''Prototheca'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

in the family Chlorellaceae. While this genus is a member of the

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

, all ''Prototheca'' no longer have chloroplasts and therefore their

photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...

ability. Some species can cause protothecosis in humans and various

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

Etymology

From the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''proto''- (first) + ''thēkē'' (sheath), ''Prototheca'' is a genus of variably shaped spherical cells of achloric algae in the family Chlorellaceae. Wilhelm Krüger, a German expert in plant physiology and sugar production, reported ''Prototheca'' microorganisms in 1894, shortly after spending 7 years in

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

studying sugarcane. 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 Friedrich (or Friederich) Wilhelm Zopf (12 December 1846 – 24 June 1909) was a well-known German botanist and mycologist. He dedicated to his whole life with fungal biology, particularly in classification of fungi and dye production in fungi an ...

, a renowned botanist, mycologist, and lichenologist.

Biology

''Prototheca'' consists of microscopic, single cells, which may sometimes be clustered to form irregular packets. The cell is generally spherical, ellipsoidal or reniform in shape, with a thin and delicate

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

Chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

s are absent. With the lack of

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

s and

ability, ''Prototheca'' grow heterotrophically and some exhibit

parasitism Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

. Other groups of photosynthetic organisms have undergone similar functional losses in photosynthetic ability and shifted to a parasitic lifestyle, such as in apicomplexans.

Evolution and taxonomy

Although ''Prototheca'' lack chloroplasts, they were recognized early on as closely related to other ''Chlorellaceae'' based on other morphological and physiological traits similar to the group.

Phylogenetics In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

confirm that ''Prototheca'' species are closely related to ''Chlorella'' and other genera, although it is not yet clear whether ''Prototheca'' is a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group.

Pathogenicity

Some species in the genus ''Prototheca'' are known to cause protothecosis, one of the few researched diseases caused by algae, which are categorized as Algaemia. '' P. wickerhamii'' is the main causing agent of protothecosis in humans, and was first identified as such in 1964. A strain of '' P. bovis'' (formerly classified under '' P. zopfii'') is known to cause this disease in cattle, dogs, buffalo, and horses. Symptoms include: Cutaneous lesions, Olecranon bursitis.

References

Trebouxiophyceae genera Chlorellaceae Plants described in 1894 {{green algae-stub