Biology subjects

Claverol, S.

Publications and source records attributed to Claverol, S..

17 recordsLinked to original sources

bioRxiv2026

Iron exposure reprograms redox homeostasis through mitochondrial depolarization in neuroblastoma

Purpose. Neuroblastoma is the most common malignancy of infancy, and cancer cells strongly depend on iron metabolism for proliferation. Whether sub-cytotoxic iron load reprograms mitochondrial and redox metabolism, and how this relates to the malignant behavior of neuroblastoma cells, is poorly defined. We hypothesized that exposure of human neuroblastoma cells to a non-toxic iron overload perturbs mitochondrial and redox metabolism, thereby affecting cancer cell properties. Methods. SH-SY5Y neuroblastoma cells were exposed to 100 M iron sulfate for 24 h. The resulting changes were monitored using complementary methods, including cell viability, cytotoxicity, proliferation and migration assays, intracellular iron quantification by ICP-MS, confocal imaging of mitochondrial morphology and membrane potential ({Delta}{Psi}m), high-resolution respirometry with flux control ratios, probe-based oxidant and H2O2 measurements, and label-free quantitative proteomics with Ingenuity Pathway Analysis. Results. Non-toxic iron loading raised intracellular iron about four-fold, promoted cell proliferation and reduced migration. Iron induced mitochondrial fragmentation and {Delta}{Psi}m depolarization while preserving mitochondrial content and OXPHOS coupling efficiency. Among respiratory states, only proton-leak respiration increased, paralleled by a higher leak/ETS coupling ratio. Total cellular oxidant levels and H2O2 output were strongly reduced. The proteome showed downregulation of ribosomal proteins and translation/RNA-processing components and upregulation of histones and ferritin. Conclusion. Mild iron exposure reprograms mitochondrial and redox metabolism in neuroblastoma cells. The observed selective increase in proton leak lowers {Delta}{Psi}m to a range that biophysically limits oxidant production while OXPHOS coupling is preserved. Interfering with this adaptive, proton leak-dependent and preventive antioxidant program may offer a way to alter neuroblastoma progression.

biochemistry↗

bioRxiv2026

A lipid droplet triacylglycerol lipase governs neutral lipids mobilization and differentiation of Trypanosoma brucei

Lipid droplets (LD) are dynamic organelles largely distributed in all living cells that are essential notably for membrane biogenesis and cell proliferation. In Trypanosoma brucei, a protozoan parasite responsible for major lethal infectious diseases in humans and cattle, lipid acquisition and mobilization are essential for its survival and adaptation to its different hosts, but the roles of LD in these processes remain largely unknown. To address this gap, we identified and characterized a unique functional orthologue of the human adipose triacylglycerol lipase (ATGL), responsible for the initiation of neutral lipid mobilization, in T. brucei. In this study, we present TbPatatin-like (TbPat), the first ATGL ortholog in protozoan parasites. By combining reverse genetics, microscopy and -omics analysis, we deciphered the role of TbPat in lipolysis and neutral lipid maintenance in both insect and mammalian stages of African trypanosomes and imaged its distribution on the LD surface at an unprecedented resolution by using Cryo-Expansion microscopy. We found that inactivation of TbPat in mammalian form T. brucei led to a global upregulation of the mitochondrial metabolic proteome; furthermore, these cells appeared remarkably unable to differentiate into the procyclic insect stage. Through its expression and localization, TbPat appears to be at an essential checkpoint linking lipid environment and metabolism to more complex cell programs involving proteome, compartment remodeling and lifecycle completion.

microbiology↗

bioRxiv2025

HID1 domain-containing protein 1 is required for normal cell proliferation in Schizosaccharomyces pombe

