Biology subjects

Ankri, S.

Publications and source records attributed to Ankri, S..

8 recordsLinked to original sources

bioRxiv2026

Deciphering the Acetaldehyde Signaling Network Underlying Bacterial Escape from Protozoan Predators

Entamoeba histolytica (Eh) is a formidable intestinal pathogen, yet the ecological principles governing its invasion of the gut microbiome remain elusive. Upon colonization, Eh encounters resident bacteria typically sequestered within aggregates and biofilms. While Eh utilizes cysteine proteinases to degrade biofilm matrices and access bacterial prey, the strategies bacteria employ to sense and evade this predation are largely unknown. Here, we identify a metabolic signalling axis that allows the probiotic bacterium Bacillus subtilis to perceive and respond to predatory Eh. In the absence of mitochondria, Eh relies on fermentative glycolysis, using alcohol dehydrogenase to produce distinct metabolic byproducts. Using quantitative proteomics and single-cell imaging, we demonstrate that B. subtilis detects the Eh-derived metabolite acetaldehyde as a proxy for predator presence. By mapping the acetaldehyde-responsive regulatory network, we show how this metabolic input is transduced to control the motility machinery, while our data suggest that the broader predatory secretome acts as a multi-modal signal influencing multiple bacterial physiological programs. This chemical cue triggers a rapid phenotypic switch in B. subtilis, driving a transition towards a motile, planktonic "flight" response. Our findings reveal that commensal bacteria exploit the unique metabolic signature of anaerobic parasites to coordinate defensive behaviours, highlighting how inter-kingdom signalling shapes microbiome architecture during infection.

microbiology↗

bioRxiv2025

The gut microbiota-derived metabolite indole regulates cytoskeletal functions and virulence in Entamoeba histolytica

Entamoeba histolytica is a pathogenic amoeba that inhabits the human large intestine and causes amoebiasis. E. histolytica interacts with both the intestinal microbiota and the metabolites they produce. These bacterial metabolites play a crucial role in shaping the virulence and stress resistance of E. histolytica. One such metabolite, indole, is synthesized by bacteria from tryptophan and functions as a key signaling molecule. In this study, we investigated the impact of indole on E. histolytica by incubating trophozoites with the metabolite and performing proteomic analyses under various conditions, including trophozoites adapted to indole. Our results show that indole is toxic to E. histolytica, with an inhibitory concentration (IC) of 1.2 mM; however, the parasite can adapt to this concentration. Proteomic analyses reveal that indole-adapted trophozoites display enhanced resistance to oxidative stress (OS), upregulation of cytoskeletal proteins, and increased virulence. These trophozoites exhibit increased F-actin formation, smaller cell size, stronger adhesion to HeLa cells, enhanced migratory capacity, and more effective colonization of the mouse cecum compared to non-adapted trophozoites. Thus, indole exerts a dual effect on E. histolytica physiology. While indole is initially toxic to the parasite, adaptation to indole confers enhanced resistance to OS and promotes a more virulent phenotype. This duality underscores the complex role of microbiota-derived metabolites in modulating parasite behavior and highlights indole as a key microbial signal. Author summaryEntamoeba histolytica is a unicellular parasite living in the human large intestine and can cause a disease called amoebiasis. Inside the intestine, E. histolytica interacts with the microbiota and with the metabolites they produce. One such metabolite is indole, which is produced by gut bacteria from tryptophan and used by human cells and trophozoites. In this study, we explored how indole affects E. histolytica. We found that indole is toxic to the parasite at first, but over time, the amoeba can adapt and survive in its presence. Using protein analysis techniques, we discovered that indole-adapted amoebas become more resistant to stress and more virulent. They produce more F-actin, leading to improved mobility, degrade more HeLa cells, and colonize the gut of mice more efficiently than wild-type amoebas (WT). These results show that, while indole initially harms the parasite, it also triggers changes that make it more resistant to stress and more virulent. Our work highlights how metabolites produced by bacteria in the large intestine can influence the behavior of E. histolytica.

microbiology↗

bioRxiv2024

Differential coping strategies exerted by biofilm and planktonic cells of the beneficial bacterium B. subtilis in response to the protozoan predator Entamoeba histolytica.

