Protozoans Flashcards
Protozoans
- Unicellular, eukaryotes without a collagen and chitinous cell walls
- animal like organisms
- mostly heterotrophs
- hypothesized that flagellates protozoans are animal ancestors
Do protozoans go under photosynthesis
Not in the primitive condition
Do protozoans develop from the blastula embryonic stage like animals?
No
How do protozoans live and obtain food
Most are free living organisms that obtain food from decaying organic materials or feed on bacteria and smaller eukaryotes
-some are parasites/ pathogens
How many species of protozoans are identified
40000
In protozoans the single cell functions as a ___
Whole organism
-therefore they lack specialized organelles for respiration, digestion and excretion
Size of protozoans
Microscopic
-5-250 nano meters or smaller
What are 3 ways protozoans can live
Free living
Parasitic (cause disease)
Commensal (association with each other)
Where do protozoans live
Inhabit moist environments
Surface covering of protozoans
Plasmalemma (cell membrane)
-differentiated into ectoplasm (outer clear gelatinous region) and endoplasm (inner fluid region containing cell organelles)
Unique organelles of protozoans that are not found in most metazoans
- Contractile vacuole
- Spongiome
- Trichocyst
- Toxicyst
Contractile vacuole
Used for osmoregulation (release water from the cytoplasm, maintaining concentration and osmotic gradient in cells)
Spongiome
Collection of vesicles and tubules for fluid collection storage in the cytoplasm
-connects contractile vacuole for expelling water out of the cell
Trichocyst
Elongated capsule-like filament released in response to mechanical or chemical stimulus. Protect against predation and aid anchorage during feeding.
Developed in membrane bound vesicles in the cytoplasm, lie around the peripheral of the cell and released to the surface as extrusomes
Toxicyst
Toxins for paralyzing prey and initiating digestion
Non functional and functional vacuole in cell osmoregulation
Non functional: allows excess fluid into a cell, resulting in increased cell volume and reduced cytoplasmic solute concentration
Functional: allows water influx but loses both water and solute, decreasing cytoplasmic solute
Functional: regulates influx and efflux of water, maintaining cell volume and cytoplasmic solute concentration
Extrusomes
For injecting prey with mucus, toxins (Toxicyst) when released
Stimulated in response to feeding (catching prey) or defending or attaching to substrate
Common locomotor organelles utilized by free living protozoans:
Cilia (paramecium)
Flagella (euglena)
Pseudopodia (amoeba)- flowing extensions of cytoplasm
Cilia
-short, hair like structures found on the surfaces of protozoa called ciliates (phylum ciliophora)
-cylindrical in shape and arise from basal body called a kinetophore
-can be distributed more or less uniformly all over cell surface, in rows or patches or grouped in tufts (cirri-walk or jump on solid surfaces)
-used for swimming and allow ciliated to move smoothly through water or even jump
-capable of whip like logon coordination by microtubule arranged in cell membrane
-
Cilia cross section anatomy
Inside each cilium contains long fibers called microtubules made up of proteins known as tubulin.
Each cilium is surrounded by the cell membrane and is supported by a cytoskeleton of microtubules arranged in a 9 doublet +2 pattern
The whole microtubules complex containing the 9 doublet +2 central sheath is called an axoneme
Flagella
- long, while like structures found on the surfaces of many protozoans
- typically for locomotion and feeding
- shared similar cross section to cilia.
How does flagella differ from cilia
- bearing hairlike projections on its surface (mastigonemes) which increase surface area and enabling greater propelling through water.
- flagella usually fewer and longer than cilia
Pseudopodia
(False feet)
- characteristic of the amoeba group of protozoans
- important in locomotion and feeding whereby protozoan flows in its intended direction by cytoplasmic steaming
- movement of Pseudopodia is mediated by a controlled transition of gelatinous ectoplasm (gel) and fluid endoplasm (sol)
- Pseudopodia vary in size and shape but are like cilia and flagella are surrounded by the cell membrane and often supported by microtubules (not 9+2)
Pseudopodia variant’s
Lobopodia: broad, rounded lip and finger like
Filopodia: threadlike, slender and often branched
Reticulopodia: forms highly reticulated (branched) of extremely thin filaments
Anxiopoda: thin rods composed of microtubules
How can Protozoan reproduce
Both sexual and asexual though asexual is more common
Asexual reproduction requirements of protozoans
-requires mitosis (separation of chromosomes) and cytokineses (separation of cytoplasm)
Types of asexual reproduction amount protozoans
Binary fission
Schizogony
Budding
Plasmotomy
Binary fission
Process involving the separation of the cytoplasm across the long axis of the cell. Most protozoans reproduce by binary fission
Schizogony
Or multiple fission is a process invoking the splitting of one cell into many daughter cells. Sporozoans in the genus plasmodium reproduce by means of Schizogony while inside humans blood cells
Budding
Unequal division of the protoplasm and results in the formation of a bud at the margin of a cell. If conditions are favourable, the bud will grow and eventually separate from the cell, but if conditions are poor, the bud may die with little consequence to the cell.
