Biology subjects

Gauthier, C.

Publications and source records attributed to Gauthier, C..

16 recordsLinked to original sources

bioRxiv2026

Coronary artery disease is linked with demyelination and iron deposition in white matter watershed areas

Coronary artery disease increases risk of cognitive decline and stroke and is associated with white matter alterations. However, the biological basis of these changes remains unclear. Myelin content and iron deposition are crucial measures of white matter health and can be measured with quantitative MRI. This study investigated whether myelin and iron alterations occur in coronary artery disease, and their relationship with cognition. In this cross-sectional study, 46 individuals with coronary artery disease and 40 healthy controls aged > 50 years, with normal cognition underwent 3T MRI and cognitive assessments. Quantitative MRI metrics (susceptibility, magnetization transfer saturation, R2* and R1 relaxation rates) were calculated in the border zones between adjacent arterial territories (watershed regions) and in the areas outside these borders (non-watershed regions). Relative to controls, the coronary artery disease group showed lower myelin and higher iron content, as measured by lower magnetization transfer saturation and R1, and higher susceptibility specifically in watershed regions. Importantly, these microstructural alterations were associated with poorer cognitive performance in the coronary artery disease group with lower magnetization transfer and R1related to poorer global cognition and with higher magnetic susceptibility with poorer verbal memory. These findings suggest that coronary artery disease is associated with demyelination and iron deposition in white matter, most prominently in watershed regions, which are known for their susceptibility to stroke. The association of these microstructural alterations with cognition highlights the role of white matter as a key vulnerable region and a promising focus for future mechanistic and therapeutic studies.

neuroscience↗

bioRxiv2026

L1CAM-CAR T cells with enhanced potency overcome low-density antigen expression in rhabdomyosarcoma

Rhabdomyosarcoma (RMS), the most common pediatric soft tissue sarcoma, shows dismal survival in relapsed or metastatic alveolar disease. Chimeric antigen receptor (CAR) T cells are promising but limited by scarce tumor-selective antigens and suboptimal efficacy at low antigen density. We investigated L1 cell adhesion molecule (L1CAM) as a therapeutic target by profiling its expression by flow cytometry, immunoblotting, and immunohistochemistry in cell lines, patient-derived xenografts, and healthy tissues. Using the scFv derived from the CE7 antibody, we engineered L1CAM-CARs with distinct hinge and costimulatory domains and tested them in vitro and in orthotopic RMS mouse models against clinically tested CE7- and B7-H3-CARs. L1CAM was consistently expressed at moderate levels in RMS, especially alveolar subtypes, but very weakly expressed in healthy tissues. Flow cytometry revealed a moderate density typically limiting CAR activity. Among constructs, L1CAM.III (CE7-CAR with long hinge and CD28 domain) showed the strongest cytotoxicity and IFN-{gamma} release. In vivo, L1CAM.III-CAR T cells regressed tumors, prolonged survival, and persisted in orthotopic RMS models, showing greater efficacy in alveolar RMS and no off-tumor activity. These findings establish L1CAM as a rational RMS therapeutic target. Optimized L1CAM.III-CAR T cells overcome moderate antigen density, achieving potent and persistent antitumor activity comparable to B7-H3-CARs but with improved safety. This work supports CAR optimization for clinical translation to broaden pediatric sarcoma immunotherapy.

cancer biology↗

bioRxiv2026

Implantation failure linked to altered uterine NK cells in PCOS-like mice

Uterine NK (uNK) cells are essential for reproductive function, yet little is known how they are affected in polycystic ovary syndrome (PCOS), despite the strong association between PCOS and reproductive complications. We demonstrate that implantation failure coincides with distinct phenotypic alterations of uNK cells in a PCOS-like mouse model. Hyperandrogenism caused an increased influx of conventional NK (cNK) cells into the uterus, which contributed to an augmented uNK cell population, while tissue-resident NK (trNK) cells remained unchanged. Notably, CD69+ trNK cells were reduced and seemingly compensated by an upregulated expression of CD69 on cNK cells in the uterus. The maturation of uNK cells was disrupted and plausibly linked to an inability of cNK cells to convert into trNK cells. The inhibited maturation was associated with a reduced expression of the inhibitory receptor NKG2A, demonstrating an impaired education of uNK cells. This disruption of uNK cells could contribute to endometrial dysfunction and may be an underlying factor to reproductive comorbidities such as implantation failure, miscarriage and pre-eclampsia in PCOS.

