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Natural Product Research Jun 2024The rise of antibiotic-resistant bacterial strains represents an important challenge for global health, underscoring the critical need for innovative strategies to...
The rise of antibiotic-resistant bacterial strains represents an important challenge for global health, underscoring the critical need for innovative strategies to confront this threat. Natural products and their derivatives have emerged as a promising reservoir for drug discovery. The social amoeba is a potent model organism in this effort. Employing this invertebrate model, we introduce a novel perspective to investigate natural plant extracts in search of molecules with potential antivirulence activity. Our work established an easy-scalable developmental assay targeting a virulent strain of , with as the representative plant. The main objective was to identify tentative compounds from the extract that attenuate the virulence of virulence without inducing cytotoxic effects on amoeba cells. Notably, the methanolic root extract of fulfilled these prerequisites compared to the dichloromethane extract. Using UHPLC Q/Orbitrap/ESI/MS/MS, 63 compounds were tentatively identified in both extracts, 47 in the methanolic and 29 in the dichloromethane, with 13 compounds in common. This research underscores the potential of employing -assisted pharmacognosy to discover new antivirulence agents against multidrug-resistant pathogens.
PubMed: 38829280
DOI: 10.1080/14786419.2024.2360166 -
BioRxiv : the Preprint Server For... Oct 2023The actin cortex is very dynamic during migration of eukaryotes. In cells that use blebs as leading-edge protrusions, the cortex reforms beneath the cell membrane (bleb...
The actin cortex is very dynamic during migration of eukaryotes. In cells that use blebs as leading-edge protrusions, the cortex reforms beneath the cell membrane (bleb cortex) and completely disassembles at the site of bleb initiation. Remnants of the actin cortex at the site of bleb nucleation are referred to as the actin scar. We refer to the combined process of cortex reformation along with the degradation of the actin scar during bleb-based cell migration as . The molecular factors that regulate the dynamic reorganization of the cortex are not fully understood. Myosin motor protein activity has been shown to be necessary for blebbing, with its major role associated with pressure generation to drive bleb expansion. Here, we examine the role of myosin in regulating cortex dynamics during bleb stabilization. Analysis of microscopy data from protein localization experiments in cells reveals a rapid formation of the bleb's cortex with a delay in myosin accumulation. In the degrading actin scar, myosin is observed to accumulate before active degradation of the cortex begins. Through a combination of mathematical modeling and data fitting, we identify that myosin helps regulate the equilibrium concentration of actin in the bleb cortex during its reformation by increasing its dissasembly rate. Our modeling and analysis also suggests that cortex degradation is driven primarily by an exponential decrease in actin assembly rate rather than increased myosin activity. We attribute the decrease in actin assembly to the separation of the cell membrane from the cortex after bleb nucleation.
PubMed: 37961169
DOI: 10.1101/2023.10.26.564082 -
Evolution Letters Jun 2024In facultative symbioses, only a fraction of hosts are associated with symbionts. Specific host and symbiont pairings may be the result of host-symbiont coevolution...
In facultative symbioses, only a fraction of hosts are associated with symbionts. Specific host and symbiont pairings may be the result of host-symbiont coevolution driven by reciprocal selection or priority effects pertaining to which potential symbiont is associated with a host first. Distinguishing between these possibilities is important for understanding the evolutionary forces that affect facultative symbioses. We used the social amoeba, , and its symbiont, , to determine whether ongoing coevolution affects which host-symbiont strain pairs naturally cooccur within a facultative symbiosis. Relative to other , including another symbiont of , features a reduced genome size that indicates a significant history of coevolution with its host. We hypothesized that ongoing host-symbiont coevolution would lead to higher fitness for naturally cooccurring (native) host and symbiont pairings compared to novel pairings. We show for the first time that symbionts can horizontally transmit to new amoeba hosts when hosts aggregate together during the social stage of their life cycle. Here we find evidence for a virulence-transmission trade-off without host specificity. Although symbiont strains were significantly variable in virulence and horizontal transmission rate, hosts and symbionts responded similarly to associations in native and novel pairings. We go on to identify candidate virulence factors in the genomes of strains that may contribute to variation in virulence. We conclude that ongoing coevolution is unlikely for and The system instead appears to represent a stable facultative symbiosis in which naturally cooccurring host and symbiont pairings are the result of priority effects.
PubMed: 38818420
DOI: 10.1093/evlett/qrae001 -
International Journal of Molecular... Dec 2023In this work, we established, validated, and optimized a novel computational framework for tracing arbitrarily oriented actin filaments in cryo-electron tomography maps....