HID1 domain-containing protein 1 (HID1) is a Golgi apparatus (GA) protein involved in the trafficking of cellular material. From reduced expression in cancer cell lines, it had been proposed to be a tumor suppressor in humans. In contrast, it is required for normal larval development of Caenorhabditis elegans, thereby raising an apparent contradiction for HID1 function regarding the inhibition or maintenance of cell proliferation. An extensive comparison of publicly available gene expression data revealed that HID1 transcript levels in cancer cell lines were not representative of those in primary tumors, and the gene is amplified in many primary tumors. These findings question the role for its expression to suppress cell proliferation. Subsequently, we employed the model S. pombe to explore the role of HID1 in cell proliferation. The knock-out mutant hid1{Delta} exhibited a reduced proliferation phenotype due to a prolonged lag-phase but, eventually, attained parent strain rates of apparent proliferation. RNAseq-based transcriptomics revealed that hid1{Delta} retained features of metabolically stressed cells with quiescence-like transcriptional regulation. A label-free proteomic analysis revealed a lack of various membrane proteins suggesting cells with compromised Golgi apparatus (GA) function. The inability of hid1{Delta} to grow on agar containing a standard minimal medium suggested a link to metabolic deficiency. These findings point to a hid1{Delta}-related perturbation in GA function that compromises cell recovery from metabolic change.

genetics↗

bioRxiv2025

Unveiling the molecular identity of plant autophagic compartments: A proteo-lipidomic study in Arabidopsis thaliana

Autophagy is an intracellular degradation and recycling pathway essential for cell quality control and plant tolerance to stress. The formation and maturation of autophagosomes, the cargo-packing vesicles, rely on extensive membrane remodeling, yet little is known about the nature, dynamics and functions of lipids in these events. Here, we established a method combing cell fractionation and immuno-isolation in native conditions to purify autophagic membranes from Arabidopsis thaliana. By integrating proteomic and lipidomic analyses, we defined their molecular footprint which, coupled to colocalization analyses, revealed potent actors involved in lipid metabolism, membrane trafficking and membrane remodeling, supporting a close interplay between lipid homeostasis and autophagosome biology. Characterization of the phagophore lipid composition showed low sterol and sphingolipid content, a predominance of glycerophospholipids, including phosphoinositides, and a particular enrichment in phosphatidylcholine and phosphatidylglycerol. Comparisons with other plant endomembranes and autophagic compartments from other organisms revealed the singularity of this lipid signature and notably identified phosphatidylglycerol as a plant-specific component of autophagic membranes. Analyses of inducible phosphatidylglycerol-deficient plants showed defects in autophagy activity thereby supporting the functional relevance of the phagophore lipid composition, particularly that of phosphatidylglycerol homeostasis. Together, our findings place lipids as fundamental components of the autophagy molecular landscape and provide a framework to further investigate their contribution to autophagosome biology and functions in plant acclimation to environmental changes. Significance StatementAutophagy is catabolic pathway critical for eukaryotic life and essential for plant acclimation to stress. It hinges on the remarkable plasticity of a specialized membrane, the phagophore, to orchestrate and support intense membrane remodeling events towards the formation of the autophagic vesicle containing cargo. To resolve their elusive molecular bases, we need to integrate inputs from both components of biological membranes: proteins and lipids, yet information regarding lipids is still very limited. Here, we isolated plant phagophores, established their protein and lipid molecular footprint, revealed its singularity and showed its physiological and functional relevance for autophagy activity. Our work highlights lipids as key regulators of plant autophagy and opens new doors for investigating how membrane dynamics shape cellular stress responses.

plant biology↗

bioRxiv2025

Resistance to Atrial Fibrillation Domestication and Mitochondrial Dysfunction in Sheep: a potential key role of the TCA Cycle and mitochondrial redox state