The human protozoan parasite Entamoeba histolytica causes amebiasis and interacts with both beneficial and harmful members of the microbiome. In previous studies, it was shown that E. histolytica can break down pre-established biofilms of B. subtilis in a time- and dose-dependent manner. Inhibiting parasitic cysteine proteases impairs biofilm degradation. However, it is still unknown whether bacteria can sense this process and respond to the degradation of the biofilms. Here, our research demonstrates a multi-layered response of probiotic bacteria to the parasite, which differs between planktonic bacteria and pre-established biofilms. Sensing the activity of cysteine proteases from E. histolytica, the bacteria activate the general stress response and, to a lesser extent, the cell wall stress response, making the surviving biofilm members more resistant to mild stressors. On the other hand, planktonic cells exposed to the predators lysate deactivate the expression of genes associated with biofilm formation while inducing their motility to avoid predation. Overall, our results indicate that bacteria have evolved to recognize amoeba predators. Furthermore, the partially digested biofilm cells may have unexpected disadvantages over bacteria that did not encounter a predator. These findings may be useful in developing more efficient probiotic strains that are resilient to amoebiasis.

microbiology↗

bioRxiv2024

Enteropathogenic Escherichia coli induces Entamoeba histolytica Levy-like movement on fibronectin-rich substrate by reducing traction forces

Amebiasis, caused by Entamoeba histolytica, is a global health concern, affecting millions and causing significant mortality, particularly in areas with poor sanitation. Although recent studies have examined E. histolyticas interaction with human intestinal microbes, the impact of bacterial presence on the parasites motility, mechanical forces, and their potential role in altering invasiveness have not been fully elucidated. In this study, we utilized a micropillar-array system combined with live imaging to investigate the effects of enteropathogenic Escherichia coli on E. histolyticas motility characteristics, F-actin spatial localization, and traction force exerted on fibronectin-coated substrates. Our findings indicate that co-incubation with E. coli significantly enhances the motility of E. histolytica, as evidenced by the enhancement of Levy-like movement patterns, i.e., increased directionality and velocity. This increased motility is accompanied by a reduction in F-actin-dependent traction forces and podosome-like structures on fibronectin-coated substrates, but with increased F-actin localization in the upper part of the cytoplasm. These findings highlight the role of physical interactions and cellular behaviors in modulating the parasites virulence, providing new insights into the mechanistic basis of its pathogenicity. Author SummaryAmebiasis, caused by the protozoan parasite Entamoeba histolytica, is a major global health issue, affecting around 50 million people and resulting in 100,000 deaths annually. The disease is transmitted through contaminated food and water. Upon reaching the intestines, which are teeming with bacteria, E. histolytica begins its invasion by removing the protective mucus layer, followed by adhering to and detaching enterocytes, leading to the disruption and degradation of the epithelial barrier. Afterwards, E. histolytica invades along the fibronectin-rich basement membrane deep into the crypts of Lieberkuhn, eventually penetrating the fibronectin- rich lamina propria. This leads to further tissue destruction and potential dissemination to distant organs, causing severe complications. In our study, we explored how the presence of enteropathogenic bacteria affects the parasites motility and mechanical force generation, both of which are key to its pathogenicity. Using a micropillar-array system and live imaging, we found that exposure to enteropathogenic Escherichia coli significantly increases E. histolyticas motility while reducing its traction force on fibronectin-rich matrices. These changes in behavior highlight the role of bacterial interactions in enhancing the parasites virulence. Our findings provide important insights into the mechanistic basis of E. histolyticas pathogenicity, offering potential avenues for new treatments against amebiasis.

microbiology↗

bioRxiv2022

Digestive exophagy of Bacterial Biofilms by an Amoeba Predator is Mediated by Specific Biofilm Recognition

The human protozoan parasite Entamoeba histolytica is responsible for amebiasis, a disease endemic to developing countries. E. histolytica trophozoites are released from the cysts to colonize the large intestine, where they primarily feed on bacterial cells. In these scenarios, bacterial cells form aggregates or structured communities too large for phagocytosis. Our results show that E. histolytica can degrade pre-established biofilms of Bacillus subtilis and Escherichia coli in a dose- and time-dependent manner. Surprisingly, trophozoites incubated with B. subtilis biofilm exhibit a unique transcriptome signature compared to those incubated with planktonic cells or without bacteria. Biofilm-induced genes include cysteine proteases (CPs), and the general inhibition of CPs by E64D or by the use of specific small-RNA (sRNA)-based RNA interference impairs the degradation of biofilms by E. histolytica. The degradation of B. subtilis extracellular matrix (ECM) protein TasA by CPs is associated with partial biofilm digestion and activation of the stress response in the interacting B. subtilis cells. The interaction with B. subtilis biofilms was also associated with lower levels of oxidoreductases. Oxidoreductase downregulation can be a readout of the embedding of E. histolytica trophozoites within the biofilm-produced extracellular matrix, reducing their exposure to oxidative stress (OS). Our results indicate that parasites may digest biofilms by a controlled mechanism of digestive exophagy as secretion of digestive enzymes as a conserved mechanism for biofilm degradation allows phagocytic digestion of biofilm cells. Furthermore, the partially digested biofilms can serve as an unexpected shield protecting parasites from oxidative environments and thereby may regulate the persistence and virulence of the parasite.