immunology↗

bioRxiv2025

Pantoea ananatis-triggered systemic resistance requires root sensing through the LORE receptor kinase in Arabidopsis

Systemic immunity induced by beneficial bacteria helps plants to cope with subsequent pathogen attacks. However, how these bacteria are sensed by plants and how this sensing results in a systemic response is not well understood. Recently, the Brassicaceae LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (LORE) receptor kinase was identified as the direct sensor of bacterial medium-chain-length 3-hydroxy fatty acids (mc-3-OH-FAs) and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs), which activate systemic Brassicaceae immunity. Here, we show that the bacterium Pantoea ananatis BRT175, which produces HAAs, can colonize Arabidopsis thaliana roots independently of the production of these compounds. P. ananatis triggers induced systemic resistance (ISR) to the necrotrophic pathogen Botrytis cinerea, but not to the hemibiotrophic pathogen Pseudomonas syringae pv. tomato. Importantly, this ISR can be mimicked by HAAs or 3-hydroxy-decanoic acid (3-OH-C10). Both P. ananatis-triggered and 3-OH-C10-triggered ISR against B. cinerea are mediated by LORE sensing, involve salicylic acid, jasmonic acid and ethylene signaling pathways, and activate the expression of similar defense genes in infected leaves. Thus, 3-OH-C10 and HAAs are perceived by a pattern recognition receptor (PRR) in the root and activate a local immune response in roots as well as systemic immunity in leaves. Our study demonstrates that these lipidic microbe-associated molecular patterns (MAMPs), produced by beneficial microorganisms, are necessary and sufficient to trigger rhizobacteria-driven ISR. It further highlights the role of these MAMPs in differentially activating systemic resistance against biotrophic and necrotrophic pathogens.

plant biology↗

bioRxiv2025

Reduced cerebrovascular reactivity is more pronounced in female than male youth with complex congenital heart defects

AimsCongenital heart defects (CHD) are the most common neonatal malformations. Neonates with complex CHD present with cerebrovascular dysfunction, including deficits in cerebrovascular reactivity (CVR), a measure of vascular reserve. However, it is unknown whether these deficits persist beyond the perioperative period. Methods and ResultsHere, we compared CVR between 53 youth with CHD and 54 age-matched controls without CHD. CVR was derived using a novel approach based on resting state blood oxygen-level dependent magnetic resonance imaging. We found that youth with CHD present with relative CVR deficits in the whole gray matter and in the anterior cerebral artery territory when compared to controls. Sex differences were identified in the middle cerebral artery territory, with females having lower relative CVR than males in the CHD group. Greater CVR deficits were observed in individuals with single-ventricle as compared to participants with a two-ventricle physiology. Finally, in the CHD group, a lower CVR was found to be associated with reduced performance on the Metacognitive Abilities Index of the BRIEF-A. ConclusionThese results indicate that cerebrovascular deficits in CHD survivors persistent into young adulthood and that CVR offers great promise as a biomarker of cerebrovascular health which could be targeted in future interventions.

neuroscience↗

bioRxiv2025

Greater cardiorespiratory fitness is associated with higher cerebral blood flow and lower oxygen extraction fraction in healthy older adults

