Biology subjects

Iatsenko, I.

Publications and source records attributed to Iatsenko, I..

13 recordsLinked to original sources

bioRxiv2026

Microbiota-induced fatty acid synthesis facilitates intestinal infection and immune-mediated damage in Drosophila

The role of the microbiota in facilitating infection is increasingly recognized, though the underlying mechanisms remain under investigation. In this study, we demonstrate that the gut microbiome, particularly Lactiplantibacillus plantarum, promotes enteric infection in Drosophila melanogaster by reshaping host physiology and immune responses. Upon gut colonization, L. plantarum enhances fatty acid (FA) production in the gut. Reducing FA synthesis improves host survival, and pathogen mutants deficient in FA utilization exhibit reduced virulence. FAs support pathogen growth, increase virulence, and enhance resistance to antimicrobial effectors, ultimately facilitating pathogen persistence in the gut. Persisting pathogens consequently overstimulate the immune system, leading to excessive production of antimicrobial peptides (AMPs). Flies lacking AMPs, particularly Metchnikowin and Attacin D mutants, show better survival during infection, implicating AMPs in immunopathology. Our findings identify a mechanism whereby microbiota-induced release of host FAs stimulates pathogen virulence and persistence, ultimately driving AMP-mediated immunopathology.

microbiology↗

bioRxiv2025

A novel enteric pacemaker activity in Drosophila

Enteric organs such as the gut and stomach display the intrinsic ability to generate slow-wave potentials, rhythmic electrochemical events acting as key regulators of gastrointestinal motility. In mammals, slow waves occur as a result of the pacemaker activity of Interstitial Cells of Cajal (ICCs) which, by recruiting visceral muscles, ultimately lead to peristalsis. Here, we uncover and characterize a novel mechanism in Drosophila by which the midgut is able to generate strong muscular whip-like contractions. This pacemaker activity, here named superstalsis, is only active at certain physiological conditions and is selectively linked to longitudinal visceral muscle activation. Furthermore, we identify in Subdued, an ortholog gene of the ANO1/TMEM16A family, a marker for peristalsis in Drosophila, specifically associated with circular muscle activity. As fasting and bacterial infections cause specific changes in the intestinal motility profiles in vivo, we propose that the gut can autonomously alter the peristalsis/superstalsis balance to efficiently respond to diverse pathological and homeostatic events.

physiology↗

bioRxiv2025

A Pore-Forming Toxin Monalysin Contributes to Infection-Induced Suppression of Defecation in Female Drosophila

Pathogen expulsion from the gut via defecation is an important defence strategy against infection. The microbial factors that can subvert this defence reaction remain poorly understood. While many microbes have been found to increase host intestinal peristalsis, Pseudomonas entomophila infection in Drosophila melanogaster leads to infection-induced defecation blockage, particularly in females. Here, we show that this phenotype is driven by a secreted, thermosensitive protein regulated by the GacS/GacA two-component system. Proteomic comparison of the {Delta}gacA mutant, which does not inhibit defecation, and the avirulent {Delta}hfq mutant lacking RNA chaperon Hfq, which still triggers the phenotype, identified pore-forming toxin Monalysin as one of the candidate factors required for inhibiting defecation. Consistently, the Monalysin-deficient mutant was unable to inhibit defecation. Hence, Monalysin besides causing intestinal damage, has a previously unknown role in suppressing defecation and potentially pathogen expulsion. Overall, our study identified a bacterial factor that rapidly reduces defecation frequency, consistent with transient suppression of intestinal transit, thus advancing our understanding of pathogen strategies used to subvert host defences.

microbiology↗

bioRxiv2025

Colonization, translocation, and evolution of opportunistic pathogens during hospital-associated infections