BackgroundAtrial fibrillation (AF) often progresses from paroxysmal to more stable forms. It is well-recognized that patients vary in their AF progression, but underlying mechanisms remain unclear. This work, performed in a sheep AF-model, aimed to identify atrial redox and energetic status differences between animals developing stable AF (AF-S) versus those resistant to AF-stabilization (AF-R). MethodsAF was monitored with telemetry and maintained with bursts of atrial tachystimulation whenever sinus rhythm resumed. Electrophysiological remodeling was assessed via contact mapping. Structural remodeling was described by histology. Proteomic, metabolomic, enzymatic and bioenergetic remodeling were evaluated using frozen left atrial appendage (LAA) tissues and isolated LAA mitochondria. Healthy young rats were used to investigate if an induced metabolic challenge could stabilize AF episodes upon transesophageal atrial tachypacing challenge. ResultsAF-S sheep developed stable AF (>24-hours self-sustained) after 13 days on average, whereas AF-R sheep failed to develop self-sustained AF despite 120 days of electrically-maintained AF. Contact mapping and histological analysis revealed similar electro-structural remodeling in both groups. Metabolic analysis showed significant differences in tricarboxylic acid (TCA) cycle enzymes activities and a 45% increase in AF-S LAA succinate content versus AF-R. AF-S mitochondria showed abnormal mitochondrial succinate oxidation, associated with a significant 20% decrease in ATP synthesis rate, 22% increase in ROS emission and mitochondrial inner membrane hyperpolarization. The ratios of ATP to ADP, NAD+ to NADH, and Complex I/II were disturbed in AF-S compared to AF-R. Calculated mitochondrial NAD+ to NADH ratios suggest a reduced state of in-vivo AF-R mitochondria compared to the oxidized state of AF-S. Exogenous succinate was metabolized when incubated with rat atrial cardiomyocytes and altered redox balance, while intravenous succinate stabilized atrial arrhythmias induced by tachypacing in vivo. ConclusionsSheep resistant to AF-progression showed specific TCA cycle, energetic and redox adaptations compared to animals that developed self-sustained AF. In this animal model, mitochondrial TCA cycle remodeling and associated redox and energetic responses determined the resistance to AF domestication, with potential relevance to identify new mechanistic determinants of AF progression in humans.

pathology↗

bioRxiv2024

A minor impact of VGLUT1 expression level on quantal size revealed through the characterization of VGLUT1mEos2 knock-down new mouse model

Synaptic vesicles (SVs) are small organelles secreting neurotransmitters at synapses. By fusing a photoactivated fluorescent protein to VGLUT1, we generated a VGLUT1mEos2 knock-in mouse. VGLUT1mEos2 knock-in mice are viable and healthy, but exhibit a severe reduction in VGLUT1 expression levels. Using VGLUT1mEos2 expressing neurons, we established paradigms to trace individual SV mobility at the single-molecule level or via massive photoconversion. Hippocampal neurons with significantly diminished VGLUT1 expression maintain unaltered miniature glutamate release characteristics in terms of quantal size and frequency. We demonstrate that VGLUT1 expression level are not correlated in a linear fashion with the vesicular glutamate content. In conclusion, the VGLUT1mEos2 mouse line serves as a powerful tool for exploring SV mobility properties and elucidating the contributions of VGLUT1 to excitatory neurotransmission and cognitive processes.

neuroscience↗

bioRxiv2024

TORC1-dependent control of fission yeast cohesin

Cohesin is a DNA tethering complex essential for chromosome structure and function. In fission yeast, defects in the cohesin loader Mis4 result in chromosome segregation defects and dysregulated expression of genes near chromosome ends. A genetic screen for suppressors of the thermosensitive growth defect of mis4-G1487D identified several hypomorphic mutants of the Target of Rapamycin Complex 1 (TORC1), a conserved kinase that integrates cellular signals to regulate growth and metabolism through substrate-specific phosphorylation. Here, we demonstrate that the TORC1 pathway modulates cohesin functions in chromosome segregation and gene expression. In the context of compromised cohesin loading, the incidence of chromosome segregation defects was modulated by the growth medium in a TORC1-dependent manner. Pharmacological or genetic down-regulation of TORC1 activity restored cohesin binding to its chromosomal sites and improved mitotic chromosome segregation. Notably, reduced TORC1 activity also increased cohesin binding and chromosome transmission fidelity in wild-type cells. These results suggest that environmental cues influence chromosome stability via TORC1. Biochemically, TORC1 co-purified with cohesin and reduced TORC1 activity correlated with decreased phosphorylation of specific residues on Mis4 and cohesin. Mutations in cohesin that mimic the non-phosphorylated state mirrored the effects of TORC1 downregulation, showing that TORC1 is part of the network that controls cohesin phosphorylation to modulate its functions. Finally, we show that the functional interaction between TORC1 and Mis4 extends to the regulation of stress-responsive genes. Our findings reveal a TORC1-cohesin link that may facilitate cellular adaptation to environmental changes. Given that TORC1 inhibitors and calorie restriction extend lifespan in diverse species, this connection raises the intriguing possibility that cohesin-mediated changes in chromosome structure contribute to these effects.

