Euglena is a genus of single‐celled, free‐living microorganisms that show both plant‐ and animal‐like characteristics. Members of the genus are found widely in nature and mainly in fresh waters. Most are aerobic and use photosynthesis or many organic compounds as interchangeable sources of carbon and energy. The most studied species is the easily grown E. gracilis which, in spite of its relatively rigid surface, can be subfractionated to yield nuclei, mitochondria, chloroplasts, flagella and pellicles. Subfractions show some unusual characteristics: The nuclear envelope remains intact throughout mitosis and chromosomes are permanently condensed at all phases of the cell cycle, the mitochondrial respiratory chain has two terminal oxidases, and chloroplasts have three membranes reflecting their endosymbiotic evolutionary history. Various Euglena and some of their constituent molecules are useful for environmental biomediation and potentially useful biomedically.

Key Concepts:

  • Euglena is a genus of single‐celled, free living microorganisms that show both plant‐ and animal‐like characteristics.

  • More than 250 Euglena species have been described, though the actual number is not known.

  • The majority of Euglena species are green due to the presence of chloroplasts containing chlorophylls a and b.

  • Members of the genus Euglena are found widely in nature, inhabiting freshwater pools, ponds and lakes.

  • Euglena are able to use photosynthesis and heterotrophic oxidative assimilation as interchangeable and apparently equivalent sources of carbon and energy.

  • How to classify Euglena has been a long‐standing problem; the genus has been claimed as photosynthetic protozoa by zoologists and as algae by botanists.

  • Studies on the genus Euglena, and especially E. gracilis, have been significant for understanding the biochemistry and molecular biology of nuclei and subcellular organisms.

Keywords: single‐celled microorganism; free‐living; taxonomy; nucleus; mitochondrion; chloroplast; bioremediation

Figure 1.

A Euglena cell of the Euglena gracilis type showing the main organelles. From Leedale .



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Further Reading

Ciugulea I and Triemer RE (2010) A Color Atlas of Photosynthetic Euglenoids. East Lansing: Michigan State University Press.

Gojdics M (1953) The Genus Euglena. Madison: The University of Wisconson Press.

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Sleigh M (1989) Protozoa and Other Protists. London: Edward Arnold.

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Buetow, Dennis E(Apr 2011) Euglena. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001964.pub3]