Aerobic exercise training promotes cardiovascular, brain and cognitive health. Regular exercise is associated with higher cardiorespiratory fitness, commonly assessed by peak oxygen uptake (VO2peak) during maximal effort testing. Higher cardiorespiratory fitness has been linked to preserved brain health, particularly higher grey matter volume and perfusion. The brain relies heavily on oxidative metabolism, yet the relationship between cardiorespiratory fitness and brain oxidative metabolism remains underexplored. This study investigated the association between VO2peak and two key cerebral metabolic parameters: the cerebral metabolic rate of oxygen consumption (CMRO2) and oxygen extraction fraction (OEF), which represents the balance between cerebral blood flow (CBF) and CMRO2. Thirty-seven healthy adults aged [≥]50 underwent maximal cardiopulmonary exercise testing for VO2peak assessment. Neuroimaging included dual calibrated functional MRI (dc-fMRI) and quantitative susceptibility mapping (QSM). Higher VO2peak correlated positively with higher CBF across whole-brain grey matter but showed no relationship with CMRO2. Conversely, higher VO2peak negatively correlated with lower OEF from both dc-fMRI and QSM. These findings suggest that greater cardiorespiratory fitness enhances cerebral perfusion without changing resting metabolic rate in healthy older adults, resulting in a reduced oxygen extraction. These results are consistent with exercise yielding improved vascular- metabolic coupling, which would reduce the likelihood of transient hypoxic episodes.

biophysics↗

bioRxiv2025

Preservation of cerebral vascular and metabolic health with greater cardiorespiratory fitness in coronary artery disease

BackgroundCoronary artery disease (CAD) is the leading cause of cardiovascular-related death globally. Beyond its cardiac consequences, CAD significantly impacts brain health, causing grey matter atrophy, reduced cerebral blood flow (CBF), impaired cerebrovascular reactivity (CVR), and cognitive decline. Recent evidence also highlights altered cerebral metabolism in CAD, characterized by reduced cerebral metabolic rate of oxygen consumption (CMRO2) and increased oxygen extraction fraction (OEF). Notably, impaired cardiorespiratory fitness, as measured by reduced peak oxygen uptake (VO2peak), is a hallmark of CAD progression and a strong prognostic marker of cardiovascular and neurological outcomes. Although VO2peak is associated with brain structural integrity and cognitive function, its relationship to cerebral vascular and metabolic function in CAD patients remains poorly understood. MethodsThirty-seven healthy individuals (age=65.35 {+/-} 8.31) and thirty-five patients with CAD (age=66.42 {+/-} 9.29) participated in this study. The objective was to determine whether higher cardiorespiratory fitness is associated with markers of cerebral health known to be impaired in CAD, in order to assess the potential of exercise as a strategy to mitigate CAD-related brain alterations. Cerebral vascular and metabolic biomarkers, including CBF, CVR, CMRO2, and OEF, were quantified using calibrated functional magnetic resonance imaging (MRI). Participants also completed a maximal cardiopulmonary exercise test on a bicycle ergometer to determine peak oxygen uptake (VO2peak). ResultsAcross all participants, VO2peak was positively associated with CBF ({beta}=0.32, p=0.02), and CVR ({beta}=0.002, p=0.04), in grey matter, confirming a link between aerobic fitness and vascular health across the cardiovascular health spectrum. However, metabolic markers exhibited group-specific patterns. Specifically, in CAD patients, VO2peak was positively associated with CMRO2 ({beta} = 0.08, p = 0.02), suggesting that reduced CMRO2 in CAD may be partially preserved by greater cardiorespiratory fitness. In contrast, a negative association between VO2peak and OEF was observed exclusively in healthy controls ({beta} = -3.6, p = 0.02), consistent with adaptations in healthy aging being primarily driven by improved CBF without changes in CMRO2. ConclusionThis study shows that higher cardiorespiratory fitness is associated with improved cerebral vascular and metabolic function, with distinct patterns observed between healthy individuals and those with CAD. In patients with CAD, greater fitness appears to preserve cerebral oxygen metabolism, while in healthy individuals, fitness is primarily linked to enhanced perfusion. These findings support the role of aerobic exercise as a promising strategy to counteract CAD-related brain alterations, emphasizing the importance of targeting cardiorespiratory fitness in both prevention and rehabilitation settings.

biophysics↗

bioRxiv2025

The Impact of Coronary Artery Disease on Brain Vascular and Metabolic Health: Links to Cognitive Function