molecular biology↗

bioRxiv2021

Similar neuronal imprint and absence of cross-seeded partner fibrils in α-synuclein aggregates from MSA and Parkinson's disease brains

Aggregated alpha-synuclein (-syn) is a principal constituent of Lewy bodies (LBs) and glial cytoplasmic inclusions (GCIs) observed respectively inside neurons in Parkinsons disease (PD) and oligodendrocytes in multiple system atrophy (MSA). Yet, the cellular origin, the pathophysiological role, and the mechanism of formation of these inclusions bodies (IBs) remain to be elucidated. It has recently been proposed that -syn IBs eventually cause the demise of the host cell by virtue of the cumulative sequestration of partner proteins and organelles. In particular, the hypothesis of a local cross-seeding of other fibrillization-prone proteins like tau or TDP-43 has also been put forward. We submitted sarkosyl-insoluble extracts of post-mortem brain tissue from PD, MSA and control subjects to a comparative proteomic analysis to address these points. Our studies indicate that: i) -syn is by far the most enriched protein in PD and MSA extracts compared to controls; ii) PD and MSA extracts share a striking overlap of their sarkosyl-insoluble proteomes, consisting of a vast majority of mitochondrial and neuronal synaptic proteins, and (iii) other fibrillization-prone protein candidates possibly cross-seeded by -syn are neither found in PD nor MSA extracts. Thus, our results (i) support the idea that pre-assembled building blocks originating in neurons serve to the formation of GCIs in MSA, (ii) show no sign of amyloid cross-seeding in either synucleinopathy, and (iii) point to the sequestration of mitochondria and of neuronal synaptic components in both LBs and GCIs.

neuroscience↗

bioRxiv2020

Sphingolipids mediate polar sorting of PIN2 through phosphoinositide consumption at the trans-Golgi Network

The lipid composition of organelles acts as a landmark to define membrane identity and specify subcellular function. Phosphoinositides are anionic lipids acting in protein sorting and trafficking at the trans-Golgi network (TGN). In animal cells, sphingolipids are known to control the turnover of phosphoinositides through lipid exchange mechanisms at endoplasmic reticulum/TGN contact sites. In this study, we discovered a completely new mechanism acting on sphingolipid-mediated phosphoinositides homeostasis at the TGN in plant cells. We used multi-approaches to show that a reduction of the acyl-chain length of sphingolipid results in increased level of phosphatidylinositol-4-phosphate (PI4P) at the TGN, independently from either lipid exchange induced by sphingolipid synthetic flux, or local PI4P synthesis. Instead, we found that sphingolipids mediate the consumption of PI4P through phosphoinositide-specific phospholipase C (PI-PLC) and this process impacts the sorting of the auxin efflux carrier PIN2 at the TGN. Together, our data identify a new mode of action of sphingolipids in lipid interplay at the TGN during protein sorting.

plant biology↗

bioRxiv2020

Synaptic and supra-synaptic organisation of the dopaminergic projection to the striatum.