Many commensal bacteria that peacefully reside in the human microbiome are also able to cause acute opportunistic infections. Emerging evidence suggests that within-host evolution contributes to infection, but the genetic mechanisms facilitating the progression of opportunistic pathogens from carriage to acute infection remain unknown. Here, we prospectively collected native samples from four microbiome niches of 13 critically ill patients to assess the evolutionary dynamics leading up to infection. Among three patients we have observed eleven healthcare-associated infections (HAI) caused by nine pathogen species. Leveraging a culture-based approach, we demonstrate that the microbiome is frequently (73%) colonized by the pathogen lineage already before or at the time of diagnosis. Moreover, we identify a short-lived, non-synonymous mutation (F126L) within the fimbriae regulator gene fimZ of Enterobacter hormaechei, first detectable within the gut and subsequently associated with HAI before becoming replaced by body-wide sweeps of independent treatment-associated mutations. Despite fimZ [F126L] being globally undetected, we can show in vitro and in vivo that the F126L mutation leads to elevated biofilm formation, cell adhesion and virulence, suggesting a role during HAI. Our work highlights the power of prospective, population-wide investigation of pathogens to elucidate rapid evolution linked to disease.

microbiology↗

bioRxiv2025

Sex Bias in Iron Sequestration by Transferrin 1 Modulates Sexually-Dimorphic Infection Outcomes in Drosophila melanogaster

Host sexual dimorphism in the outcome of infections is a ubiquitous phenomenon across taxa. However, the immunological differences between males and females and the mechanisms underlying them remain poorly characterized. Here, we used Drosophila melanogaster to test the hypothesis that sex differences in nutritional immunity, particularly iron sequestration, contribute to sexual dimorphism in infection outcome. Using the natural Drosophila pathogen Providencia alcalifaciens, which is controlled by host-mediated iron sequestration, we established an infection model in which males demonstrate increased resistance. Leveraging this model, we demonstrated that males exhibit higher basal and infection-induced expression levels of Transferrin 1-an iron transporter mediating iron sequestration during infection. Consequently, males contained lower iron levels in the hemolymph compared to females. Importantly, sex differences in iron content and in survival after P. alcalifaciens infection were abolished in Tsf1 mutants. However, these mutants still exhibited sex differences in pathogen load. Thus, while Tsf1 mediates sexual dimorphism in iron sequestration and susceptibility to P. alcalifaciens infection, it also has an unexpected role in host tolerance to infection. Finally, we demonstrated that the Toll pathway mediates sex differences in Tsf1 expression and susceptibility to infection. Altogether, our study demonstrates that Tsf1-mediated iron sequestration differs between male and female D. melanogaster, thereby identifying nutritional immunity as a determinant of sexual dimorphism in infection outcome.

immunology↗

bioRxiv2025

Infection-Induced Elevation of Gut Glycosaminoglycans Fosters Microbiota Expansion in Drosophila melanogaster

While host genetics influence the composition of intestinal microbial communities, host genetic factors controlling the abundance of intestinal commensals remain to be determined. Here, we performed a genome-wide association (GWA) study in the fruit fly Drosophila melanogaster to identify host genetic variants linked to the abundance of Lactiplantibacillus plantarum - a major gut commensal of fruit flies. Our GWA study uncovered significant association between polymorphisms in genes involved in heparan sulfate synthesis and L. plantarum load. RNAi mediated knockdown of some of these genes resulted in reduced heparan sulfate synthesis and L. plantarum abundance. Mechanistically, heparan sulfate facilitates adhesion of L. plantarum to host epithelium and promotes biofilm formation. We further showed that infection induces heparan sulfate synthesis by the host via activation of the Nf-kB immune signaling cascade. Increased availability of heparan sulfate during infection results in the expansion of L. plantarum population in the gut and protection of the host from intestinal pathogens via colonization resistance. Furthermore, heparan sulfate is required for infection-induced expression of immune effectors and for prevention of intestinal dysplasia. These findings underscore heparan sulfate as a crucial modulator of intestinal homeostasis, pivotal in microbiota control, intestinal defense, and epithelial renewal.

microbiology↗

bioRxiv2025

Sex Differences in Drosophila Intestinal Metabolism Contribute to Sexually Dimorphic Infection Outcome and Alter Gut Pathogen Virulence

