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A conserved pressure-driven mechanism for regulating cytosolic osmolarity.

ABSTRACT: Controlling intracellular osmolarity is essential to all cellular life. Cells that live in hypo-osmotic environments like freshwater must constantly battle water influx to avoid swelling until they burst. Many eukaryotic cells use contractile vacuoles to collect excess water from the cytosol and pump it out of the cell. Although contractile vacuoles are essential to many species, including important pathogens, the mechanisms that control their dynamics remain unclear. To identify basic principles governing contractile vacuole function, we here investigate the molecular mechanisms of two species with distinct vacuolar morphologies from different eukaryotic lineagesâ€"the discoban Naegleria gruberi , and the amoebozoan slime mold Dictyostelium discoideum . Using quantitative cell biology we find that, although these species respond differently to osmotic challenges, they both use actin for osmoregulation, as well as vacuolar-type proton pumps for filling contractile vacuoles. We also use analytical modeling to show that cytoplasmic pressure is sufficient to drive water out of contractile vacuoles in these species, similar to findings from the alveolate Paramecium multimicronucleatum . Because these three lineages diverged well over a billion years ago, we propose that this represents an ancient eukaryotic mechanism of osmoregulation.

SUBMITTER: Velle KB

PROVIDER: S-EPMC10002747 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature

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A conserved pressure-driven mechanism for regulating cytosolic osmolarity.

Velle Katrina B KB Garner Rikki M RM Beckford Tatihana K TK Weeda Makaela M Liu Chunzi C Kennard Andrew S AS Edwards Marc M Fritz-Laylin Lillian K LK

bioRxiv : the preprint server for biology 20230302

Controlling intracellular osmolarity is essential to all cellular life. Cells that live in hypo-osmotic environments like freshwater must constantly battle water influx to avoid swelling until they burst. Many eukaryotic cells use contractile vacuoles to collect excess water from the cytosol and pump it out of the cell. Although contractile vacuoles are essential to many species, including important pathogens, the mechanisms that control their dynamics remain unclear. To identify basic principle ...[more]

PMID: 36909496

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Project description:Perturbation of natural microbial communities by antimicrobials, such as triclosan, can result in selection for antibiotic tolerance, which is of particular concern when pathogens are present. Members of the genus Pseudomonas are found in many natural microbial communities and frequently demonstrate increased abundance following triclosan exposure. The pathogen and well-studied model organism Pseudomonas aeruginosa exhibits high triclosan tolerance; however, it is unknown if all Pseudomonas species share this trait or if there are susceptible strains. We characterized the triclosan tolerance phenotypes of diverse Pseudomonas isolates obtained from triclosan-exposed built environments and identified both tolerant and sensitive strains. High tolerance is associated with carriage of the enoyl-acyl carrier reductase (ENR) isozyme gene fabV, compared to the lesser protective effects of efflux or presence of ENRs. Given its unique importance, we examined fabV distribution throughout Pseudomonas species using large-scale phylogenomic analyses. We find fabV presence or absence is largely invariant at the species level but demonstrates multiple gain and loss events in its evolutionary history. We further provide evidence of its presence on mobile genetic elements. Our results demonstrate the surprising variability in triclosan tolerance in Pseudomonas and confirm fabV to be a useful indicator for high triclosan tolerance in Pseudomonas These findings provide a framework for better monitoring of Pseudomonas in triclosan-exposed environments and interpreting effects on species and gene composition.IMPORTANCE Closely related species are typically assumed to demonstrate similar phenotypes driven by underlying conserved genotypes. When monitoring for the effect of antimicrobials on the types of species that may be selected for, this assumption may prove to be incorrect, and identification of additional genetic markers may be necessary. We isolated several phylogenetically diverse members of Pseudomonas from indoor environments and tested their phenotypic tolerance toward the commonly used antimicrobial triclosan. Although Pseudomonas isolates are broadly regarded to be highly triclosan tolerant, we demonstrate the presence of both triclosan-tolerant and -susceptible strains, separated by a difference in tolerance of nearly 3 orders of magnitude. Bioinformatic and experimental investigation demonstrated that the presence of the gene fabV was associated with high tolerance. We demonstrate that fabV is not evenly distributed in all Pseudomonas species and that its presence could be a useful predictor of high triclosan tolerance suitable for antimicrobial monitoring efforts involving triclosan.

Dataset Information

A conserved pressure-driven mechanism for regulating cytosolic osmolarity.

Publications

A conserved pressure-driven mechanism for regulating cytosolic osmolarity.

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