Dopamine is a monoamine involved in reward processing and motor control. Volume transmission is thought to be the mechanism by which monoamines modulate effector systems at glutamate and GABA synapses. Hence, dopamine synapses are scarcely described. We applied fluorescence activated synaptosome sorting to explore the features of the dopaminergic synaptome. We provide the proteome of striatal dopaminergic synapses with 57 proteins specifically enriched. Beyond canonical markers of dopamine neurotransmission (Th, Slc6a3/DAT, Slc18a2/VMAT2), we validated 6 proteins belonging to pre- and postsynaptic sides (Cpne7, Apba1/Mint1, Cadps2, Cadm2/SynCAM 2, Stx4 and Mgll). Moreover, dopaminergic varicosities adhere to both a post-synapse with cognate receptors and glutamatergic, GABAergic or cholinergic synapses in structures we named dopaminergic "hub synapses". Markers of presynaptic vesicles and active zone, post-synaptic density and spine apparatus, are significantly increased upon association with dopamine inputs in hubs. Thus neuromodulation frequently operates from hub synapses affecting associated synapses and is not solely dependent on volume transmission. Finally, FASS provides a new framework for the exploration of dopaminergic synapses and more generally for discrete synapse populations ex-vivo. HighlightsO_LIA first proteome of dopaminergic synapses in the striatum C_LIO_LIStriatal dopaminergic synaptosomes display post-synaptic cognate receptors C_LIO_LIDopaminergic projections build hub synapses with excitatory, inhibitory, and cholinergic projections. C_LIO_LICortico-striatal synaptic scaffolds are strengthened upon association in hub synapses. C_LI

neuroscience↗

bioRxiv2020

Emergence of stealth polymorphs that escape α-synuclein amyloid monitoring, take over and acutely spread in neurons

The conformational strain diversity characterizing -synuclein (-syn) amyloid fibrils is possibly at the origin of the different clinical presentations of synucleinopathies. Experimentally, various -syn fibril polymorphs have been obtained from distinct fibrillization conditions by altering the medium constituents and were selected by amyloid monitoring using the probe Thioflavin T (ThT). We report here that besides classical ThT positive products, fibrillization in saline simultaneously gives rise to competing fibril polymorphs that are invisible to ThT (stealth polymorphs), and that can take over. Due to competition, spontaneous generation of such stealth polymorphs bears on the apparent fibrillization kinetics and on the final plateau values. Their emergence has thus been ignored so far or mistaken for fibrillization inhibitions/failures. Compared to their ThT-positive counterparts, and as judged from their chemical shift resonances fingerprint, these new stealth polymorphs present a yet undescribed atomic organization and show an exacerbated propensity (approx. 20-fold) towards self-replication in cortical neurons. They also trigger a long distance synucleinopathic spread along nigro-striatal projections in vivo. In order to rapidly screen fibrillization products for the presence of such stealth polymorphs, we designed a simple multiplexed assay that can be easily and rapidly operated. This assay allows us to demonstrate the sustainability of the conformational replication of these novel and particularly invasive strains. It should also be of help to avoid erroneous upstream interpretations of fibrillization rates based on sole ThT, and to expedite further structural and functional characterization of stealth amyloid assemblies. One Sentence Summarystealth -synuclein fibrils take over

neuroscience↗

bioRxiv2019

Proteomic and metabolomic profiling underlines the stage- and time-dependent effects of high temperature on grape berry metabolism

Climate change scenarios predict an increase in mean air temperatures and in the frequency, intensity, and length of extreme temperature events in many wine-growing regions worldwide. Because elevated temperature has detrimental effects on the berry growth and composition, it threatens the economic and environmental sustainability of wine production. Using Cabernet Sauvignon fruit-bearing cuttings, we investigated the effects of high temperature (HT) on grapevine berries through a label-free shotgun proteomic analysis coupled to a complementary metabolomic study. Among the 2279 proteins identified, 592 differentially abundant proteins were found in berries exposed to HT. The gene ontology categories \"Stress\", \"Protein\", \"Secondary metabolism\" and \"Cell wall\" were predominantly altered under HT. High temperatures strongly impaired carbohydrate and energy metabolism, and the effects depended on the stage of development and duration of treatment. Transcript amounts correlated poorly with protein expression levels in HT berries, highlighting the value of proteomic studies in the context of heat stress. Furthermore, this work reveals that HT alters key proteins driving berry development and ripening. Finally, we provide a list of differentially abundant proteins that can be considered as potential markers for developing or selecting grape varieties that are better adapted to warmer climates or extreme heat waves.

plant biology↗

bioRxiv2018

Cross-linking/Mass Spectrometry: A Community-Wide, Comparative Study Towards Establishing Best Practice Guidelines

