Biology subjects

Acket, S.

Publications and source records attributed to Acket, S..

3 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↗

bioRxiv2021

Extreme longevity of highly fecund termite queens achieved by mitochondrial and insulin upregulation without harmful lipid signatures or accumulation

Kings and queens of eusocial termites can live for decades, while queens sustain a nearly maximal fertility. To investigate the molecular mechanisms underlying their long lifespan, we carried out transcriptomics, lipidomics and metabolomics in Macrotermes natalensis on sterile short-lived workers, long-lived kings and five stages spanning twenty years of adult queen maturation. Reproductives share gene expression differences from workers in agreement with a reduction of several aging-related processes, involving upregulation of DNA damage repair and mitochondrial functions. Anti-oxidant gene expression is downregulated, while peroxidability of membranes in queens decreases. Against expectations, we observed an upregulated gene expression in fat bodies of reproductives of several components of the IIS pathway, including an insulin-like peptide, Ilp9. This pattern does not lead to deleterious fat storage in physogastric queens, while simple sugars dominate in their hemolymph and large amounts of resources are allocated towards oogenesis. Our findings support the notion that all processes causing aging need to be addressed simultaneously in order to prevent it.

molecular biology↗

bioRxiv2020

The impact of plasma membrane lipid composition on flagella-mediated adhesion of enterohemorrhagic Escherichia coli

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a major cause of foodborne gastrointestinal illness. The adhesion of EHEC on host tissues is the first step enabling bacterial colonization. Adhesins like fimbriae and flagella mediate this mechanism. Here, we studied the interaction of the bacterial flagellum with the host cell’s plasma membrane using Giant Unilamellar Vesicles (GUVs) as a biologically relevant model. Cultured cell lines contain many different molecular components including proteins and glycoproteins. In contrast, with GUVs we can characterize the bacterial mode of interaction solely with a defined lipid part of the cell membrane. Bacterial adhesion on GUVs was dependent on the presence of the flagellar filament and its motility. By testing different phospholipid head groups, the nature of the fatty acid chains or the liposome curvature, we found that lipid packing is a key parameter to enable bacterial adhesion. Using HT-29 cells grown in the presence of polyunsaturated fatty acid (α-linolenic acid) or saturated fatty acid (palmitic acid), we found that α-linolenic acid reduced adhesion of wild type EHEC but not of a non-flagellated mutant. Finally, our results reveal that the presence of flagella is advantageous for the bacteria to bind to lipid rafts. We speculate that polyunsaturated fatty acids prevent flagellar adhesion on membrane bilayers and play a clear role for optimal host colonization. Flagella-mediated adhesion to plasma membranes has broad implications to host-pathogen interactions.Importance Bacterial adhesion is a crucial step to allow bacteria to colonize their hosts, invade tissues and form biofilm. Enterohemorrhagic E. coli O157:H7 is a human pathogen and the causative agent of diarrhea and hemorrhagic colitis. Here, we use biomimetic membrane models and cell lines to decipher the impact of lipid content of the plasma membrane on enterohemorrhagic E. coli flagella-mediated adhesion. Our findings provide evidence that polyunsaturated fatty acid (α-linolenic acid) inhibits E. coli flagella adhesion to the plasma membrane in a mechanism separate from its antimicrobial and anti-inflammatory functions. In addition, we confirm that cholesterol-enriched lipid microdomains, often called lipid rafts are important in bacterial adhesion. These findings significantly strengthen plasma membrane adhesion via bacterial flagella in an important human pathogen. This mechanism represents a promising target for the development of novel anti-adhesion therapies.Competing Interest StatementThe authors have declared no competing interest.View Full Text

microbiology↗