Introduction:

Acanthamoeba is a genus of free-living amoebae, one of the most common amoebae found in the soil, water and air. Trophozoites are active forms which require nutrients, undergo replication and are generally motile. Previous studies have reported that Acanthamoeba shows an oriented response to a food source, salmonella typhimurium. An oriented response to a stimulus from external environment is called chemotaxis and observed in both prokaryotes and eukaryotes. Chemotaxis of bacteria is well studies, however, to elucidate the mechanism of chemotaxis needs further study because of its complexity.

Aims:

To study the mechanism of oriented movement of Acanthamoeba; Chemotaxis, Klinokinesis (speed is constant), Orthokinesis (speed changes) or Thigmotaxis (stimulus: touching).

Methods:

A polyphaga locomotion was observed and recorded by digital image capture, using Zeiss microscopes and Improvision., Openlab image analysis software. Time-lapse image sequences were acquired of amoebae in the presence of a directional stimuli, or moving on a lawn of bacteria or fluorescent beads. In addition, matrices images were acquired to elucidate movement of the amoeba population at different time points, rather than individuals in the case of time-lapse of a single field of view.

Results:

The results of this project consist of a variety of image sets. 28 time-lapse sequences, between 30 min and 16 hours duration. Variables include distance of salmonellae from amoebae and time allowed for chemotactic gradient to establish. 20 image matrix sets taken, variables included bacterial/bead density, distance between amoebae and bacteria. These image sets were used for the image analysis by MATLAB in project 2.