Biology subjects

Guerardel, Y.

Publications and source records attributed to Guerardel, Y..

5 recordsLinked to original sources

bioRxiv2023

Unraveling the Interplay of Temperature Adaptation, Lipidomics, and Environmental Factors in Acinetobacter baumannii Clinical Strains.

Acinetobacter baumannii has gained prominence due to its heightened antibiotic resistance and adaptability within healthcare settings. Unlike other Acinetobacter species, A. baumannii predominantly thrives within healthcare environments, where its persistence is underscored by physiological adaptations, including homeoviscous adaptation that modifies glycerophospholipids (GPL) to enhance membrane flexibility. The bacteriums substantial genetic diversity highlights the paramount importance of prudent strain selection for research involving drug resistance and virulence. This study investigates the lipid composition of six clinical A. baumannii strains, incorporating the highly virulent model strain AB5075 with multiple antibiotic resistances. Our objective is to scrutinize the adaptations of glycerophospholipids (GPL) and glycerolipids (GL) within these isolated strains, each characterized by unique antibiotic resistance profiles, under variable temperature conditions mimicking environmental and physiological scenarios. The strains differential performance in motilities and biofilm formation across varying temperatures reveals intriguing patterns. Notably, the study uncovers a consistent elevation in palmitoleic acid (C16:1) content in five of the six strains at 18{degrees}C. Utilizing LC-HRMS2 analysis, we elucidate shifts in GPL and GL compositions as temperatures oscillate between 18{degrees}C and 37{degrees}C for all strains. Exploration of lipid subspecies further exposes disparities in PE and PG lipids containing C16:1 and oleic acid (C18:1). This investigation not only provides insights into the physiological attributes and survival strategies of A. baumannii but also deepens our comprehension of its adaptive responses to temperature changes. By unraveling the dynamics of lipid composition and fatty acid profiles, this study enriches our understanding of the bacteriums ecological fitness and behavior in diverse environments. IMPORTANCEAcinetobacter baumannii, a bacterium known for its resistance to antibiotics, is a concern in healthcare settings. This study focused on understanding how this bacterium adapts to different temperatures and how its lipid composition changes. Lipids are like the building blocks of its cell membranes. By studying these changes, scientists can gain insights into how the bacterium survives and behaves in various environments. This knowledge helps us better understand its ability to cause infections and resist treatments. The studys findings contribute to our broader understanding of how Acinetobacter baumannii functions, which is important for developing strategies to combat its impact on patient health.

microbiology↗

bioRxiv2023

Bridges instead of boats? The Mla system of diderm Firmicute Veillonella parvula reveals an ancestral transenvelope core of phospholipid trafficking

Despite extensive characterisation of envelope biogenesis systems in diderm bacteria, glycerophospholipid (GPL) trafficking remains poorly understood, and has only been studied in a handful of model species. Within the Proteobacteria, the maintenance of lipid asymmetry (Mla) system facilitates retrograde GPL trafficking via six proteins, MlaA-F. GPLs are extracted from the outer leaflet of the outer membrane by the lipoprotein MlaA which associates with porin trimers, then shipped through the periplasmic space by the chaperone MlaC, which finally delivers GPLs to the inner membrane complex formed by MlaBDEF. Here, we investigate GPL trafficking in Veillonella parvula, a diderm member of the Firmicutes which encodes an Mla system devoid of MlaA and MlaC. V. parvula {Delta}mla mutants display phenotypes characteristic of disrupted lipid asymmetry such as hypervesiculation and detergent hypersensitivity, and lipid content analysis from outer membrane vesicles reveals an enrichment for the major lipid component phosphatidylethanolamine. Interestingly, suppressor analysis identifies mutations in tamB that rescue detergent hypersensitivity and hypervesiculation of {Delta}mla strains, supporting the involvement of these two systems in antagonistic GPL trafficking functions across diverse bacterial lineages. A combination of structural modeling and subcellular localisation assays shows that MlaDVp is longer than in classical diderm models and forms a transenvelope bridge, encoding both an inner membrane-localised MCE domain and an outer membrane {beta}-barrel. These results strongly suggest that V. parvula possesses a minimal Mla system for GPL trafficking, replacing the need for chaperones and outer membrane lipoproteins by directly connecting the two membranes. Finally, phylogenomic analysis indicates that this MlaEFD self-contained architecture is widely distributed in diderm bacteria and most likely represents the ancestral functional core of the Mla system, which subsequently increased in complexity in Proteobacteria and closely related phyla following the emergence of MlaABC. Our work broadens the diversity of current models of GPL trafficking in diderm bacteria, challenging the paradigm set by classical models and shedding light on the evolution of a crucial system in the biogenesis and maintenance of the bacterial outer membrane.

