What Type of Animal-like Protist Is Giardi

Parasitic Protists

Parasitic protists synthesize a range of glycans and glycoconjugates that are constituents of cell surface coats, cyst walls and intracellular carbohydrate reserves.

From: Microbial Glycobiology , 2010

Glycosylated compounds of parasitic protozoa

Joanne Heng , ... Malcolm J. McConville , in Microbial Glycobiology , 2010

Summary

Parasitic protists belong to a range of securely diverging eukaryotic taxa and are the cause of many important diseases in humans. These organisms are capable of surviving in multiple vertebrate and arthropod host environments and, in some cases, as free-living organisms. All parasitic protists limited a range of glycoconjugates that form protective protein-rich or carbohydrate-rich surface coats. Poly peptide-rich coats are typically found on developmental stages that inhabit non-hydrolytic niches, such every bit the bloodstream and non-acidified intracellular vacuoles. These coats are commonly dominated by a limited repertoire of antigenically diverse proteins that are commonly, but not always, glycosylphosphatidylinositol- (GPI-) anchored and modified with N- or O-glycans. Carbohydrate-rich coats are commonly found on developmental stages that dwell within hydrolytic environments, such as vertebrate and arthropod digestive tracts and lysosomal vacuoles. These coats are dominated by GPI-anchored glycoproteins that are heavily modified with N-glycans, O-glycans or phosphoglycans. Free GPI glycolipids (not fastened to protein) tin besides be abundant or dominant components of these coats. Some parasitic protists tin besides course highly resistant cyst stages encased inside polysaccharide-rich cell walls. Considerable progress has been made in defining the structures of the surface and intracellular glycans of the parasitic protists, their biosynthesis and the role that individual components play in parasite infectivity.

Keywords: Protozoan parasites; N-Glycosylation; O-Glycosylation; Glycosylphosphatidylinositol; Phos-phoglycosylation

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9780123745460000122

Microtubules: in vivo

Scott C. Dawson , Susan A. House , in Methods in Cell Biology , 2010

Abstract

Giardia intestinalis, a common parasitic protist, possesses a complex microtubule cytoskeleton critical for cellular function and transitioning between the cyst and trophozoite life cycle stages. The giardial microtubule cytoskeleton is comprised of highly dynamic and stable structures. Novel microtubule structures include the ventral disc that is essential for the parasite's zipper to the intestinal villi to avoid peristalsis. The completed Giardia genome combined with new molecular genetic tools and alive imaging will assistance in the label and analysis of cytoskeletal dynamics in Giardia. Primal areas of giardial cytoskeletal biology remain to be explored and noesis of the molecular mechanisms of cytoskeletal functioning is needed to better understand Giardia's unique biology and pathogenesis.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/S0091679X10970179

Giardia and Giardiasis, Part B

Kari D. Hagen , ... Scott C. Dawson , in Advances in Parasitology , 2022

Abstract

Giardia lamblia is a widespread parasitic protist with a complex MT cytoskeleton that is critical for motility, attachment, mitosis and cell partition, and transitions between its two life wheel stages—the infectious cyst and flagellated trophozoite. Giardia trophozoites have both highly dynamic and highly stable MT organelles, including the ventral disc, eight flagella, the median torso and the funis. The ventral disc, an elaborate MT organelle, is essential for the parasite's zipper to the intestinal villi to avoid peristalsis. Giardia'due south four flagellar pairs enable swimming move and may also promote attachment. They are maintained at unlike equilibrium lengths and are distinguished past their long cytoplasmic regions and novel extra-axonemal structures. The functions of the median body and funis, MT organelles unique to Giardia, remain less understood. In addition to conserved MT-associated proteins, the genome is enriched in ankyrins, NEKs, and novel hypothetical proteins that also associate with the MT cytoskeleton. Loftier-resolution ultrastructural imaging and a current inventory of more than 300 proteins associated with Giardia's MT cytoskeleton lay the groundwork for time to come mechanistic analyses of parasite attachment to the host, motility, cell sectionalization, and encystation/excystation. Giardia's unique MT organelles exemplify the capacity of MT polymers to generate intricate structures that are various in both form and part. Thus, beyond its relevance to pathogenesis, the report of Giardia'southward MT cytoskeleton informs basic cytoskeletal biological science and cellular evolution. With the availability of new molecular genetic tools to disrupt gene function, we anticipate a new era of cytoskeletal discovery in Giardia.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/S0065308X19300764

