Ml. Berbee et Jl. Kerwin, ULTRASTRUCTURAL AND LIGHT-MICROSCOPIC LOCALIZATION OF CARBOHYDRATES AND PEROXIDASE CATALASES IN LAGENIDIUM-GIGANTEUM ZOOSPORES, Mycologia, 85(5), 1993, pp. 734-743
Zoospores of the oomycete Lagenidium giganteum specifically recognize
and then encyst upon mosquito larvae. As a step towards understanding
the basis for this specific recognition, we examined the ultrastructur
e and cytochemistry of the zoospores. Zoospore shape and organellar ar
rangement are similar in L. giganteum and other secondary-type oomycet
e zoospores. The ultrastructure of zoospores of L. giganteum differs f
rom other Oomycetes mainly in details of vesicle morphology and mitoch
ondrial arrangement. In our studies, we emphasized the outer surface o
f the zoospores where recognition molecules are likely to be present.
Using silver methenamine and thiosemicarbazide-silver proteinate stain
sequences, carbohydrate was found at the plasma membrane of zoospores
. Ferritin- and fluorescein-labelled concanavalin A binding patterns i
ndicated alpha-D-mannosyl and/or alpha-D-glucosyl residues are exposed
on the outer surface of the plasma membrane of the zoospore and the w
all of the cyst. Within the zoospores, the membranes of small peripher
al vesicles, and the membranes and contents of golgi apparati and peri
pheral cisternae showed evidence of carbohydrate content with silver s
taining. We did not find clear evidence of carbohydrates among the con
tents of the large and small peripheral vesicles. Zoospores treated wi
th diaminobenzidine to visualize peroxidases and catalases exhibited i
ncreased light and electron opacity in their mitochondria, as well as
a fuzzy coat on the external surfaces of their plasma membranes.