Sexual dimorphism in infection outcomes is a pervasive phenomenon, the underlying mechanisms of which remain incompletely understood. Here, utilizing Pseudomonas entomophila intestinal infection in Drosophila, we demonstrated that sex differences in intestinal redox processes contribute to female bias in susceptibility to gut infection. Female inability to overcome excessive pathogen-induced oxidative stress results in defecation blockage, pathogen persistence, and host death. Male flies exhibit increased carbohydrate metabolism and pentose phosphate pathway activity - a key antioxidant defense system. This allows males to withstand oxidative stress-induced defecation blockage and clear the pathogen from the intestine, resulting in survival. Additionally, P. entomophila showed increased expression of several virulence factors, including RNA-binding protein Hfq, in the female gut, contributing to female-biased virulence of P. entomophila. Thus, the effect of the gut metabolic environment on host defenses and pathogen virulence determines the sex differences in intestinal infection outcomes. HighlightsIntestinal transit of gut pathogen contributes to sexually dimorphic susceptibility to Drosophila gut infection. Male bias in PPP favors pathogen clearance and recovery post-infection. P. entomophila reacts differently to female gut environment, where higher levels of Hfq might contribute to virulence/lethality. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/655590v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@1d6d36borg.highwire.dtl.DTLVardef@d24f2aorg.highwire.dtl.DTLVardef@14b4ed1org.highwire.dtl.DTLVardef@123b46c_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

MprF-mediated immune evasion is necessary for Lactiplantibacillus plantarum resilience in Drosophila gut during inflammation

BackgroundMultiple peptide resistance factor (MprF) confers resistance to cationic antimicrobial peptides (AMPs) in several pathogens, thereby enabling evasion of the host immune response. While MprF has been proven to be crucial for the virulence of various pathogens, its role in commensal gut bacteria remains uncharacterized. To close this knowledge gap, we used a common gut commensal of animals, Lactiplantibacillus plantarum, and its natural host, the fruit fly Drosophila melanogaster, as an experimental model to investigate the role of MprF in commensal-host interactions. ResultsThe L. plantarum {Delta}mprF mutant that we generated exhibited deficiency in the synthesis of lysyl-phosphatidylglycerol (Lys-PG), resulting in increased negative cell surface charge and increased susceptibility to AMPs. Susceptibility to AMPs had no effect on {Delta}mprF mutants ability to colonize guts of uninfected flies. However, we observed significantly reduced abundance of the {Delta}mprF mutant after infection-induced inflammation in the guts of wild-type flies but not flies lacking AMPs. These results demonstrate that host AMPs reduce the abundance of the {Delta}mprF mutant during infection. We found in addition that the {Delta}mprF mutant compared to wild-type L. plantarum induces a stronger intestinal immune response in flies due to the increased release of immunostimulatory peptidoglycan fragments, indicating an important role of MprF in promoting host tolerance to commensals. ConclusionOverall, our results demonstrate that MprF, besides its well-characterized role in pathogen immune evasion and virulence, is also an important resilience factor in maintaining stable microbiota-host interactions during intestinal inflammation.

microbiology↗

bioRxiv2023

The endosymbiont Spiroplasma poulsonii increases Drosophila melanogaster resistance to pathogens by enhancing iron-sequestration and melanization

Facultative endosymbiotic bacteria, such as Wolbachia and Spiroplasma species, are commonly found in association with insects and can dramatically alter their host physiology. Many endosymbionts are defensive and protect their hosts against parasites or pathogens. Despite the widespread nature of defensive insect symbioses and their importance for the ecology and evolution of insects, the mechanisms of symbiont-mediated host protection remain poorly characterized. Here, we utilized the fruit fly Drosophila melanogaster and its facultative endosymbiont Spiroplasma poulsonii to characterize the mechanisms underlying symbiont-mediated host protection against bacterial and fungal pathogens. Our results indicate a variable effect of S. poulsonii on infection outcome, with endosymbiont-harbouring flies being more resistant to Rhyzopus oryzae, Staphylococcus aureus, and Providencia alcalifaciens, but more sensitive or as sensitive as endosymbiont-free flies to the infections with Pseudomonas species. Further focusing on the protective effect, we identified Transferrin-mediated iron sequestration induced by Spiroplasma as being crucial for the defense against R. oryzae and P. alcalifaciens. In case of S. aureus, enhanced melanization in Spiroplasma-harbouring flies plays a major role in the protection. Both iron sequestration and melanization induced by Spiroplasma require the host immune sensor protease Persephone, suggesting a role of proteases secreted by the symbiont in the activation of host defense reactions. Hence, our work reveals a broader defensive range of Spiroplasma than previously appreciated and adds nutritional immunity and melanization to the defensive arsenal of symbionts. ImportanceDefensive endosymbiotic bacteria conferring protection to their hosts against parasites and pathogens are widespread in insect populations. However, the mechanisms by which most symbionts confer protection are not fully understood. Here, we studied the mechanisms of protection against bacterial and fungal pathogens mediated by the Drosophila melanogaster endosymbiont Spiroplasma poulsonii. We demonstrate that besides previously described protection against wasps and nematodes, Spiroplasma also confers increased resistance to pathogenic bacteria and fungi. We identified Spiroplasma-induced iron sequestration and melanisation as key defense mechanisms. Our work broadens the known defense spectrum of Spiroplasma and reveals a previously unappreciated role of melanization and iron sequestration in endosymbiont-mediated host protection. We propose that the mechanisms we have identified here may be of broader significance and could apply to other endosymbionts, particularly to Wolbachia, and potentially explain their protective properties.

