Protozoa

11 Key excerpts on "Protozoa"

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  eBook - ePub

  Thorp and Covich's Freshwater Invertebrates

  Ecology and General Biology

  • James H. Thorp, D. Christopher Rogers(Authors)
  • 2014(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 7

  Free-Living Protozoa

  Genoveva F. Esteban     Centre for Conservation Ecology and Environmental Science, Faculty of Science and Technology, Bournemouth University, Poole, Dorset, UK

  Bland J. Finlay     The River Laboratory, Queen Mary University of London, Wareham, Dorset, UK

  Alan Warren     Department of Life Sciences, Natural History Museum, London, UK

  Abstract

  Protozoa are microscopic, single-celled eukaryotic organisms. Each protozoon typically exists as an independent cell, and all free-living Protozoa are defined as phagotropic microorganisms. In some species, the cells unite to form colonies. Many Protozoa can cause disease (e.g., malaria), others are commensals in the digestive tracts of ruminants and wood-eating insects. In this chapter we will focus on the free-living Protozoa. The definition of this group is not taxonomic but one that is based on its key function in the natural environment. Protozoa are capable of phagotrophy, i.e. the ability to capture and ingest food particles. Many Protozoa are “mixotrophs” and capable of both phagotrophy and phototrophy (photosynthesis), the latter via functional chloroplasts or endosymbiotic algae. Like most microorganisms, Protozoa have very large population sizes, and they are the most abundant group of phagotrophs in the biosphere. Biodiversity at the level of Protozoa has characteristics that are not shared by macroscopic animals and plants. Most Protozoan species are probably globally ubiquitous. As a consequence, a significant proportion of local Protozoan species richness at any moment in time, is rare or cryptic and awaiting the arrival of conditions suitable for growth and reproduction.

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  Microbial Pathogens and Human Diseases

  • N A Khan(Author)
  • 2008(Publication Date)
  • CRC Press

    (Publisher)

  CHAPTER 5 Protozoa 1. INTRODUCTION The term Protozoa is derived from 'proto' meaning 'first' and 'zoa' meaning 'animal'. Protozoa are 'first animals' which generally describes their animal­ like nutrition. Protozoa are the largest group of single-celled, microscopic organisms with more than 20,000 species that are found in all aspects of life. Protozoa are widely distributed in various environments from favourable rainforests to sandy beaches to the bottom of oceans to snow- covered mountains. With the availability of improved diagnostic methods, Protozoa are being discovered from diverse habitats. However, the abundance and diversity of Protozoa in ecosystems is dependent on abiotic factors such as water, temperature, pH, salinity, osmolarity and biotic factors including the availability of food particles. Protozoa include the causative agents of some of the most notorious and deadly diseases. For example, malaria alone causes between one to two million deaths worldwide, annually. Other Protozoa play important roles in the food chain maintaining a balanced ecosystem or act as commensal organisms (not harmful) of nearly all humans. Some of the Protozoan pathogens have only recently been identified as a major threat to human health. For example, Cryptosporidium was originally described in the 19th century, but has recently been associated with serious human infections in AIDS patients. With the increasing number of AIDS patients during the last few decades, many of the Protozoan pathogens have become a major problem to human health. 2. Protozoa: CELLULAR PROPERTIES Protozoa are the largest single-cell non-photosynthetic animals, which lack cell walls. The study of Protozoa, invisible to the naked eye, was initiated 183 with the discovery of the microscope in 1600s by Antonio van Leeuwenhoek (1632 -1723). The majority of Protozoan pathogens are less than 150 pm in size with the smallest one between 1 -1 0 pm.

