The ultrastructural morphology of Eimeria tenella exhibits striking natural variation and undergoes significant changes during the first few hours of infection
The data generated during this PhD provides novel insights into the biology of Eimeria parasites:
protozoan organisms capable of causing enteric disease in a vast array of animals. Working with
Eimeria tenella, a clinically and economically significant pathogen of chickens, I have quantified the
fusion dynamics of the refractile bodies. Refractile bodies are non-membrane-bound organelles with
immunogenic properties and unknown function. The structural and temporal dynamics of refractile
body merger shares striking similarity with that of intrinsically disordered protein-containing droplet
organelles; this comparison may help to direct future research into the character and function of these
mysterious organelles. In an adjacent project, the organelle numbers and volumes for the E. tenella
sporozoite stage were quantified. The resultant data shows a surprisingly high level of variability in
cell morphometry; this could be due to genetic/epigenetic factors or may reflect an undiscovered
maturation phase. The conoid is a cytoskeletal structure found in many important apicomplexan
pathogens and is involved in host cell invasion and parasite motility. I have performed the first high
resolution quantitative investigation of three-dimensional conoid structure and show that there is also
a considerable level variability in conoid structure. Conoid fibre number was found to vary from 13
to 16 per conoid. This variation was seen in both freshly hatched and post-invasion sporozoites,
suggesting that genetic factors are involved. Following analysis of structures within the conoid, my
data suggests that secretory organelle protein release occurs through intra-conoidal transport,
docking and fusion