BackgroundCoronary artery disease (CAD) is the leading cause of mortality worldwide and is associated with an increased incidence of cognitive decline, however the pathological mechanisms linking CAD to brain and cognitive health remain unclear. Prior research has identified regional deficits in cerebral blood flow (CBF) and cerebrovascular reactivity (CVR), a measure of vascular reserve, in patients with CAD. However, the impact of these cerebrovascular deficits on cognition has not been explored, nor has the effect of CAD on cerebral metabolic health. This study aims to fill these gaps by investigating how CAD influences cerebral vascular and metabolic health, and how these alterations relate to cognitive function across multiple domains. MethodsQuantitative magnetic resonance imaging (MRI) was employed to measure a comprehensive profile of cerebral vascular and metabolic health, including CBF, CVR, cerebral metabolic rate of oxygen (CMRO2), and oxygen extraction fraction (OEF). Cognition was assessed using a validated neuropsychological battery from which composite scores were extracted, reflecting executive functions, working memory, processing speed, and verbal episodic memory. ResultsA total of 35 patients with CAD and 37 healthy controls were included in the final analysis. Patients with CAD demonstrated widespread impairments in both cerebral vascular and metabolic health, characterized by lower CBF, CVR, and CMRO2, and increased OEF, indicative of insufficient oxygen delivery. Notably, lower CVR was associated with poorer executive function, suggesting a specific role of vascular reserve for preserving executive functions. Furthermore, higher OEF was associated with poorer working memory, showing the importance of preserved oxygen consumption for maintaining cognitive function. ConclusionThis study reveals that CAD is associated with impaired cerebral vascular and metabolic health, providing a pathological basis for cognitive decline. Specifically, reduced CVR and elevated OEF emerged as sensitive biomarkers linking impaired brain health and cognition. These markers hold promise for guiding future interventions aimed at preserving cognitive health in patients with CAD. Clinical PerspectiveO_ST_ABSWhat Is New?C_ST_ABSO_LICoronary artery disease is associated with an increased incidence of cognitive decline but the biological mechanisms underlying these changes in cognition are unclear. C_LIO_LIThis is the first study to comprehensively demonstrate profound and widespread deficits in both cerebral vascular and oxidative metabolic health in patients with coronary artery disease. C_LIO_LICerebrovascular reactivity and oxygen extraction fraction may be sensitive biomarkers of early cognitive decline in coronary artery disease. C_LI What Are the Clinical Implications?O_LIThe widespread impairments in cerebral vascular and metabolic health suggest that coronary artery disease has profound consequences on the brain. C_LIO_LIPoor vascular reserve and an imbalance between oxygen delivery and usage may be crucial determinants of cognitive health. These results highlight the limitations of traditional biomarkers in understanding the brains vulnerability and the need for these novel and quantitative biomarkers of cerebral physiological health. C_LIO_LIThese findings suggest that cerebral vascular and metabolic deficits exist even in the absence of overt cognitive decline in coronary artery disease, emphasizing the need for early detection and preventative strategies. C_LI

biophysics↗

bioRxiv2025

LHR and Gαs trafficking drive sustained cAMP signalling from endosomes to control steroidogenesis

1.A growing number of G protein-coupled receptors (GPCRs) signal through G proteins from intracellular compartments following endocytosis. While for few receptors the physiological relevance of such mechanism has been established, the relationships between the spatio-temporal organization of cellular signalling and the physiological responses are still to be elucidated for most receptors. Signalling by the luteinizing hormone receptor (LHR) is essential to regulate sex steroids production in gonads, but how G protein-dependent signals from endosomes are functionally important for steroidogenesis remains unexplored. Here, we demonstrate that transient LHR activation promotes a prolonged Gs/cAMP signalling from endosomes, which requires ligand-induced independent receptor and Gs trafficking. We show that endosomal trafficking is specifically required for ligand-induced cAMP accumulation in the nucleus and gene expression, as well as for steroids production in Leydig cells. Thus, this study contributes to further understand the molecular mechanisms by which LHR, through signalling compartmentalization, controls gonadal steroidogenesis.

