poly-lysine dendrimers and polymers further increases parasite clearance efficiency and bolsters the stability of these potential new therapeutics. Lastly, our affinity pull-downs and mass-spectrometry identify P. falciparums outer membrane proteins as likely targets for polybasic peptide medications. Since poly-lysine dendrimers are already FDA-approved for drug delivery, their adaptation as antimalarial drugs presents a promising new therapeutic strategy. One-Sentence SummaryOur study demonstrates that poly-lysine peptides, particularly those modified through PEG-ylation or in the form of poly-lysine dendrimers, can effectively reduce Plasmodium falciparum, the causative agent of malaria, in human erythrocytes in vitro, with potential for use as a promising new antimalarial therapy.

microbiology↗

bioRxiv2023

Investigating Metabolic Trends in the Oral Cavity to Identify Novel Metabolites

The human oral microbiome typically contains over 700 different microbial species. These interactions between the microorganisms within this community can shape the microenvironment throughout the human body, as these interactions are paramount to maintaining oral and overall systemic health. Recent advances in technology, such as next-generation sequencing (NGS), have revealed the complexities of the oral microbiome, linking dysbiosis of the oral microbiome with several chronic ailments such as cardiovascular disease, diabetes, and inflammatory bowel disease. However, the role of microbial secondary metabolites in oral and systemic disease progression remains poorly understood. Here, we conducted a metabolomics study on the human salivary secondary metabolome during the induction of gingival inflammation (gingivitis), the precursor to periodontal disease. In this study, we sought to assess the changes in the oral secondary metabolome during disease progression by emulating dysbiosis of the oral microbiome through a twenty-one-day induction of gingivitis in twenty human participants. We identified secondary metabolites, cyclo(L-Tyr-L-Pro) with regulatory properties for quorum sensing and inflammatory marker secretion, indicating a specialized role for secondary metabolites in oral health maintenance. Surprisingly, we also uncovered a previously unknown metabolic lag that occurs during dysbiosis recovery of the oral cavity, which indicates a lingering presence of signaling molecules for pathogenic microbe proliferation or a total oral metabolome modification following microenvironmental stress in the oral cavity. This work represents a high-resolution metabolomic landscape for understanding oral health during gingivitis that opens new opportunities for combating progressive periodontal diseases and sepsis due to the translocation of oral microbes in the human body.

molecular biology↗

bioRxiv2023

Unique interactions and functions of the mitochondrial small Tims in Trypanosoma brucei

Trypanosoma brucei is an early divergent parasitic protozoan that causes a fatal disease, African trypanosomiasis. T. brucei possesses a unique and essential translocase of the mitochondrial inner membrane, the TbTIM17 complex. TbTim17 associates with 6 small TbTims, (TbTim9, TbTim10, TbTim11, TbTim12, TbTim13, and TbTim8/13). However, the interaction pattern of the small TbTims with each other and TbTim17 are not clear. Here, we demonstrated by yeast two-hybrid (Y2H) analysis that all six small TbTims interact with each other, but stronger interactions were found among TbTim8/13, TbTim9, and TbTim10. Each of the small TbTims also interact directly with the C-terminal region of TbTim17. RNAi studies indicated that among all small TbTims, TbTim13 is most crucial to maintain the steady-state levels of the TbTIM17 complex. Co-immunoprecipitation analyses from T. brucei mitochondrial extracts also showed that TbTim10 has a stronger association with TbTim9 and TbTim8/13, but a weaker association with TbTim13, whereas TbTim13 has a stronger connection with TbTim17. Analysis of the small TbTim complexes by size exclusion chromatography revealed that each small TbTim, except TbTim13, is present in [~]70 kDa complexes, which could be heterohexameric forms of the small TbTims. However, TbTim13 is primarily present in the larger complex (>800 kDa) and co-fractionated with TbTim17. Altogether, our results demonstrated that TbTim13 is a part of the TbTIM complex and the smaller complexes of the small TbTims likely interact with the larger complex dynamically. Therefore, relative to other eukaryotes, the architecture and function of the small TbTim complexes are specific in T. brucei.

cell biology↗

bioRxiv2022

Rapid iPSC inclusionopathy models shed light on formation, consequence and molecular subtype of alpha-synuclein inclusions

Intracellular inclusions accompanying neurodegeneration are histopathologically and ultrastructurally heterogeneous but the significance of this heterogeneity is unclear. iPSC models, while promising for disease modeling, do not form inclusions in a reasonable timeframe and suffer from limited tractability. Here, we developed an iPSC toolbox utilizing piggyBac-based or targeted transgenes to rapidly induce CNS cells with concomitant expression of aggregation-prone proteins. This system is amenable to screening and longitudinal tracking at single-cell and single-inclusion resolution. For proof-of-principle, cortical neuron -synuclein "inclusionopathy" models were engineered to form inclusions through exogenous seeding or -synuclein mutation. These models recapitulated known fibril- and lipid-rich inclusion subtypes, uncovering dynamic interactions between them, and refined the classification of inclusions in postmortem brain. Genetic-modifier and protein-interaction screens pinpointed proteins like RhoA whose sequestration into specific inclusion subtypes is likely to be toxic. This iPSC platform should enhance our understanding of proteinaceous pathologies in neurodegeneration and facilitate therapeutics development.

