Comparative studies on related free-living and pathogenic limax amoebae with particular reference to Naegleria.
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Date
1977
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Abstract
Over two hundred and forty strains of limax amoeba including eight potentially pathogenic strains of Naegleria and Acanthamoeba were isolated
from a variety of habitats in South Africa.
The amoeboid and flagellate stages of all Naegleria strains examined
by light microscopy were found to be similar in morphology. Differences
were noted in the excystment of Naegleria fowleri, Naegleria gruberi and
other limax amoebae.
Time-lapse microcinematography has been utilised to study cytokinesis
and motility in the amoeboid and flagellate stages of Naegleria fowleri
and Naegleria gruberi. A new phenomenon was observed in Naegleria where
amoebae attempted cytokinesis after brief exposure to a temperature
of 9°C.
The amoeboid and flagellate stages of virulent and avirulent Naegleria
were found to be similar in surface topology when examined under the scanning
electron microscope. Differences were noted in the excystment patterns
of various limax amoebae. No structure suggestive of a surface active
lysosome was found in any of the cells examined.
A comparative transmission electron microscope study of virulent
and avirulent Naegleria and other limax amoebae has revealed striking
similarities as well as sharply defined ultrastructural differences.
Partioles suggestive of a virus were detected in several of the pathogenic
Naegleria. Surface-active lysosomes were not found in any of the amoebae
examined.
Distinct feeding preferences were evident in Naegleria fowleri and
Naegleria gruberi when they were tested on a variety of gram-negative and
gram-positive bacteria. Differences were noted on the growth of these
amoebae at various temperatures. Cell fractions of Pseudomonas aeruginosa
affected excystment, encystment, cell division and the amoeba-to-flagellate
transformation in Naegleria.
Differences were observed in the transformation kinetics of Naegleria
fowleri and Naegleria gruberi at 25ºC and 43º C. A variety of inhibitors
affected motility and transformation in Naegleria. For the first time,
La[3+]ion, a competitive inhibitor of Ca[2+]ion, was shown to inhibit amoeboid
motion, transformation and flagellar beating in Naegleria. Electron
microscope observation suggested that La[3+]ion acts on the plasmalemma.
Material from two suspected cases of primary amoebic meningoencephalitis
was examined and cultured but no limax amoebae were isolated.
New criteria for the classification of virulent and avirulent Naeglerid.
have been advanced.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1977.
Keywords
Amoeba., Theses--Zoology.