cell biology↗

bioRxiv2025

A single domain intrabody as a novel tool to bias the subcellular trafficking of the follicle-stimulating hormone receptor

Intracellular variable fragments from heavy-chain only antibodies of camelids (intra-VHH) have been successfully used for their stabilizing properties to solve the 3D structure of active G protein-coupled receptors (GPCRs) bound to their cognate transducers. They also provide tools to link a given conformation of a GPCR to the signalling network engaged, thus allowing extensive structure/activity studies. Recently, they have been instrumental in tracking active GPCRs in various subcellular compartments. Here, we report the isolation and characterization of iPRC2, an intra-VHH recognizing the 1st and 3rd intracellular loops of the FSHR, but not of the luteinizing hormone/choriogonadotropin receptor close relative. Its expression in the cell decreases the cAMP production in response to hormone binding, and requires Gs for optimal interaction with the receptor. Importantly, iPRC2 increases the FSHR accumulation in the early endosomes, and consequently, diminishes its recycling to the cell surface. Hence, in contrast to previously described intra-VHH that disclose active GPCR intracellular location, iPRC2 provokes per se a location bias, through its ability to reroute the FSHR. Thus, it is an innovative tool to examine the functional consequences of GPCR accumulation in various sub-cellular compartments.

pharmacology and toxicology↗

bioRxiv2024

Microstructural Correlates of Cognitive and Motor Functioning Revealed via Multimodal Multivariate Analysis

Recent advances in cognitive neuroscience emphasise the importance of healthy white matter (WM) for optimal behavioural functioning. It is now widely accepted that brain connectivity via WM contributes to the emergence of behaviour. However, the association between the microstructure of WM fibres and behaviour is poorly understood due to the indirect and overlapping nature of methods used to assess microstructure. Here, we used the Mahalanobis Distance (D2) to integrate 10 metrics of WM derived from multimodal neuroimaging that have strong ties to microstructure. The D2 metric was chosen because it accounts for metrics' covariance as it measures the voxelwise distance between every subject and the average; thus providing a robust multiparametric assessment of microstructure. We used multivariate correlation to examine voxelwise WM-behaviour associations with two cognitive and two motor tasks, which allowed us to compare within and across behavioural domains. We observed that behaviour is organised in cognitive, motor, and integrative components that have widespread associations with WM, from frontal to parietal regions. Notably, the decomposition of these factors shows that tasks traditionally labelled as cognitive also contain motor components that map onto motor-related WM patterns, and that motor tasks likewise contain non-motor components linked to distinct WM microstructural features. Our results highlight the complex nature of the links between microstructure and behaviour, and support the relevance of multivariate modelling when examining brain-behaviour associations.

neuroscience↗

bioRxiv2023

A single domain intrabody targeting the follicle-stimulating hormone receptor (FSHR) impacts FSH-induced G protein-dependent signalling

Intracellular variable fragments from heavy-chain antibody from camelids (intra-VHH) have been successfully used as chaperones to solve the 3D structure of active G protein-coupled receptors bound to their transducers. However, their effect on signalling has been poorly explored, although they may provide a better understanding on the relationships between receptor conformation and activity. Here, we isolated and characterized iPRC1, the first intra-VHH recognizing a member of the large glycoprotein hormone receptors family, the follicle-stimulating hormone receptor (FSHR). This intra-VHH recognizes the FSHR 3rd intracellular loop and decreases cAMP production in response to FSH, without altering Gs recruitment. Hence, iPRC1 behaves as an allosteric modulator and provides a new tool to complete structure/activity studies performed so far on this receptor.

pharmacology and toxicology↗

bioRxiv2023

Engineered display of ganglioside-sugars on protein elicits a clonally and structurally constrained B cell response