In this work, we established, validated, and optimized a novel computational framework for tracing arbitrarily oriented actin filaments in cryo-electron tomography maps. Our approach was designed for highly complex intracellular architectures in which a long-range cytoskeleton network extends throughout the cell bodies and protrusions. The irregular organization of the actin network, as well as cryo-electron-tomography-specific noise, missing wedge artifacts, and map dimensions call for a specialized implementation that is both robust and efficient. Our proposed solution, , accumulates densities along paths of a specific length in various directions, starting from locally determined seed points. The highest-density paths originating from the seed points form short linear candidate filament segments, which are further scrutinized and classified by users via inspection of a novel , which visualizes the likelihood of being a part of longer filaments. The pruned linear candidate filament segments are then iteratively fused into continuous, longer, and curved filaments based on their relative orientations, gap spacings, and extendibility. When applied to the simulated phantom tomograms of a filopodium under experimental conditions, demonstrated high efficacy, with F1-scores ranging from 0.85 to 0.90, depending on the noise level. Furthermore, when applied to a previously untraced experimental tomogram of mouse fibroblast lamellipodia, the filaments predicted by exhibited a good visual agreement with the experimental map. The framework is highly time efficient and can complete the tracing process in just a few minutes. The source code is publicly available with version 3.2 of the free and open-source software package.
Topics: Mice; Animals; Dictyostelium; Actin Cytoskeleton; Cytoskeleton; Actins; Electron Microscope Tomography
PubMed: 38139012
DOI: 10.3390/ijms242417183 -
PeerJ 2024The evolution of symbiotic interactions may be affected by unpredictable conditions. However, a link between prevalence of these conditions and symbiosis has not been...
The evolution of symbiotic interactions may be affected by unpredictable conditions. However, a link between prevalence of these conditions and symbiosis has not been widely demonstrated. We test for these associations using social amoebae and their bacterial endosymbionts. commonly hosts endosymbiotic bacteria from three taxa: and Chlamydiae. Three species of facultative endosymbionts are the best studied and give hosts the ability to carry prey bacteria through the dispersal stage to new environments. and Chlamydiae are obligate endosymbiont lineages with no measurable impact on host fitness. We tested whether the frequency of both single infections and coinfections of these symbionts were associated with the unpredictability of their soil environments by using symbiont presence-absence data from isolates from 21 locations across the eastern United States. We found that symbiosis across all infection types, symbiosis with and Chlamydiae obligate endosymbionts, and symbiosis involving coinfections were not associated with any of our measures. However, unpredictable precipitation was associated with symbiosis in two species of , suggesting a link between unpredictable conditions and symbiosis.
Topics: Symbiosis; Soil Microbiology; Dictyostelium; Burkholderiaceae; Soil; United States; Chlamydia
PubMed: 38784393
DOI: 10.7717/peerj.17445 -
The ISME Journal Dec 2023The soil amoeba Dictyostelium discoideum acts as both a predator and potential host for diverse bacteria. We tested fifteen Pseudomonas strains that were isolated from...
The soil amoeba Dictyostelium discoideum acts as both a predator and potential host for diverse bacteria. We tested fifteen Pseudomonas strains that were isolated from transiently infected wild D. discoideum for ability to escape predation and infect D. discoideum fruiting bodies. Three predation-resistant strains frequently caused extracellular infections of fruiting bodies but were not found within spores. Furthermore, infection by one of these species induces secondary infections and suppresses predation of otherwise edible bacteria. Another strain can persist inside of amoebae after being phagocytosed but is rarely taken up. We sequenced isolate genomes and discovered that predation-resistant isolates are not monophyletic. Many Pseudomonas isolates encode secretion systems and toxins known to improve resistance to phagocytosis in other species, as well as diverse secondary metabolite biosynthetic gene clusters that may contribute to predation resistance. However, the distribution of these genes alone cannot explain why some strains are edible and others are not. Each lineage may employ a unique mechanism for resistance.
Topics: Animals; Predatory Behavior; Dictyostelium; Pseudomonas; Amoeba; Bacteria
PubMed: 37884792
DOI: 10.1038/s41396-023-01535-5 -
Biophysical Journal Nov 2023Here, we investigate how a subpopulation of cells can move through an aggregate of cells. Using a stochastic force-based model of Dictyostelium discoideum when the...
Here, we investigate how a subpopulation of cells can move through an aggregate of cells. Using a stochastic force-based model of Dictyostelium discoideum when the population is forming a slug, we simulate different strategies for prestalk cells to reliably move to the front of the slug while omitting interaction with the substrate thus ignoring the overall motion of the slug. Of the mechanisms that we simulated, prestalk cells being more directed is the best strategy followed by increased asymmetric motive forces for prestalk cells. The lifetime of the cell adhesion molecules, while not enough to produce differential motion, did modulate the results of the strategies employed. Finally, understanding and simulating the appropriate boundary conditions are essential to correctly predict the motion.