Physiological Adaptations of Protists

Michael Levandowsky , in Cell Physiology Source Book (Quaternary Edition) , 2012

VIIA Rhoptries

A large group of medically important parasitic protists, the Apicomplexa (formerly the Sporozoa), is divers past a structure called the apical circuitous. This group includes such important parasites as Plasmodium, which causes malaria. All the apicomplexa are obligate intracellular parasites at some stage in their life cycle and the apical complex is thought to exist an instrument of invasion. A prominent function of this complex are the rhoptries, secretory organelles containing lipids and proteins (Fig. 49.7) that originate in the Golgi system, filled with enzymes. For many years, the general assumption has been that rhoptry and microneme secretions must play a role in the invasion of the host prison cell, only information technology has proven difficult to identify bodily function (Sam-Yellowe, 1996). In some apicomplexid species, the parasite is independent in a parasitophorous vacuole afterwards invasion but, in others, the vacuole disappears and the parasite is in straight contact with the host cytoplasm. Rhoptries comprise dense protein granules and epitopes corresponding to these have been identified in the host cell membrane, its cytoskeleton and also in the parasitophorous vacuole membrane, where nowadays. Their role, nevertheless, is non articulate.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9780123877383000494

Unusual Functions for the Autophagy Mechanism in Apicomplexan Parasites

Maude Lévêque , Sébastien Besteiro , in Autophagy: Cancer, Other Pathologies, Inflammation, Immunity, Infection, and Aging , 2016

Introduction

Apicomplexa is a big phylum of parasitic protists belonging to the Alveolata grouping, together with ciliates and dinoflagellates. Several of its members are causative agents of man diseases. Malaria, which is caused by members of the genus Plasmodium, is a major global health trouble resulting in more than half a 1000000 of deaths per twelvemonth (White et al., 2014). Like many other apicomplexan parasites, Plasmodium has a complex life cycle. Sporozoites are transmitted from a mosquito vector to mammalian hosts and first multiply in the liver to produce merozoites, which will initiate crimson claret cell infection. Clinical manifestations of malaria are straight caused past the repeated cycles of parasite growth in erythrocytes inducing, in severe cases, chronic anemia, liver dysfunctions, and often fatal complications such as cognitive malaria.

Other important apicomplexan parasites affecting humans include Toxoplasma gondii and Cryptosporidium parvum, which are known to be opportunistic pathogens. T. gondii is the causative agent of toxoplasmosis, and is able to infect and persist in multiple tissues, including the brain and muscles (Montoya and Liesenfeld, 2004). Humans are infected through the consumption of cysts present in undercooked meat, or through oocyst-contaminated water or soil. Sporozoites independent in oocysts are transformed, subsequently ingestion, into tachyzoites, a highly invasive and replicative form responsible for the symptoms of the disease. The force per unit area of the host immune response induces a switch to the bradyzoite latent form, which persists within the host for its unabridged life. Infections are usually asymptomatic, but tin cause severe ocular and neurological disorders in cases of congenital toxoplasmosis and in immunocompromised individuals.

Cryptosporidium parasites infect the gastrointestinal epithelium and cause cryptosporidiosis, a parasitic affliction of the mammalian intestinal tract inducing watery diarrhea (Checkley et al., 2015). Transmission of C. parvum occurs mainly through contact with contaminated water and, occasionally, food sources. Much similar T. gondii, infection in immunocompetent individuals is usually self-limiting just the main brunt occurs in conjunction with HIV infection.

Most Apicomplexa are obligate intracellular parasites, with unique and complex life cycles. These unicellular eukaryotes are named later on their apical circuitous, an assembly of secretory organelles, involved in host cell invasion. Apicomplexan parasites (although Cryptosporidium species are i rare exception for that affair) harbor a peculiar organelle, chosen the apicoplast, which is essential for their survival (van Dooren and Striepen, 2013). Several metabolic pathways are associated with the apicoplast, including the synthesis of fat acrid, isoprenoids, and iron-sulfur clusters. This plastid, which has lost its photosynthetic ability, is believed to accept been acquired through secondary endosymbiosis, and as a consequence it is surrounded past four membranes.