The number of publications in the field of chemical cross-linking combined with mass spectrometry (XL-MS) to derive constraints for protein three-dimensional structure modeling and to probe protein-protein interactions has largely increased during the last years. As the technique is now becoming routine for in vitro and in vivo applications in proteomics and structural biology there is a pressing need to define protocols as well as data analysis and reporting formats that are generally accepted in the field and that have shown to lead to high-quality results. This first, community-based harmonization study on XL-MS is based on the results of 32 groups participating worldwide. The aim of this paper is to summarize the status quo of XL-MS and to compare and evaluate existing cross-linking strategies. From the results obtained, common protocols will be established. Our study serves as basis for establishing best practice guidelines in the field for conducting cross-linking experiments, performing data analysis, and reporting formats with the ultimate goal of assisting scientists to generate accurate and reproducible XL-MS results.

biochemistry↗

bioRxiv2018

Multiple C2 domains and Transmembrane region Proteins (MCTPs) tether membranes at plasmodesmata

AO_SCPLOWBSTRACTC_SCPLOWIn eukaryotes, membrane contact sites (MCS) allow direct communication between organelles. Plants have evolved unique MCS, the plasmodesmata intercellular pores, which combine endoplasmic reticulum (ER) - plasma membrane (PM) contacts with regulation of cell-to-cell signalling. The molecular mechanism and function of membrane tethering within plasmodesmata remains unknown.\n\nHere we show that the Multiple C2 domains and Transmembrane region Protein (MCTP) family, key regulators of cell-to-cell signalling in plants, act as ER - PM tethers specifically at plasmodesmata. We report that MCTPs are core plasmodesmata proteins that insert into the ER via their transmembrane region whilst their C2 domains dock to the PM through interaction with anionic phospholipids. A mctp3/4 loss-of-function mutant induces plant developmental defects while MCTP4 expression in a yeast {Delta}tether mutant partially restores ER-PM tethering. Our data suggest that MCTPs are unique membrane tethers controlling both ER-PM contacts and cell-cell signalling.

plant biology↗

bioRxiv2018

Functional recruitment of dynamin requires multimeric interactions for efficient endocytosis

During clathrin mediated endocytosis (CME), membrane scission is achieved by the concerted action of dynamin and its interacting partners. Essential interactions occur between the proline/arginine-rich domain of dynamin (dynPRD) and the Src-homology domain 3 (SH3) of various proteins including amphiphysins. Here we show that multiple SH3 domains must bind simultaneously to dynPRD through three adjacent motifs for dynamins efficient recruitment and function. First, we show in dynamin triple knock-out cells that mutant dynamins modified in a single motif, including the central amphiphysin SH3 (amphSH3) binding motif, are partially capable of rescuing CME. However, mutating two motifs largely prevents that ability. To support this observation, we designed divalent dynPRD-derived peptides. These ligands bind multimers of amphSH3 with >100-fold higher affinity than monovalent ones in vitro. Accordingly, dialyzing living cells with these divalent peptides through a patch-clamp pipette blocks CME 2 to 3 times more effectively than with monovalent ones. Finally, the frequency of endocytic events decreases with competing peptides or hypomorphic rescue mutants but the kinetics of dynamin recruitment is unaffected. This suggests that PRD-SH3 interactions act upstream of dynamin accumulation at the neck of nascent vesicles. We conclude from these data that dynamin drives vesicle scission via multivalent interactions in vivo.

cell biology↗

bioRxiv2018

The Integrative Conjugative Element (ICE) of Mycoplasma agalactiae: key elements involved in horizontal dissemination and influence of co-resident ICEs