neuroscience↗

bioRxiv2022

Expression of Microcystis biosynthetic gene clusters in natural populations suggests temporally dynamic synthesis of novel and known secondary metabolites in western Lake Erie

SummaryMicrocystis spp. produces diverse secondary metabolites within freshwater cyanoHABs around the world. In addition to the biosynthetic gene clusters (BGCs) encoding known compounds, Microcystis genomes harbor numerous BGCs of unknown function, indicating its poorly understood chemical repertoire. While recent studies show that Microcystis produces several metabolites in the lab and field, little work has focused on analyzing the abundance and expression of its broader suite of BGCs during cyanoHAB events. Here, we use metagenomic and metatranscriptomic approaches to track the relative abundance of Microcystis BGCs and their transcripts throughout the 2014 western Lake Erie cyanoHAB. Results indicate the presence of several transcriptionally active BGCs that are predicted to synthesize both known and novel secondary metabolites. The abundance and expression of these BGCs shifted throughout the bloom, with transcript abundance levels correlating with temperature, nitrate and phosphorus concentrations, and the abundance of co-occurring predatory and competitive eukaryotic microorganisms, suggesting the importance of both abiotic and biotic controls in regulating expression. This work highlights the need for understanding the chemical ecology and potential risks to human and environmental health posed by secondary metabolites that are produced but unmonitored, as well as the potential discovery of pharmaceutical compounds from cyanoHAB-derived BGCs. Originality-Statement of SignificanceMicrocystis spp. dominate cyanobacterial harmful algal blooms (cyanoHABs) worldwide and pose significant threats to water quality through the production of numerous secondary metabolites, many of which are toxic. While the toxicity and biochemistry of microcystins and several other compounds have been well studied, the broader suite of secondary metabolites produced by Microcystis remains poorly understood, leaving gaps in our understanding of their impacts on ecology, human and ecosystem health, or potential pharmaceutical application. In this study, we use metagenomic and transcriptomic datasets to examine the diversity of genes encoding synthesis of secondary metabolites in natural Microcystis populations and assess their patterns of transcription in the context of biotic and abiotic conditions in western Lake Erie cyanoHABs. Our results reveal the presence of a large diversity of both known gene clusters that encode toxic secondary metabolites as well as novel ones that encode cryptic compounds. This research highlights the need for targeted studies of the secondary metabolite diversity in western Lake Erie, a vital freshwater source to the United States and Canada.

microbiology↗

bioRxiv2022

Distribution of the gyromitrin mycotoxin in the lorchel family assessed by a pre-column-derivatization and ultra high-performance liquid chromatography method

Gyromitrin (acetaldehyde N-methyl-N-formylhydrazone) and its homologs are deadly mycotoxins produced most infamously by the lorchel (also known as false morel) Gyromitra esculenta, which is paradoxically consumed as a delicacy in some parts of the world. There is much speculation about the presence of gyromitrin in other species of the lorchel family (Discinaceae), but no studies have broadly assessed its distribution. Given the history of poisonings associated with the consumption of G. esculenta and G. ambigua, we hypothesized that gyromitrin evolved in the last common ancestor of these taxa and would be present in their descendants with adaptive loss of function in the nested truffle clade, Hydnotrya. To investigate this hypothesis, we developed a sensitive analytical derivatization method for the detection of gyromitrin using 2,4-dinotrobenzaldehyde as the derivatization reagent. In total, we analyzed 66 specimens for the presence of gyromitrin over 105 tests. Moreover, we sequenced the nuc rDNA ITS1-5.8S-ITS2 region (ITS barcode) and nuc 28S rDNA to assist in species identification and to infer a supporting phylogenetic tree. We detected gyromitrin in all tested specimens from the G. esculenta group as well as G. leucoxantha. This distribution is consistent with a model of rapid evolution coupled with horizontal transfer, which is typical for secondary metabolites. We clarified that gyromitrin production in Discinaceae is both discontinuous and more limited than previously thought. Further research is required to elucidate the gyromitrin biosynthesis gene cluster and its evolutionary history in lorchels. KEYWORDS: 2,4-dinitrobenzaldehyde, Gyromitra spp., Hydnotrya spp., Discinaceae, Pezizales, Schiff bases, UHPLC-DAD analysis

biochemistry↗