Macroautophagy (usually only referred to as "autophagy") is a cocky-degradative procedure which tin exist activated in response to stresses, but is as well a housekeeping machinery for cellular homeostasis (Shibutani and Yoshimori, 2014). Information technology involves a double-membrane compartment called the autophagosome to sequester and degrade intracellular components after fusion with a lysosome. Autophagosome formation requires autophagy-related (ATG) proteins, many of which were originally identified in the yeast Saccharomyces cerevisiae. The core autophagic machinery is evolutionary conserved in most of the eukaryotic phyla, including early-branching eukaryotes such equally parasitic protists from the Alveolata group (Brennand et al., 2011). Even so, searches for human or yeast ATG homologues in these parasites' genome sequence databases reveal that these proteins appear to exist merely partially conserved in these organisms.

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128029367000167

Autophagy in Parasitic Protists

Sébastien Besteiro , in Autophagy: Cancer, Other Pathologies, Inflammation, Immunity, Infection, and Crumbling , 2014

Kinetoplastids

The group of kinetoplastids contains several flagellate parasitic protists, many of which accept complex life cycles and go through multiple differentiation stages in 2 different hosts. As these parasites encounter changing environments, autophagy has been suggested to play a function in the cellular remodeling that accompanies metabolic adaptations and morphological changes during their life cycles ( Brennand et al., 2012).

An example is the involvement of autophagy in the selective turnover of organelles post-obit metabolic changes. T. brucei cycles between an insect vector (the tsetse fly) and a mammalian host, where it resides in the glucose-rich bloodstream. Bloodstream forms rely heavily on glycolysis for free energy production, and to host this metabolic pathway they have evolved glycosomes, which are peroxisome-like organelles. Interestingly, during bloodstream forms' differentiation into brusk, stumpy forms, which are pre-adjusted to life in the tsetse wing, information technology has been suggested that glycosome turnover past autophagy and subsequent lysosomal degradation are involved (Herman et al., 2008). This is reminiscent of methylotrophic yeasts, which, when cultured in methanol and subsequently transferred to glucose medium, specifically dethrone by autophagy peroxisomes that are no longer needed for methanol metabolism (Tuttle and Dunn, 1995).

Both for T. cruzi and Leishmania, a significant remodeling occurs during the then-called metacyclogenesis procedure, where insect-borne parasite forms differentiate into pre-adapted infective forms. In vitro functional studies take shown that this process is protease- and autophagy-dependent for Leishmania (Besteiro et al., 2006; Williams et al., 2006) and for T. cruzi (Alvarez et al., 2008). For Leishmania, subsequent and extensive remodeling occurring in the macrophages of the mammalian host, where metacyclic promastigotes differentiate into the substantially smaller and aflagellated amastigote forms, also requires proteolytic and autophagic machineries (Williams et al., 2006).

In kinetoplastids, autophagy is also upregulated in response to stresses such every bit nutrient deprivation (Besteiro et al., 2006; Alvarez et al., 2008; Li et al., 2012). However, how the nutrient-sensing pathway is regulated is not precisely known. In eukaryotes, target of rapamycin (TOR) protein kinases act as a sensor that integrates the nutritional and energetic status, adjusting cell metabolism and growth. T. brucei contains, in addition to 2 canonical TbTORC1 and TbTORC2 complexes, an additional complex involved in parasite differentiation, highlighting an unexpected complexity in TOR signaling for these parasites (Barquilla et al., 2012). Although sequence similarity searches prove mostly that these parasitic protists display a reduced gear up of autophagic proteins, some parts of the pathway take been expanded and might exist more complex, as illustrated past the 25 members of the Atg8 cistron family contained in the Leishmania genome (Williams et al., 2009).

Interestingly, in response to food deprivation, the autophagic response seems to be promoting the survival of Leishmania promastigotes (Besteiro et al., 2006), although this might not exist the case for prolonged starvation in other kinetoplastids. For example, while displaying normal growth in vitro, T. brucei Atg mutants displayed a significantly improved viability during prolonged starvation, suggesting that cell death tin be mediated by autophagy in these conditions (Li et al., 2012). The function of autophagy is more often than not seen every bit positive, to support prison cell survival under intracellular or extracellular stresses, and so-called autophagic cell expiry is all the same a rather controversial issue that has and so far been exemplified past very express experimental bear witness (Denton et al., 2012). In kinetoplastids, it is currently unknown whether cell expiry mediated by autophagy could have a real physiological office or has only been characterized as a result of harsh in vitro starvation conditions.