microbiology↗

bioRxiv2022

Structure-Function analysis of Lactiplantibacillus plantarum DltE reveals D-alanylated lipoteichoic acids as direct symbiotic cues supporting Drosophila juvenile growth

Metazoans establish mutually beneficial interactions with their resident microorganisms. However, our understanding of the microbial cues contributing to host physiology remains elusive. Previously, we identified a bacterial machinery encoded by the dlt operon involved in Drosophila melanogasters juvenile growth promotion by Lactiplantibacillus plantarum. Here, using crystallography combined with biochemical and cellular approaches, we investigate the physiological role of an uncharacterized protein (DltE) encoded by this operon. We show that LTAs but not WTAs are D-alanylated in Lactiplantibacillus plantarumNC8 cell envelope and demonstrate that DltE is a D-Ala carboxyesterase removing D-Ala from LTA. Using the mutualistic association of L. plantarumNC8 and Drosophila melanogaster as a symbiosis model, we establish that D-Ala-LTAs are direct symbiotic cues supporting intestinal peptidase expression and juvenile growth in Drosophila. Our results pave the way to probing the contribution of D-Ala-LTA to host physiology in other symbiotic models.

microbiology↗

bioRxiv2022

Structural and functional analysis of natural capsid variants reveals sialic-acid independent entry of BK polyomavirus

BK Polyomavirus (BKPyV) is an opportunistic pathogen that causes nephropathy in kidney transplant recipients. The BKPyV major capsid protein, VP1, engages gangliosides, lipid-linked sialylated glycans at the cell surface, to gain entry into cells. Here, we characterise the influence of VP1 mutations observed in patients with persistent post-transplant BKPyV replication on ganglioside binding, VP1 protein structure, and the tropism of the virus in two renal cell lines: 293TT and immortalised renal tubular epithelial (RS) cells. Infectious entry of single mutants E73Q, E73A and the triple mutant A72V-E73Q-E82Q (VQQ) remained sialic acid-dependent. These three variants acquired binding to a-series gangliosides, including GD1a, although only E73Q was able to infect GD1a-supplemented LNCaP or GM95 cells. Crystal structures of the three mutants showed a clear shift of the BC2 loop in mutants E73A and VQQ that correlated with the inability of these VP1 variants to infect ganglioside complemented cells. On the other hand, the double mutant K69N-E82Q lost the ability to bind sialic acid, with the K69N mutation leading to a steric clash which precludes sialic acid binding. Nevertheless, this mutant retained significant infectivity in 293TT cells that was not dependent on heparan sulphate proteoglycans, implying that an unknown sialic acid-independent entry receptor for BKPyV exists.

microbiology↗

bioRxiv2021

A ganglioside-based senescence-associated immune checkpoint

Senescent cells accumulate in aging tissues, and their elimination can favor healthy aging1-4. Therefore, therapeutic interventions targeting cellular senescence may be promising strategies for delaying or reversing a vast range of age-related diseases5. As cells of the immune system are responsible for senescent cell elimination6-11, a possible anti-aging and pro-healthspan treatment is the specific activation of the immune system to induce senescent cell clearance. However, whether this elimination is limited by an immune checkpoint leading to tolerance of senescence cells is currently unknown. Here, we show that cellular senescence, elicited by various stressors other than oncogenic activation, triggers immune escape toward natural killer (NK) cells, which may thus limit the use of anti-senescence immunotherapies. Moreover, using mass spectrometry, we reveal that senescent cells reshuffle their glycosphingosine composition, toward a marked increase in the ganglioside content, including the appearance of disialylated ganglioside GD3. This senescence associated GD3 overexpression results from transcriptional upregulation of the gene encoding the enzyme ST8SIA1, which is responsible for GD3 synthesis. The high level of GD3 leads to a strong immunosuppressive signal affecting NK cell-mediated immunosurveillance. In a mouse model of lung fibrosis, senescent cell-dependent NK cell immunosuppression is blunted by in vivo administration of anti-GD3 monoclonal antibodies leading to a clear anti-fibrotic effect. These results demonstrate that GD3 upregulation in senescent cells drives a switch from immune clearance toward immune tolerance of senescent cells. Therefore, we propose that GD3 level acts as a senescence-associated immune checkpoint (SIC) that regulates NK cell functions toward senescent cells. Thus, targeting GD3 with specific antibodies may be a promising strategy for the development of effective anti-senescence immunotherapies.

immunology↗