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  Maintaining Cultures for Biotechnology and Industry

  • Jennie C. Hunter-Cevera, Angela Belt(Authors)
  • 1996(Publication Date)
  • Academic Press

    (Publisher)

  C HAPTER 7 Protozoa Ellen M. Simon Thomas A. Nerad Background Introduction Protozoa have been defined as one-celled or colonial (polycellular) organism[s] possessing all of the elegantly coordinated processes of life, usually (though not exclusively) animal like within the boundaries of a single cell (Anderson, 1988). The Protozoa are significant components of the biota of diverse ecosystems; they exist in soils from polar regions to hot spring runoffs, in marine, estuary, or fresh water, at all altitudes, in sewage treatment systems, and in droplets trapped in flowers and banana plants. Their associations with other organisms include symbiosis, commen- salism, and parasitism--for example, the obligate parasitism of cellulose- digesting flagellates in termites (Breznak and Brune, 1994) and wood roaches and of ciliates in the digestive systems of ruminants, or as the etiological agents of widespread human and animal diseases (Nisbet, 1984). Most Protozoa have attributes characteristic of higher animals, e.g., motility, in at least some phase of their life cycle, and acquisition of nutrients by ingestion (phagocytosis or pinocytosis). Some, however, are capable of photosynthesis, active transport, or diffusion, and there are examples among the euglenoids (Lee et aL, 1985) and dinoflagellates (Bochstahler and Coats, 1993) of organisms capable of living both autotrophically and heterotrophi- cally. In addition to these methods for obtaining nutrients, some ciliates MAINTAINING CULTURESFOR BIOTECHNOLOGYAND INDUSTRY Copyright 91996 by Academic Press, Inc. All rights of reproduction in any form reserved. 133 134 Ellen M. Simon and Thomas A. Nerad have the means to adopt a cannibalistic life style. Most species of Tetrahy- mena ingest bacteria, absorb nutrients from axenic media (containing no other organisms); other species, by transforming into macrostome cells, can also ingest other tetrahymenas.

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  Principles of Veterinary Parasitology

  • Dennis Jacobs, Mark Fox, Lynda Gibbons, Carlos Hermosilla(Authors)
  • 2015(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  CHAPTER 4 Protozoa (single-celled parasites)

  1. 4.1 Introduction
  2. 4.2 Key concepts
     1. 4.2.1 Classification
     2. 4.2.2 Locomotion
     3. 4.2.3 Nutrition
     4. 4.2.4 Transmission
     5. 4.2.5 Reproduction
  3. 4.3 Ciliates
  4. 4.4 Amoebae
  5. 4.5 Flagellates
     1. 4.5.1 Haemoflagellates
        1. Trypanosoma
        2. Leishmania
     2. 4.5.2 Other flagellates
        1. Giardia
        2. Trichomonads
        3. Spironucleus
        4. Histomonas
  6. 4.6 Coccidia
     1. 4.6.1 General characteristics
     2. 4.6.2 Eimeria
        1. Life-cycle
        2. Epidemiology
        3. Pathogenicity
        4. Histopathology
     3. 4.6.3 Coccidiosis
        1. Avian coccidiosis
        2. Mammalian coccidiosis
  7. 4.7 Tissue cyst-forming coccidia
     1. 4.7.1 Sarcocystis
        1. Sarcocystis neurona
     2. 4.7.2 Besnoitia
     3. 4.7.3 Toxoplasma
        1. Life-cycle
        2. Pathogenicity
        3. Epidemiology
     4. 4.7.4 Neospora
        1. Bovine neosporosis
        2. Canine neosporosis
  8. 4.8 Blood-borne apicomplexans
     1. 4.8.1 Babesia
        1. Life-cycle
        2. Pathogenicity
        3. Epidemiology
        4. Babesiosis/piroplasmosis
     2. 4.8.2 Theileria
  9. 4.9 Cryptosporidia
     1. 4.9.1 Cryptosporidium parvum
        1. Life-cycle
        2. Pathogenicity
     2. 4.9.2 Avian cryptosporidiosis
  10. 4.10 AntiProtozoal drugs
      1. 4.10.1 Key concepts
      2. 4.10.2 Anticoccidial drugs
         1. Ionophores
         2. Sulphonamides

  4.1 Introduction

  Although Protozoa are single-celled organisms, they are not necessarily primitive. They have much greater complexity than other unicellular life-forms, such as bacteria. Like multicellular animals and plants, their DNA is mostly packaged into chromosomes within a nucleus. They have many subcellular structures similar to those in metazoan cells but, in addition, each Protozoan species possesses specialised organelles that enable it to live and function as an independent organism within its own ecological niche. Most Protozoa are free-living although many coexist with animal hosts. This chapter focuses on those that are potentially pathogenic. Many others are benign (‘commensals’) or even beneficial to their host, e.g. the symbionts that digest cellulose in the rumen or caecum of herbivores.