Read total chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780124058774000123

Symbiosis and Parasitism

Burton J. Bogitsh , ... Thomas N. Oeltmann , in Homo Parasitology (Fifth Edition) , 2022

Touch on of Genomics

In 2002, P. falciparum became the outset parasitic protist to have its entire genome sequenced. The filarial worm B. malayi in 2007 represented the commencement human-infective multicellular organism so studied. After, the genomes of a number of parasites have become the discipline of intense sequencing. As data accumulates from such studies, the basis for the comprehensive cognition of the underlying genetic controls required for successful host–parasite relationships is becoming available. Such data also have the potential to provide targets for drug and vaccine development. Expansion of our agreement of the mechanisms that permit for immune evasion and drug tolerance may also come up to light. On a population basis, boosted information tin can provide insight relative to parasite development and epidemiologic dynamics. With this plethora of possibilities, information technology is not surprising that much of current research is full-bodied on the expansion of DNA sequencing over a big range of parasitic organisms. One of the major means to control the effects and the spread of diseases acquired by parasites is the use of reliable and sustainable intervention programs. The problem that arises with such programs is either that many drugs are not active confronting all portions of the parasite's life cycle or that drug-resistance occurs afterwards prolonged use of current protocols. These shortcomings require a continual search for new targets for drugs and vaccines and/or means to obviate the rise and continuance of resistant strains. To illustrate how electric current genomic studies can impact these aforementioned problems, we will hash out two approaches every bit examples. One approach is to seek those genes within the parasite's genome whose mutations tin be linked to resistance. The mutated gene(s) and so serves as a probe or warning sign that the parasite population is at a loftier gamble of developing resistance. Researchers can target this population and destroy resistant strains before they can take concur and spread whatsoever farther. Another approach is to seek proteins that are involved in a metabolic pathway that is essential for the parasite's existence and use them every bit potential targets for drugs or vaccines.

As models for examining the effectiveness of these approaches, nosotros will examine in subsequent chapters three parasites responsible for medically of import diseases. P. falciparum representing malaria (see page 111), South. mansoni representing schistosomiasis (see page 193), and B. malayi representing filariasis (encounter page 313).

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9780128137123000011

Sarcocystidae Poche, 1913, the Predator-Casualty Coccidia in Rabbits

Donald W. Duszynski , Lee Couch , in The Biology and Identification of the Coccidia (Apicomplexa) of Rabbits of the World , 2013

Besnoitia Henry, 1913, in Rabbits

Besnoitia is ane of the more obscure and little-studied parasitic protist genera, and because of this, we know very little about it. Although it has been known and studied for 100 years, our knowledge of the life history of Besnoitia species in wild animals is still incomplete, and at that place are no definitive morphological criteria to distinguish between Besnoitia species. We do know that members of this genus are cyst-forming coccidia with a complex two-host (predator-prey) life bike, similar to those of Sarcocystis and Toxoplasma, only with their own unique nuances. Intermediate hosts ingest sporulated oocysts when they forage and these oocysts release sporozoites in their gut, which penetrate various host cells and undergo merogony. First-generation meronts develop in the endothelial cells of blood vessels, while later generations develop primarily in fibroblasts of various organs and tissues, producing large (upwardly to 1 mm) intracellular cysts (= pseudocysts), without subdivisions, that are surrounded by a thick, laminated, nucleated cyst wall enclosing numerous pocket-sized bradyzoites. Thus, the near distinguishing morphological characteristic of this genus is the large bradyzoite-filled cyst that occurs in the connective tissues of the herbivorous intermediate hosts. When cyst-containing tissue is eaten by the definitive carnivore host, the bradyzoites are released, penetrate enterocytes of their intestinal tract and undergo (presumably) simply ane merogonous generation, which leads to gamete formation that gives rise to oocysts after fertilization occurs. Interestingly, the genus Besnoitia seems to exist unique in at least two respects: (1) the power of oocysts to initiate gametogenesis in the definitive host has been lost, the completion of the sexual cycle being dependent on the ingestion of tissue cysts from suitable intermediate hosts, and (2) these species may be successfully propagated asexually by mechanical transmission by blood-sucking arthropods.