microbiology↗

bioRxiv2022

Queuine salvaging in the human parasite Entamoeba histolytica

Queuosine (Q) is a naturally occurring modified nucleoside that occurs in the first position of transfer RNA anticodons such as Asp, Asn, His, and Tyr. As eukaryotes lack pathways to synthesize queuine, the Q nucleobase, they must obtain it from their diet or gut microbiota. Previously, we described the effects of queuine on the physiology of the eukaryotic parasite Entamoeba histolytica and characterized the enzyme EhTGT responsible for queuine incorporation into tRNA. At present, it is unknown how E. histolytica salvages Q from gut bacteria. We used liquid chromatography-mass spectrometry (LC-MS) and N-acryloyl-3-aminophenylboronic acid (APB) PAGE analysis to demonstrate that E. histolytica trophozoites can salvage queuine from Q or E. coli K12 but not from the modified E. coli QueC strain, which cannot produce queuine. We then examined the role of EhDUF2419, a protein with homology to DNA glycosylase, as queuine salvage enzyme in E. histolytica. We found that glutathione S-transferase (GST)-EhDUF2419 catalyzed the conversion of Q into queuine. Trophozoites silenced for EhDUF2419 expression are impaired in their ability to form Q-tRNA from Q or from E. coli. We also observed that Q partially protects control trophozoites from oxidative stress (OS), but not siEhDUF2419 trophozoites. Overall, our data reveal that EhDUF2419 is central for the salvaging of queuine from bacteria and for the resistance of the parasite to OS.

microbiology↗

bioRxiv2021

Entamoeba histolytica adaption to auranofin: a phenotypic and multi-omics characterization

Auranofin (AF), an antirheumatic agent, targets mammalian thioredoxin reductase (TrxR), an important enzyme controlling redox homeostasisis, AF is also very effective against a diversity of pathogenic bacteria and protozoan parasites. Here, we report about the resistance of the parasite Entamoeba histolytica to 2 M of AF that has been acquired by gradual exposure of the parasite to increasing amount of the drug. AF adapted E.histolytica trophozoites (AFAT) has an impaired growth, cytopathic activity and they are more sensitive to oxidative stress (OS), nitrosative stress (NS) and metronidazole (MTZ) than wild type (WT) trophozoites. Integrated transcriptomics and redoxomics analyses showed that many upregulated genes in AFAT, including genes encoding for dehydrogenase and cytoskeletal proteins, have their product oxidized in wild type trophozoites exposed to AF (acute AF trophozoites) but not in AFAT. We also showed that the level of reactive oxygen species (ROS) and oxidized proteins (OXs) in AFAT is lower than that of acute AF trophozoites. Overexpression of E.histolytica TrxR (EhTrxR) did not protect the parasite against AF which suggests that EhTrxR is not central is the mechanism of adaptation to AF.

microbiology↗

bioRxiv2020

Queuine is a nutritional regulator of Entamoeba histolytica response to oxidative stress and a virulence attenuator

Queuosine is a naturally occurring modified ribonucleoside found in the first position of the anticodon of the transfer RNAs for Asp, Asn, His and Tyr. Eukaryotes lack pathways to synthesize queuine, the nucleobase precursor to queuosine, and must obtain it from diet or gut microbiota. Here we describe the effects of queuine on the physiology of the eukaryotic parasite, Entamoeba histolytica, the causative agent of amebic dysentery. Queuine is efficiently incorporated into E. histolytica tRNAs by a tRNA-guanine transglycosylase (EhTGT) and this incorporation stimulates the methylation of C38 in tRNAAspGUC. Queuine protects the parasite against oxidative stress (OS) and antagonizes the negative effect that oxidation has on translation by inducing the expression of genes involved in OS response, such as heat shock protein 70 (Hsp 70), antioxidant enzymes, and enzymes involved in DNA repair. On the other hand, queuine impairs E. histolytica virulence by downregulating the expression of genes previously associated with virulence, including cysteine proteases, cytoskeletal proteins, and small GTPases. Silencing of EhTGT prevents incorporation of queuine into tRNAs and strongly impairs methylation of C38 in tRNAAspGUC, parasite growth, resistance to OS, and cytopathic activity. Overall, our data reveal that queuine plays a dual role in promoting OS resistance and reducing parasite virulence. ImportanceEntamoeba histolytica is a unicellular parasite that causes amebiasis. The parasite resides in the colon and feeds on the colonic microbiota. The gut flora is implicated in the onset of symptomatic amebiasis due to alterations in the composition of the bacteria. These bacteria modulate the physiology of the parasite and affect the virulence of the parasite through unknown mechanisms. Queuine, a modified nucleobase of queuosine, is exclusively produced by the gut bacteria and leads to tRNA modification at the anticodon loops of specific tRNAs. We found that queuine induces a mild oxidative stress resistance in the parasite and attenuates its virulence. Our study highlights the importance of bacterially derived products in shaping the physiology of the parasite. The fact that queuine inhibits the virulence of E. histolytica may lead to new strategies for preventing and/or treating amebiasis by providing to the host queuine directly or via probiotics.

microbiology↗