Topics: Dictyostelium; Cell Movement; Models, Biological
PubMed: 37752701
DOI: 10.1016/j.bpj.2023.09.013 -
Biophysical Journal May 2024Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) is a signaling lipid on the plasma membrane that plays a fundamental role in cell signaling with a strong impact on...
Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) is a signaling lipid on the plasma membrane that plays a fundamental role in cell signaling with a strong impact on cell physiology and diseases. It is responsible for the protruding edge formation, cell polarization, macropinocytosis, and other membrane remodeling dynamics in cells. It has been shown that the membrane confinement and curvature affects the wave formation of PIP3 and F-actin. But, even in the absence of F-actin, a complex self-organization of the spatiotemporal PIP3 waves is observed. In recent findings, we have shown that these waves can be guided and pinned on strongly bended Dictyostelium membranes caused by molecular crowding and curvature-limited diffusion. Based on these experimental findings, we investigate the spatiotemporal PIP3 wave dynamics on realistic three-dimensional cell-like membranes to explore the effect of curvature-limited diffusion, as observed experimentally. We use an established stochastic reaction-diffusion model with enzymatic Michaelis-Menten-type reactions that mimics the dynamics of Dictyostelium cells. As these cells mimic the three-dimensional shape and size observed experimentally, we found that the PIP3 wave directionality can be explained by a Hopf-like and a reverse periodic-doubling bifurcation for uniform diffusion and curvature-limited diffusion properties. Finally, we compare the results with recent experimental findings and discuss the discrepancy between the biological and numerical results.
Topics: Cell Membrane; Dictyostelium; Phosphatidylinositol Phosphates; Models, Biological; Diffusion
PubMed: 38515298
DOI: 10.1016/j.bpj.2024.03.022 -
Cell Adhesion & Migration Dec 2024Copines are a family of calcium-dependent membrane-binding proteins. To study these proteins, anull mutant for was created in , which has six copines genes (). During...
Copines are a family of calcium-dependent membrane-binding proteins. To study these proteins, anull mutant for was created in , which has six copines genes (). During development, cells were able to aggregate, but did not form streams. Once aggregated into mounds, they formed large ring structures. cells were less adherent to plastic substrates, but more adherent to other cells. These phenotypes correlated with changes in adhesion protein expression with decreased expression of SibA and increased expression of CsaA in developing cells. We also measured the expression of RegA, a cAMP phosphodiesterase, and found that cells have reduced RegA expression. The reduced RegA expression in cells is most likely responsible for the observed phenotypes.
Topics: Dictyostelium; Carrier Proteins
PubMed: 38378453
DOI: 10.1080/19336918.2024.2315629 -
Cells Mar 2024Autosomal dominant polycystic kidney disease (ADPKD) occurs when the proteins Polycystin-1 (PC1, ) and Polycystin-2 (PC2, ) contain mutations. PC1 is a large membrane...
Autosomal dominant polycystic kidney disease (ADPKD) occurs when the proteins Polycystin-1 (PC1, ) and Polycystin-2 (PC2, ) contain mutations. PC1 is a large membrane receptor that can interact and form a complex with the calcium-permeable cation channel PC2. This complex localizes to the plasma membrane, primary cilia and ER. Dysregulated calcium signalling and consequential alterations in downstream signalling pathways in ADPKD are linked to cyst formation and expansion; however, it is not completely understood how PC1 and PC2 regulate calcium signalling. We have studied Polycystin-2 mediated calcium signalling in the model organism by overexpressing and knocking down the expression of the endogenous Polycystin-2 homologue, Polycystin-2. Chemoattractant-stimulated cytosolic calcium response magnitudes increased and decreased in overexpression and knockdown strains, respectively, and analysis of the response kinetics indicates that Polycystin-2 is a significant contributor to the control of Ca responses. Furthermore, basal cytosolic calcium levels were reduced in Polycystin-2 knockdown transformants. These alterations in Ca signalling also impacted other downstream Ca-sensitive processes including growth rates, endocytosis, stalk cell differentiation and spore viability, indicating that is a useful model to study Polycystin-2 mediated calcium signalling.
Topics: Humans; Polycystic Kidney, Autosomal Dominant; Dictyostelium; TRPP Cation Channels; Calcium; Calcium Signaling; Calcium Channels
PubMed: 38607049
DOI: 10.3390/cells13070610