Other than these features, little else is known about the life history, epidemiology or environmental of the species in this genus (Leighton and Gajadhar, 2001). We do know that the illness besnoitiosis, caused by Besnoitia species, has been recognized merely in intermediate hosts and the prevalence of infection is high in some host populations where clinical disease can and does occur; for example, besnoitiosis in cattle is of considerable economic importance in some parts of the world (e.g., Africa), only the relationship of these parasites to the population dynamics and health of other herbivorous hosts (both wild and domesticated) is non known (Leighton and Gajadhar, 2001). Probably the least distinguishing morphological characteristic of Besnoitia species is the structure of their sporulated oocysts, which have been documented on only a handful of occasions. They are similar to those of Toxoplasma by being small (< 20 μm), having two sporocysts each with four sporozoites, and being shed in the carrion in an unsporulated condition. Levine (1988) listed what he considered to be vii valid species of Besnoitia: B. bennetti, B. besnoiti, B. darlingi, B. jellisoni, B. paraguayensis, B. tarandi, and B. wallacei, while Leighton and Gajadhjar (2001) listed seven named species, but added B. caprae, while omitting B. paraguayensis. Unfortunately, the primary ground for distinguishing betwixt species of Besnoitia is the structure of the tissue stage(s) and the intermediate host(s) in which they are institute. No molecular piece of work yet has been done to assistance distinguish between these species; thus, all taxonomy inside the genus should be considered provisional until some cistron sequences can be used to more rigorously clarify their specific status. Besnoitia species from cattle have been transmitted to the European rabbit, O. cuniculus, on a number of occasions, simply take simply been isolated from naturally infected rabbits in rabbitries a few times.

Read total affiliate

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B9780123978998000081

New Insights into Roles of Acidocalcisomes and Contractile Vacuole Complex in Osmoregulation in Protists

Roberto Docampo , ... Sayantanee Niyogi , in International Review of Cell and Molecular Biological science , 2013

Abstract

While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Contempo work in i of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which commonly collects and expels excess water equally a mechanism of regulatory volume subtract after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes likewise accept an acidic calcium shop rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, nosotros review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and poly peptide trafficking.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780124076952000020

Giardia and Giardiasis, Part A

Carmen Faso , Adrian B. Hehl , in Advances in Parasitology , 2022

1 Introduction

Diarrheal diseases are the superlative 2nd and 5th causes of death in low and middle income countries (LMICs), respectively (WHO, 2013). Giardia lamblia (syn. intestinalis, duodenalis) is a ubiquitous and broad-spectrum Diplomonad parasitic protist responsible for the diarrheal disease known as giardiasis. Prevalence of giardiasis reaches and frequently surpasses xxx% in LMICs (Furness et al., 2000). As a event, this communicable disease is mainly a scourge of populations already confronted with a heavy burden of illness, often including other parasitic infections.

The life cycle of Grand. lamblia consists of ii main stages, the infectious and environmentally-resistant cyst class and the feeding but not-infectious trophozoite (Adam, 2001). Cysts are shed in faeces which, in atmospheric condition of poor sanitation, contaminate h2o. When ingested, a flagellated trophozoite precursor actively emerges from the cyst'southward solitude (excystation) setting the stage for colonization of the new host's small-scale intestine. In vivo and in vitro, trophozoites can be induced to phase-differentiate and get environmentally resistant. Encysting trophozoites secrete large amounts of cyst wall material to build a cyst wall encapsulating the parasite within in a state of incomplete cell division (encystation), (Faso et al., 2013a,b) and thus preparing for transmission to a new host. Giardia's simplified subcellular system consisting of but four identifiable subcellular compartments, namely, nuclei, endoplasmic reticulum (ER), peripheral vesicles (PVs) and mitosomes (Faso and Hehl, 2011), a pocket-size and compact genome (ca. 12 Mb), and minimal molecular machinery (Morrison et al., 2007), highlight this parasitic species' peculiar form of development by secondary reduction (Ankarklev et al., 2010).

In this affiliate, nosotros volition summarize and talk over the master recent advances in our understanding of Thou. lamblia's subcellular organization, including intra- and extra-cellular protein trafficking routes and functional aspects of organelle maintenance. Citing the tardily Christian de Duve, 1 of the founding fathers of cell biology (Bowers, 1998), we volition effort to compile a critical 'cytonaut's guide' to the Giardia jail cell. Finally, we will innovate topics and techniques in Giardia molecular and evolutionary cell biological science which are likely to concur heart-phase in future research efforts into the biology of this fascinating and deceivingly elementary cell.

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/S0065308X19300399