microbiology↗

bioRxiv2023

Resistance to host antimicrobial peptides mediates resilience of gut commensals during infection and aging in Drosophila

Resilience to short-term perturbations, like inflammation, is a fundamental feature of microbiota, yet the underlying mechanisms of microbiota resilience are incompletely understood. Here we show that Lactiplantibacillus plantarum, a major Drosophila commensal, stably colonizes the fruit fly gut during infection and is resistant to Drosophila antimicrobial peptides (AMPs). By transposon screening, we identified L. plantarum mutants sensitive to AMPs. These mutants were impaired in peptidoglycan O-acetylation or teichoic acid D-alanylation, resulting in increased negative cell surface charge and higher affinity to cationic AMPs. AMP-sensitive mutants were cleared from the gut after infection and aging-induced gut inflammation in wild-type, but not in AMP-deficient flies, suggesting that resistance to host AMPs is essential for commensal resilience in an inflamed gut environment. Thus, our work reveals that in addition to the host immune tolerance to the microbiota, commensal-encoded resilience mechanisms are necessary to maintain the stable association between host and microbiota during inflammation.

microbiology↗

bioRxiv2022

Lipopolysaccharide-mediated resistance to host antimicrobial peptides and hemocyte-derived reactive-oxygen species are the major Providencia alcalifaciens virulence factors in Drosophila melanogaster

Bacteria from the genus Providencia are ubiquitous Gram-negative opportunistic pathogens, causing "travelers diarrhea", urinary tract, and other nosocomial infections in humans. Some Providencia strains have also been isolated as natural pathogens of Drosophila melanogaster. Despite clinical relevance and extensive use in Drosophila immunity research, little is known about Providencia virulence mechanisms and the corresponding insect host defenses. To close this knowledge gap, we investigated the virulence factors of a representative Providencia species - P. alcalifaciens which is highly virulent to fruit flies and amenable to genetic manipulations. We generated a P. alcalifaciens transposon mutant library and performed an unbiased forward genetics screen in vivo for attenuated mutants. Our screen uncovered 23 mutants with reduced virulence. The vast majority of them had disrupted genes linked to lipopolysaccharide (LPS) synthesis or modifications. These LPS mutants were sensitive to cationic antimicrobial peptides (AMPs) in vitro and their virulence was restored in Drosophila mutants lacking most AMPs. Thus, LPS-mediated resistance to host AMPs is one of the virulence strategies of P. alcalifaciens. Another subset of P. alcalifaciens attenuated mutants exhibited increased susceptibility to reactive oxygen species (ROS) in vitro and their virulence was rescued by chemical scavenging of ROS in flies prior to infection. Using genetic analysis, we found that the enzyme Duox specifically in hemocytes is the source of bactericidal ROS targeting P. alcalifaciens. Consistently, the virulence of ROS-sensitive P. alcalifaciens mutants was rescued in flies with Duox knockdown in hemocytes. Therefore, these genes function as virulence factors by helping bacteria to counteract the ROS immune response. Our reciprocal analysis of host-pathogen interactions between D. melanogaster and P. alcalifaciens identified that AMPs and hemocyte-derived ROS are the major defense mechanisms against P. alcalifaciens, while the ability of the pathogen to resist these host immune responses is its major virulence mechanism. Thus, our work revealed a host-pathogen conflict mediated by ROS and AMPs. Author summaryPathogens express special molecules or structures called virulence factors to successfully infect a host. By identifying these factors, we can learn how hosts fight and how pathogens cause infections. Here, we identified virulence factors of the human and fruit fly pathogen Providencia alcalifaciens, by infecting flies with a series of mutants of this pathogen. In this way, we detected 23 mutants that were less virulent. Some of these less virulent mutants were hypersensitive to fruit fly immune defense molecules called antimicrobial peptides (AMPs), while others were sensitive to reactive oxygen species (ROS) produced by the immune cells. Notably, AMPs-sensitive mutants remained virulent in a Drosophila mutant that lacks AMPs, while pathogens sensitive to oxidative stress retained their virulence in a fruit fly mutant devoid of oxidative species. These results suggest that the ability of P. alcalifaciens to resist two major host immune molecules, namely AMPs and ROS, is the major virulence mechanism. Overall, our systematic analysis of P. alcalifaciens virulence factors has identified the major defense mechanisms of the fruit fly against this pathogen and the bacterial mechanisms to combat these immune responses.

