Related Experiment Videos
Phagocytosis by the cellular slime mold Polysphondylium pallidum during growth and development
Abstract:
The phagocytic ability of amoebae of the cellular slime mold Polysphondylium pallidum, grown in shaken suspension, was examined. An established quantitative assay of the uptake of polystyrene (PS) beads was shown to be valid for this organism. The kinetics of phagocytosis were determined, and estimates of the concentration of PS beads necessary to achieve half-maximal phagocytic velocity (K(p)), as well as the maximal velocity itself (V(p) (max)), were made. Comparison with previously published data on Acanthamoeba and guinea pig leukocytes suggested that the P. pallidum amoebae had the lowest K(p), while the leukocytes had the highest V(p) (max). Beads approximately 1 microm in diameter appeared to be the optimal size for ingestion. Simultaneously with phagocytosis, comparable numbers of beads accumulated at the cell surface; this accumulation did not occur when phagocytosis was inhibited. Phagocytosis was depressed by protein in the medium, by increased osmolarity, and by inhibitors of aerobic metabolism. Starvation-initiated development, leading to encystment, was shown to affect the capacity of the cells to phagocytize, mainly by progressively decreasing the time span over which the cells ingested particles at a constant initial rate.
Insights
Polysphondylium pallidum amoebae efficiently phagocytose polystyrene beads, with optimal particle size around 1 micrometer. Phagocytic capacity is influenced by environmental factors and developmental stage.
Area of Science:
- Cell Biology
- Microbiology
- Biochemistry
Background:
- Cellular slime molds, like Polysphondylium pallidum, exhibit phagocytic capabilities crucial for their survival and development.
- Understanding phagocytosis kinetics in these organisms provides insights into cellular uptake mechanisms.
Purpose of the Study:
- To quantify the phagocytic ability of Polysphondylium pallidum amoebae using polystyrene beads.
- To determine the kinetic parameters (K(p) and V(p) (max)) of phagocytosis in P. pallidum.
- To investigate the influence of particle size, environmental conditions, and developmental stage on phagocytosis.
Main Methods:
- Utilized a quantitative assay measuring the uptake of polystyrene (PS) beads by P. pallidum amoebae in shaken suspension.
- Determined phagocytosis kinetics, including half-maximal phagocytic velocity (K(p)) and maximal velocity (V(p) (max)).
- Assessed the effect of bead size, medium composition, osmolarity, metabolic inhibitors, and starvation-induced development on phagocytosis.
Main Results:
- Polysphondylium pallidum amoebae demonstrated efficient phagocytosis of 1-micrometer polystyrene beads, showing the lowest K(p) compared to Acanthamoeba and leukocytes.
- Bead accumulation at the cell surface occurred concurrently with phagocytosis and was dependent on active phagocytic processes.
- Phagocytosis was inhibited by medium protein, increased osmolarity, and aerobic metabolism inhibitors.
- Starvation-induced development progressively reduced the duration of constant-rate particle ingestion.
Conclusions:
- Polysphondylium pallidum exhibits highly efficient phagocytosis with specific kinetic parameters.
- Environmental factors and developmental transitions significantly modulate phagocytic activity in P. pallidum.
- The study validates a quantitative assay for phagocytosis in cellular slime molds and provides comparative data with other phagocytic cells.