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  Microbiology

  • Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Brian M. Forster, Philip Lister(Authors)
  • 2016(Publication Date)
  • Openstax

    (Publisher)

  (credit: Centers for Disease Control and Prevention) Jump to the next Clinical Focus box. Clinical Focus 196 Chapter 5 | The Eukaryotes of Microbiology This OpenStax book is available for free at http://cnx.org/content/col12087/1.4 important in producing antimicrobial substances such as penicillin. In this chapter, we will examine characteristics of protists, worms, and fungi while considering their roles in causing disease. Figure 5.3 (a) A scanning electron micrograph shows many Giardia parasites in the trophozoite, or feeding stage, in a gerbil intestine. (b) An individual trophozoite of G. lamblia, visualized here in a scanning electron micrograph. This waterborne protist causes severe diarrhea when ingested. (credit a, b: modification of work by Centers for Disease Control and Prevention) Characteristics of Protists The word protist is a historical term that is now used informally to refer to a diverse group of microscopic eukaryotic organisms. It is not considered a formal taxonomic term because the organisms it describes do not have a shared evolutionary origin. Historically, the protists were informally grouped into the “animal-like” Protozoans, the “plant- like” algae, and the “fungus-like” protists such as water molds. These three groups of protists differ greatly in terms of their basic characteristics. For example, algae are photosynthetic organisms that can be unicellular or multicellular. Protozoa, on the other hand, are nonphotosynthetic, motile organisms that are always unicellular. Other informal terms may also be used to describe various groups of protists. For example, microorganisms that drift or float in water, moved by currents, are referred to as plankton. Types of plankton include zooplankton, which are motile and nonphotosynthetic, and phytoplankton, which are photosynthetic. Protozoans inhabit a wide variety of habitats, both aquatic and terrestrial.

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  Soil Sampling and Methods of Analysis

  • M.R. Carter, E.G. Gregorich, M.R. Carter, E.G. Gregorich(Authors)
  • 2007(Publication Date)
  • CRC Press

    (Publisher)

  Chapter 36 Protozoa S.M. Adl Dalhousie University Halifax, Nova Scotia, Canada D. Acosta-Mercado University of Puerto Rico Mayaguez, Puerto Rico D.H. Lynn University of Guelph Guelph, Ontario, Canada 36.1 INTRODUCTION Among the microbial groups, Protozoa are involved in pivotal processes in both aquatic and terrestrial ecosystems. In soil ecosystems, Protozoa are conspicuous (Berthold and Palzenberger 1995), serving as consumers and prey for other soil microorganisms (Clarholm 1981), influencing the development and metabolic activities of bacterial communities (Pussard et al. 1994; Griffiths et al. 1999), and concomitantly increasing plant biomass (Kuikman et al. 1990; Alphei et al. 1996). The role and diversity of Protozoa in the soil has been the subject of recent reviews (Adl 2003; Adl and Gupta 2006). An extensive literature was synthesized in two earlier reviews (Foissner 1987; Darbyshire 1994), and Bonkowski (2004) reviewed the interactions of Protozoa with plant roots. Protozoa are defined as heterotrophic, nonfilamentous protists. The major role of Protozoa in decomposition food webs is usually assumed to be as bacterivores. Although this is primarily correct, Protozoa consumers are more diverse, influencing the rest of the food web by feeding on each other, fungal components, and even on some soil metazoans. Ingestion of prey through a cytostome in smaller Protozoa, like nanoflagellates, is usually one bacterium or protist at a time. In larger species with a cytostome, particularly larger ciliates, ingestion of hundreds of bacteria or several protists occurs at the same time in one food vacuole. A few amoeboid genera, a couple of ciliate genera, and some testate amoebae can ingest fungal hyphae or the cytoplasm of hyphae and spores. These genera are fungivorous and cultured or baited on spores or hyphae. The Eumycetozoa (slime moulds) are primary saprotrophs that digest woody or cellulosic substrates, such as bark, leaf litter, wood, or dung. 455

