Disruption of TgPHIL1 alters specific parameters of Toxoplasma gondii motility measured in a quantitative, three-dimensional live motility assay.
T. gondii uses substrate-dependent gliding motility to invade cells of its hosts, egress from these cells at the end of its lytic cycle and disseminate through the host organism during infection. The ability of the parasite to move is therefore critical for its virulence. T. gondii engages in three distinct types of gliding motility on coated two-dimensional surfaces: twirling, circular gliding and helical gliding. We show here that motility in a three-dimensional Matrigel-based environment is strikingly different, in that all parasites move in irregular corkscrew-like trajectories. Methods developed for quantitative analysis of motility parameters along the smoothed trajectories demonstrate a complex but periodic pattern of motility with mean and maximum velocities of 0.58 ± 0.07 µm/s and 2.01 ± 0.17 µm/s, respectively. To test how a change in the parasite's crescent shape might affect trajectory parameters, we compared the motility of Δphil1 parasites, which are shorter and wider than wild type, to the corresponding parental and complemented lines. Although comparable percentages of parasites were moving for all three lines, the Δphil1 mutant exhibited significantly decreased trajectory lengths and mean and maximum velocities compared to the parental parasite line. These effects were either partially or fully restored upon complementation of the Δphil1 mutant. These results show that alterations in morphology may have a significant impact on T. gondii motility in an extracellular matrix-like environment, provide a possible explanation for the decreased fitness of Δphil1 parasites in vivo, and demonstrate the utility of the quantitative three-dimensional assay for studying parasite motility.
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America ; Program in Cellular, Molecular and Biomedical Sciences, University of Vermont, Burlington, Vermont, United States of America.
Jacqueline M
JM
Leung
Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, United States of America.
Mark A
MA
Rould
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Christoph
C
Konradt
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Christopher A
CA
Hunter
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
Gary E
GE
Ward
D001681:Biological Assay; D001696:Biomechanical Phenomena; D003094:Collagen / Q000737:chemistry; D003598:Cytoskeletal Proteins / Q000172:deficiency / Q000235:genetics*; D004338:Drug Combinations; D017353:Gene Deletion; D005816:Genetic Complementation Test; D007091:Image Processing, Computer-Assisted; D007797:Laminin / Q000737:chemistry; D008856:Microscopy, Fluorescence; D009068:Movement / Q000502:physiology; D011509:Proteoglycans / Q000737:chemistry; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D014122:Toxoplasma / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence
D003598:Cytoskeletal Proteins; D004338:Drug Combinations; D007797:Laminin; D011509:Proteoglycans; D015800:Protozoan Proteins; C059485:matrigel; D003094:Collagen