Ganglioside sugars, as Tumour-Associated Carbohydrate Antigens (TACAs), are long-proposed targets for vaccination and therapeutic antibody production, but their self-like character imparts immunorecessive characteristics that classical vaccination approaches have to date failed to overcome. One prominent TACA, the glycan component of ganglioside GM3 (GM3g), is over-expressed on diverse tumours. To probe the limits of glycan tolerance, we used protein editing methods to display GM3g in systematically varied non-native presentation modes by attachment to carrier protein lysine sidechains using diverse chemical linkers. We report here that such presentation creates glycoconjugates that are strongly immunogenic in mice and elicit robust antigen-specific IgG responses specific to GM3g. Characterisation of this response by antigen-specific B cell cloning and phylogenetic and functional analyses suggests that such display enables the engagement of a highly restricted naive B cell class with a defined germline configuration dominated by members of the IGHV2 subgroup. Strikingly, structural analysis reveals that glycan features appear to be recognised primarily by antibody CDRH1/2, and despite the presence of an antigen-specific Th response and B cell somatic hypermutation, we found no evidence of affinity maturation towards the antigen. Together these findings suggest a reach-through model in which glycans, when displayed in non-self formats of sufficient distance from a conjugate backbone, may engage glycan ready V-region motifs encoded in the germline. Structural constraints define why, despite engaging the trisaccharide, antibodies do not bind natively-presented glycans, such as when linked to lipid GM3. Our findings provide an explanation for the long-standing difficulties in raising antibodies reactive with native TACAs, and provide a possible template for rational vaccine design against this and other TACA antigens. HighlightsO_LIGM3g synthetically coupled via a longer, orthogonal (from backbone) glycoconjugate (LOG) presentation format (thioethyl-lysyl-amidine) display elicits high-titre IgG responses in mice. C_LIO_LIThe germinal centre experience of LOG glycoconjugate-specific B cell responses is directly influenced by the protein backbone. C_LIO_LIStructural characterisation of the antibody response to LOGs reveals highly restricted germline-encoded glycan-engaging motifs that mediate GM3g recognition. C_LIO_LIFailure of antibodies to bind the native trisaccharide highlights barriers to be overcome for the rational design of anti-TACA antibodies. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=172 SRC="FIGDIR/small/543556v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@b2111org.highwire.dtl.DTLVardef@a81b88org.highwire.dtl.DTLVardef@a78c6aorg.highwire.dtl.DTLVardef@1f3b4b9_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2020

Rhamnolipids and their 3-(3-hydroxyalkanoyloxy)alkanoic acid precursors activate Arabidopsis innate immunity through two independent mechanisms

Plant innate immunity is activated upon perception of invasion pattern molecules by plant cell-surface immune receptors. Several bacteria of the genera Pseudomonas and Burkholderia produce rhamnolipids (RLs) from L- rhamnose and (R)-3-hydroxyalkanoate precursors (HAAs). RL and HAA secretion is required to modulate bacterial surface motility, biofilm development, and thus successful colonization of hosts. Here, we show that the lipidic secretome from the opportunistic pathogen Pseudomonas aeruginosa mostly comprising RLs and HAAs stimulates Arabidopsis immunity. We demonstrate that HAAs are sensed by the bulb-type lectin receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION/S-DOMAIN-1-29 (LORE/SD1-29) that also mediates medium-chain 3-hydroxy fatty acid (mc-3-OH-FA) perception in the plant Arabidopsis thaliana. HAA sensing induces canonical immune signaling and local resistance to plant pathogenic Pseudomonas infection. By contrast, RLs trigger an atypical immune response and resistance to Pseudomonas infection independent of LORE. Thus, the glycosyl moieties of RLs, albeit abolishing sensing by LORE, do not impair their ability to trigger plant defense. In addition, our results show that RL-triggered immune response is affected by the sphingolipid composition of the plasma membrane. In conclusion, RLs and their precursors released by bacteria can both be perceived by plants but through distinct mechanisms. SignificanceActivation of plant innate immunity relies on the perception of microorganisms through self and nonself elicitors. Rhamnolipids and their precursor HAAs are exoproducts produced by beneficial and pathogenic bacteria. They are involved in bacterial surface dissemination and biofilm development. As these compounds are released in the extracellular milieu, they have the potential to be perceived by the plant immune system. Our work shows that both compounds independently activate plant immunity. We demonstrate that HAAs are perceived by the receptor protein kinase LORE. By contrast, rhamnolipids are not senses by LORE but activate a non-canonical immune response affected by the sphingolipid composition of the plant plasma membrane. Thus, plants are able to sense bacterial molecules as well as their direct precursors to trigger a distinct immune response.