The discovery of integrative conjugative elements (ICEs) in wall-less mycoplasmas and the demonstration of their role in massive gene flows within and across species has shed new light on the evolution of these minimal bacteria. Of these, ICEA of the ruminant pathogen Mycoplasma agalactiae represents a prototype and belongs to a new clade of the Mutatorlike superfamily that has no preferential insertion site and often occurs as multiple chromosomal copies. Here, functional genomics and mating experiments were combined to address ICEA functions and define the minimal ICEA chassis conferring conjugative properties to M. agalactiae. Data further indicated a complex interaction among co-resident ICEAs, since the minimal ICEA structure was influenced by the occurrence of additional ICEA copies that can trans-complement conjugative-deficient ICEAs. However, this cooperative behavior was limited to the CDS14 surface lipoprotein, which is constitutively expressed by co-resident ICEAs, and did not extend to other ICEA proteins including the cis-acting DDE recombinase and components of the mating channel whose expression was only sporadically detected. Remarkably, conjugative-deficient mutants containing a single ICEA copy knocked-out in cdsl4 can be complemented by neighboring cells expressing CDS14. This result, together with the conservation of CDS14 functions in closely related species, may suggest a way for mycoplasma ICEs to extend their interaction outside of their chromosomal environment. Overall, this study provides a first model of conjugative transfer in mycoplasmas and offers valuable insights towards the understanding of horizontal gene transfer in this highly adaptive and diverse group of minimal bacteria.\n\nIMPRTANCEIntegrative conjugative elements (ICEs) are self-transmissible mobile genetic elements that are key mediators of horizontal gene flow in bacteria. Recently, a new category of ICEs has been identified that confer conjugative properties to mycoplasmas, a highly adaptive and diverse group of wall-less bacteria with reduced genomes. Unlike classical ICEs, these mobile elements have no preferential insertion specificity and multiple mycoplasma ICE copies can be found randomly integrated into the host chromosome. Here, the prototype ICE of Mycoplasma agalactiae was used to define the minimal conjugative machinery and propose the first model of ICE transfer in mycoplasmas. This model unveils the complex interactions taking place among co-resident ICEs and suggests a way for these elements to extend their influence outside of their chromosomal environment. These data pave the way for future studies aiming at deciphering chromosomal transfer, an unconventional mechanism of DNA swapping that has been recently associated with mycoplasma ICEs.

microbiology↗

bioRxiv2017

H2S mediates interbacterial communication through the air reverting intrinsic antibiotic resistance

Hydrogen sulfide, a gas classically considered as a by-product of cellular metabolism, is today recognized as a crucial gasotransmitter in Eukaryotes. Moreover, most bacteria harbor the eukaryotic orthologous genes for H2S synthesis, and these genes have been linked to different metabolic pathways.\n\nSome bacteria, however, produce high amounts of H2S in their extracellular space, a characteristic classically used for identification purposes. This is the case of Salmonella Typhimurium, which produces H2S by its phsABC operon. Here we show that extracellular release of H2S by S. Typhimurium is solely dependent on its phsABC operon. Furthermore, we show that S. Typhimurium and other H2S-producing bacteria can interact with physically distant bacteria through H2S production. We demonstrate how H2S can revert intrinsic cephalosporin resistance of Enterococccus faecalis and Enterococcus faecium to complete susceptibility. This study constitutes a significant step in the study of bacterial interplay and niche competition. Furthermore, as H2S releasing drugs have already been designed, our results open the way to future therapeutic alternatives for the treatment of infections caused by enterococci, multiresistant pathogens for which no treatments are clinically available.\n\nAuthor SummaryIt has been known for decades that bacteria can communicate with each other through the diffusion of metabolites in the media. However, the capacity of a bacterium to interact with other physically distant cell is a recent discovery of the 21st century. In this work we show how some well-studied bacteria, as it is Salmonella spp., interacts with other bacteria thanks to the compound hydrogen sulfide (H2S) that they produce and release to the environment.\n\nIn our study we have designed novel techniques that allow us to study the interaction between two bacteria, and we have seen that Salmonella is able to affect other species that is even 1 cm away, i.e., a distance corresponding to 10.0000 times its own size.\n\nWhat is more astonishing is that Enterococcus, when exposed to the H2S, is dramatically becomes susceptible to many antibiotics, to which it is supposed to be naturally resistant. Enterococcus spp. are responsible for life-threatening infections in hospitals worldwide. Thus, our observations reveal that bacteria can communicate through the air with H2S, and that this molecule can make bacteria that are highly resistant to antibiotics susceptible to antibiotics, making untreatable infections treatable with current antibiotics.

microbiology↗