Prototheca [pro″to-the′kə]

Figure 1

Figure 1. Periodic acid‒Schiff‒stained tissue sample from a case-patient who had protothecosis, showing several sphere-like cells of Prototheca spp. Source: Dr. Jerrold Kaplan, Centers for Disease Control, 1971.

Figure 2

Figure 2. Wilhelm Krüger (1857‒1947). Source: Institute for Sugar Beet Research (http://www.ifz-goettingen.de).

From the Greek proto- (first) + thēkē (sheath), Prototheca is a genus of variably shaped spherical cells of achloric algae in the family Chlorellaceae (Figure 1). Wilhelm Krüger, a German expert in plant physiology and sugar production, reported Prototheca microorganisms in 1894, shortly after spending 7 years in Java studying sugarcane (Figure 2). He isolated Prototheca species from the sap of 3 tree species. Krüger named these organisms as P. moriformis and P. zopfii, the second name as a tribute to Friedrich Wilhelm Zopf, a renowned botanist, mycologist, and lichenologist.

Protothecosis affects humans and wild and domestic animals, primarily causing mastitis in cows. Human protothecosis was reported in 1964 from a skin lesion in a farmer from Sierra Leone. There are increasing reports of infections in immunocompromised patients. Debates regarding Prototheca taxonomy persist.