microbiology↗

bioRxiv2020

The Drosophila Baramicin polypeptide gene protects against fungal infection

The fruit fly Drososphila melanogaster combats microbial infection by producing a battery of effector peptides that are secreted into the haemolymph. Technical difficulties prevented the investigation of these short effector genes until the recent advent of the CRISPR/CAS era. As a consequence, many putative immune effectors remain to be characterized and exactly how each of these effectors contributes to survival is not well characterized. Here we describe a novel Drosophila antifungal peptide gene that we name Baramicin A. We show that BaraA encodes a precursor protein cleaved into multiple peptides via furin cleavage sites. BaraA is strongly immune-induced in the fat body downstream of the Toll pathway, but also exhibits expression in the nervous system. Importantly, we show that flies lacking BaraA are viable but susceptible to the enomopathogenic fungus Beauveria bassiana. Consistent with BaraA being directly antimicrobial, overexpression of BaraA promotes resistance to fungi and the IM10-like peptides produced by BaraA synergistically inhibit growth of fungi in vitro when combined with a membrane-disrupting antifungal. Surprisingly, BaraA males but not females display an erect wing phenotype upon infection. Collectively, we identify a new antifungal immune effector downstream of Toll signalling, improving our knowledge of the Drosophila antimicrobial response.

immunology↗

bioRxiv2018

More than black and white: complex relationships involving serine proteases regulate the Toll pathway and the melanization response in Drosophila

The melanization response is a rapid and important defense mechanism in arthropods. Melanin is produced around wound sites and invading microorganisms by phenoloxidases (POs), which need to be activated by the sequential activation of an extracellular serine protease (SP) cascade. Drosophila melanogaster has been a useful genetic model for dissecting insect immune signaling, but understanding these proteolytic cascades has been complicated by the large number of SP genes, possibly with redundant function. Taking advantage of recently-generated null and compound mutants, we re-investigated the role of SPs involved in the melanization response in D. melanogaster and discovered phenotypes previously concealed in single mutant analysis. We found that two of them, Hayan and Sp7, can activate the melanization response in two different manners: Hayan is required in the local blackening of wound sites, while Sp7 regulates an alternate melanization reaction responsible for the clearance of septic infections with Staphylococcus aureus. We present evidence that both Sp7 and Hayan regulate the Toll NF-kB pathway. Sp7 is regulated by canonical Toll signaling downstream of PGRP-SA, ModSP, and Grass, leading to control of septic infections via a Sp7-dependent melanization response. Additionally, we found that Hayan and the Toll-regulating SP Psh are the result of a recent gene duplication. Using genetic manipulations, we reveal the hidden role for Hayan, alongside Psh, in propagating Toll signaling downstream of pattern recognition receptors. Thus, we describe the existence of two pathways leading to the melanization response and reveal previously unknown dynamics in the activation of the Toll pathway.

immunology↗