Biology subjects

Rossi, C.

Publications and source records attributed to Rossi, C..

23 records · Page 2Linked to original sources

bioRxiv2020

Two-dimensional video-based analysis of human gait using pose estimation

Walking is the primary mode of human locomotion. Accordingly, people have been interested in studying human gait since at least the fourth century BC. Human gait analysis is now common in many fields of clinical and basic research, but gold standard approaches - e.g., three-dimensional motion capture, instrumented mats or footwear, and wearables - are often expensive, immobile, data-limited, and/or require specialized equipment or expertise for operation. Recent advances in video-based pose estimation have suggested exciting potential for analyzing human gait using only two-dimensional video inputs collected from readily accessible devices (e.g., smartphones, tablets). However, we currently lack: 1) data about the accuracy of video-based pose estimation approaches for human gait analysis relative to gold standard measurement techniques and 2) an available workflow for performing human gait analysis via video-based pose estimation. In this study, we compared a large set of spatiotemporal and sagittal kinematic gait parameters as measured by OpenPose (a freely available algorithm for video-based human pose estimation) and three-dimensional motion capture from trials where healthy adults walked overground. We found that OpenPose performed well in estimating many gait parameters (e.g., step time, step length, sagittal hip and knee angles) while some (e.g., double support time, sagittal ankle angles) were less accurate. We observed that mean values for individual participants - as are often of primary interest in clinical settings - were more accurate than individual step-by-step measurements. We also provide a workflow for users to perform their own gait analyses and offer suggestions and considerations for future approaches.

bioengineering↗

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↗

bioRxiv2019

Flagella methylation promotes bacterial adhesion and host cell invasion

The flagellum is the motility device of many bacteria and the long external filament is made of several thousand copies of a single protein, flagellin. While posttranslational modifications of flagellin are common among bacterial pathogens, the role of lysine methylation remained unknown. Here, we show that both flagellins of Salmonella enterica, FliC and FljB, are methylated at surface-exposed lysine residues. A Salmonella mutant deficient in flagellin methylation was outcompeted for gut colonization in a gastroenteritis mouse model. In support, methylation of flagellin promoted invasion of epithelial cells in vitro. Lysine methylation increased the surface hydrophobicity of flagellin and enhanced flagella-dependent adhesion of Salmonella to phosphatidylcholine vesicles and epithelial cells. In summary, posttranslational flagellin methylation constitutes a novel mechanism how flagellated bacteria facilitate adhesion to hydrophobic host cell surfaces and thereby contributes to efficient gut colonization and successful infection of the host.

microbiology↗

bioRxiv2019

Nuclear lipidome is altered in amyotrophic lateral sclerosis: a preliminary study

In this pilot study, we show that nuclei in spinal cord from ALS patients exhibit a differential lipidomic signature. Among the differential lipid species we could annotate 41 potential identities. These comprise membrane-bound lipids such as phosphatidylethanolamines-including plasmalogens- and phosphatidylcholines but also other lipid classes such as glycosphingolipids, diacylglycerols, and triacylglycerides (potentially present as nuclear lipid droplets). These results were orthogonally validated by showing loss of alkyldihydroxyacetonephosphate synthase (AGPS), a key peroxisomal enzyme in plasmalogen synthesis, both in ALS necropsy samples, in human motor neurons derived from iPSC from ALS patients and in hSOD-G93A transgenic mice. Further, diacylglycerol content changes were associated to ALS-linked variations in related-enzymes, such as phospholipase C {beta}I (PLC{beta}I), the source of nuclear diacylglycerol, and protein kinase C{beta}II (PKC{beta}II), whose function partially depends on nuclei concentration of diacylglycerol. These results point out for not only a role of nuclear membrane lipids but also to lipids present in the nucleoplasm, suggesting an undisclosed role for this part of the subcellular lipidome in ALS pathophysiology.

neuroscience↗

bioRxiv2018

Description and charactrization of the Amazonian entomopathogenic bacterium Photorhabdus luminescens MN7

Many isolates of the genus Photorhabdus have been reported around the world. Here we describe the first Brazilian Photorhabdus isolate, found in association with the entomopathogenic nematode Heterorhabditis baujardi LPP7, from the Amazonian forest in Monte Negro (RO, Brazil). The new isolate can be grouped with the Hb-Hm clade of P. luminescens subsp. luminescens, close to the new subspecies P. luminescens subsp. sonorensis. P. luminescens MN7 has several characteristics expected of variant form I cells, such as the presence of intracellular crystals, secretion of hydrolytic enzymes (lipases and proteases) and bioluminescence. Although H. baujardi LPP7 is not prolific when compared to H. bacteriophora HP88, P. luminescens MN7 is clearly pathogenic and probably secretes the same toxins as P. luminescens subsp. luminescens W14, when fed to larvae of the greater wax moth Galleria mellonella. This behavior is different from what is found in Photorhabdus luminescens subsp. laumondii HP88, which was used as a control in our experiments, and P. l. subsp. laumondii TT01. Besides the toxin secretion, P. luminescens MN7 secretes proteolytic polypeptides that have molecular masses different from those found in P. l. subsp. laumondii TT01. Finally, the crude extract from spent culture medium was shown to contain 3,5-dihydroxy-4-isopropyl-cis-stilbene and 1,3,8-trihydroxy-9,10-anthraquinone as the major compounds, similarly to other Photorhabdus luminescens strains.

microbiology↗