plant biology↗

bioRxiv2020

Burkholderia thailandensis methylated hydroxy-alkylquinolines: biosynthesis and antimicrobial activity in co-culture experiments

The bacterium Burkholderia thailandensis produces an arsenal of secondary metabolites that have diverse structures and roles in the ecology of this soil-dwelling bacterium. In liquid co-culture experiments, B. thailandensis secretes an antimicrobial that nearly eliminates another soil bacterium, Bacillus subtilis. To identify the antimicrobial, we used a transposon mutagenesis approach. This screen identified antimicrobial-defective mutants with insertions in the hmqA, hmqC and hmqF genes involved in biosynthesis of a family of 2-alkyl-4(1H)-quinolones called 4-hydroxy-3-methyl-2-alkenylquinolines (HMAQs), which are closely related to the Pseudomonas aeruginosa 4-hydroxy-2-alkylquinolines (HAQs). Insertions also occurred in the previously uncharacterized gene BTH_II1576. Results confirm that BTH_II1576 is involved in generating N-oxide derivatives of HMAQs (HMAQ-NO) in B. thailandensis and that HMAQ-NOs are sufficient to eliminate B. subtilis in co-cultures. Moreover, synthetic HMAQ-NO is [~]50-fold more active than HMAQ. Both the methyl group and the length of the carbon side chain account for high activity of HMAQ-NO against B. subtilis. The results provide new information on the biosynthesis and activities of HMAQs and reveal new insight into how these molecules might be important for the ecology of B. thailandensis. IMPORTANCEThe soil bacterium Burkholderia thailandensis produces 2-alkyl-4(1H)-quinolones, mostly methylated 4-hydroxy-alkenylquinolines, a family of relatively unstudied metabolites similar to molecules also synthesized by Pseudomonas aeruginosa. Several of the methylated 4-hydroxy-alkenylquinolines have antimicrobial activity against other species. We show that N-oxidated methyl-alkenylquinolines are particularly antimicrobial and sufficient to kill Bacillus subtilis in co-cultures. We confirmed their biosynthesis requires the previously unstudied protein HmqL. These results provide new information about the biology of 2-alkyl-4(1H)-quinolones, particularly the methylated 4-hydroxy-alkenylquinolines, which are unique to B. thailandensis. This study also has importance for understanding B. thailandensis secondary metabolites and has implications for potential therapeutic development.

microbiology↗

bioRxiv2020

Modulation of bacterial multicellularity via spatiotemporal polysaccharide secretion

AO_SCPLOWBSTRACTC_SCPLOWThe development of multicellularity is a key evolutionary transition allowing for differentiation of physiological functions across a cell population that confers survival benefits; among unicellular bacteria, this can lead to complex developmental behaviours and the formation of higher-order community structures. Herein, we demonstrate that in the social {delta}-proteobacterium Myxococcus xanthus, the secretion of a novel secreted biosurfactant polysaccharide (BPS) is temporally and spatially modulated within communities, mediating swarm migration as well as the formation of multicellular swarm biofilms and fruiting bodies. BPS is a type IV pilus-inhibited acidic polymer built of randomly-acetylated {beta}-linked tetrasaccharide repeats. Both BPS and the "shared good" EPS are produced by dedicated Wzx/Wzy-dependent polysaccharide assembly pathways distinct from that responsible for spore coat assembly. To our knowledge, such pathways have never-before been explicitly shown to synthesize a biosurfactant. Together, these data reveal the central role of secreted polysaccharides in the intricate behaviours coordinating bacterial multicellularity.

microbiology↗