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  Cell Physiology Sourcebook

  A Molecular Approach

  • Nicholas Sperelakis(Author)
  • 2001(Publication Date)
  • Academic Press

    (Publisher)

  SECTION VII P r o t o z o a a n d B a c t e r i a This page intentionally left blank Michael Levandowsky and Thomas E. Gorreil Physiological Adaptations of Protists I. Introduction This chapter introduces the reader to the great diversity to be found in the physiology of the single-celled eukaryotes, or protists. These include a variety of groups, some auto-trophic or plant-like, some phagotrophic or osmotrophic and thus animal-like, and many with a combination of these traits. First, a word about terminology and classification. Trad-itionally, these organisms comprised the algae and the pro-tozoa. The early classifications of Protozoa divided them into three groups based on their locomotion (ciliates, flag-ellates, amoebae) and a parasitic group (sporozoa). The algae were classified largely on the basis of pigments (red algae, brown algae, golden-brown algae, green algae) and obvious structural differences (cryptophytes, di-noflagellates). Many of the flagellated groups appeared in both classifications. These characteristics are clearly im-portant, and the early classifications and terminology tend to persist in informal usage. However, subsequent work with the electron microscope, biochemical advances, and molecular approaches have changed many of our views on phylogenetic relationships, and revised classification schemes have been proposed (Cavalier-Smith, 1993; Patterson 1994). In this chapter, the term Protista, or simply protists, is used to describe all of these groups. Figure 1 gives an infor-mal indication of current thinking about relationships among protistan and other eukaryotic groups, as indicated by molecular evidence, particularly rRNA homology (Sogin, 1989, 1991) as well as ultrastructural information. Molecular and other evidence suggests that many protist lines may have originated over a billion years ago.

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  The Changing Wildlife of Great Britain and Ireland

  • David L. Hawksworth(Author)
  • 2003(Publication Date)
  • CRC Press

    (Publisher)

  et al. 1997). But Protozoan (and microbial) ‘biodiversity’ is quite different in character to that of macroscopic animals and plants (e.g. with respect to the ubiquity of individual species) and the most fruitful explorations in this area will be those that seek better understanding of Protozoan (and microbial) diversity as integral components of ecosystem function.
• As soil Protozoa are now recognised as being economically important, it is likely that more attention will be devoted to obtaining solid information about their identities, population dynamics and general ecology.
• It is unlikely that ‘mapping schemes’ will be initiated for free-living Protozoa in Britain.
• The common ground between taxonomy and ecology of Protozoa is fertile territory for scientific research, and many fundamental questions need to be answered. What is a species? Can molecular techniques be useful in refining species concepts? To what extent are genotypic and phenotypic characters correlated in Protozoa? Can we define a Protozoan ‘niche’, and what is the ecological significance of sibling species?

ACKNOWLEDGEMENTS

I should like to thank the following for assistance in providing information and helpful criticism: Peter Burkill, Colin Curds, John Corliss, John Darbyshire, Jackie Parry, Andrew Gooday, Fionna Hannah, Harriet Jones, Johanna Laybourn-Parry, Barry Leadbeater, Ray Leakey, John Murray, Franco Novarino, David Patterson, Terry Preston, Andrew Rogerson, Michael Sleigh, Humphrey Smith, Sue Tong, Keith Vickerman, Alan Warren; and thanks to Ian McCulloch and Carolyn Williams, the librarians at Ferry House.

REFERENCES

Bernard, C. and Fenchel, T. (1996) Some microaerobic ciliates are facultative anaerobes. European Journal of Protistology, 32, 293–297.
Berninger, U.-G., Finlay, B.J. and Kuuppo-Leinikki, P. (1991) Protozoan control of bacterial abundances in fresh water. Limnology and Oceanography, 36, 139–147.
Bütschli, O. (1880–89) Protozoa, in Bronn, H.G. (ed.) Klassen und Ordnungen des Tierreichs