DESCRIPTIONS OF MEDICAL FUNGI

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Descriptions of Medical Fungi
Prototheca species are achlorophyllous algae with phylogenetic affinities to the genus
Chlorella. To date only P. wickerhamii and P. zopfii have been involved in human or
animal infections (Lass-Florl and Mayr 2007).
RG-1 organisms.
Prototheca Kruger
Morphological Description: Colonies are smooth, moist, white to cream and yeastlike.
Cultures are sensitive to cycloheximide (actidione) and optimal growth occurs
at 25-30 O C. Mycelium and conidia are absent. Vegetative cells are globose to ovoid,
hyaline, varying in size from approximately 3-30 µm, and have a relatively thick and
highly refractile wall. No budding cells are present; reproduction is by the development
of large sporangia (theca) which contain from 2-20 or more small sporangiospores
(endospores or autospores) which are asexually produced by nuclear division and
cleavage of the cytoplasm.
Molecular Identification: ITS and D1/D2 sequencing is recommended (Wang et al.
2014).
Key Features: Achlorophyllous algae reproducing by sporangia (theca) and
sporangiospores (autospores). Prototheca species which can be differentiated by
assimilation tests and morphological criteria as outlined below. The API 20C yeast
identification strip may be used for species identification.
References: Kaplan (1977), McGinnis (1980), Rippon (1988), Pore (1985), Ueno et al.
(2005), Lass-Florl and Mayr (2007), Wang et al. (2014).
Colony morphology
P. wickerhamii P. zopfii P. stagnora
Hemispheric, with
smooth margin
Flat, rough,
corrugated margin
Flat, with smooth
margin
Cell diameter μm 3-10 7-30 7-14
Growth at 37 O C + + -
Glucose + + +
Trehalose + - -
L-propanol - + +/-
Acetate (pH 5) - + +/-
Galactose + - +
Capsule - - +
5 µm
Prototheca wickerhamii thecae and autospores.