Plasmotomy
Splitting of the parent into two; without mitotic division with the nuclei distributed between the two daughter cells
Sexual reproduction among the protozoans
Involves interaction with other, genetically different protozoans. May involve mainly syngamy and conjugation
Syngamy
Involves the fusion of two haploid cells to form a diploid zygote. Protozoa in the genus plasmodium undergo syngamy while inside mosquitos
Conjugation
Requires that two cells with different genetic content meet and position themselves side by side. Portion of the cell membranes fuse allowing the formation of a cytoplasmic bridge and then segments of genetic material (DNA) are exchanged between the two cells.
-each now carries new genetic material as they separate
Protozoans are classified as ____ by how they feed
Holozoic (heterotrophic) or organisms that take in whole organisms for food as they have no means of biting off small portions of their prey
In protozoans, structures used in locomotion are also used in
Feeding and food gathering as well as ingestion and digestion
How do protozoans digest
Digest intracellularly forming a food vacuole or phagosome prior to enzymatic digestion
Cytosome
Cell mouth
A region on the surface of. Protozoan where endocytosis can occur
Lysosome
Contain digestive enzymes needed to break down food materials taken in through endocytosis
Cilia and flagella in feeding
The structures can sweep food along the cell surface toward the cytosome and sometimes line a region of the cell called an oral funnel or oral groove
Pseudopodia in feeding
Amoeba- like protozoans use their Pseudopodia to capture food by extending them out and around the food and fusing them to form food vacuoles prior to digestion
Euglena and chlamydomonas can live as both
Plants and animals
Paramedics use cilia to beat _____ current
Against
Protozoan classification types
Ciliophora (cilia)
Mastigophora (flagella)
Sacodina (Pseudopodia)
Sporozoans/ Apicomplexia (spore forming)
In protozoans classification the kingdom protozoa is now split between two kingdoms
Chromista and protozoa
Chromista: algae, diatoms, oomycetes and protozoans
Protozoa
Super phylum alveolates includes
Phylum ciliophora
Phylum Dinozoa (dinoflagillata)
Phylum apicomplexia
Super phylum rhizaria includes
Phylum foraminifera
Phylum radiolaria
Phylum cerozoa
Super phylum hererokonta includes
Phylum stramenopiles
Superphylum amoebozoa includes
Phylum mastigamoididae
Phylum eumycetozoa
Super-phylum excavata includes
Phylum parabasala
Phylum euglenozoa
And
Heterolobsea
Alveolates (alveolata)
Large group with unique membrane bound sacs known as alveoli, just below the outer cell membrane (ectoplasm)
Ciliophora general characteristics
- external body covering is covered with cilia at all or some stages of the lifecycle
- individual cilium are joined below the body surface via a complex cord of fibers (infraxiliature)
- all members of the group have at least one micro nucleus and a mega nucleus
- more advanced group of protozoans possessing the highest degree of sub cellular specialization.
Ciliophora habitat
- mostly free living
- variety of aquatic habitats, especially fresh water but also marine.
- form protective cysts to survive unfavourable conditions
Ciliophora are _____ in body plan
Uniform
Ciliophora are monophyletic meaning
Evolve from a common/single ancestor
Ciliophora can reproduce
Sexually by conjugation
Members of the ciliate family include
Paramecium, vorticella and stentor
Ciliate feeding
- possess cytostome (mouth) and throat like area called a gullet
- most feed on microorganisms and food vacuole forms at end of throat
- an unusual group are called the suctoria which can paralyze their prey (other protozoa) and suck out nutrients
- food stored in food vacuoles
- possess digestive enzymes for processing organic food
- freshwater specifies tend to take on water-must constantly pump out excess
Ciliate Trichocyst and pellicle
Possess Trichocyst: threadlike proteins that the protozoan is able to shoot out to anchor the cell or capture prey
Pellicle: complex series of membranes covering the surface of ciliates, provide support and maintains shape.
-mainly rigid, some flexible, depending on membrane organization
Trichocyst are closely associated with pellicle of ciliates
Ciliophora cilia function
- most are motile by means of cilia
- fastest of all protozoans
- some species have bundles of cilia which are fused to form rigid spines (cirri) for crawling on substrates
- a few are nonmotile and some of these are colonial, live attached to substrate by stalk. Cilia are used for filter feeding and not movement (vorticella)
Ciliate nuclei
Most have two types of nuclei (dimorphic; heterokaryotic)- small micro nuclei and large macro nuclei
Macro-nucleus and micro nucleus functions
Macro- has DNA and RNA
Involves in normal (metabolic) functions of the ciliate, differentiation of regeneration. Vital for survival of cell
Micro- more abundant: sexual reproduction
Can survive without micro but not macro nucleus
Ciliate conjugation reproduction
- sexual reproduction in ciliates involves conjugation
- temporary physical association between 2 ciliates for the exchange of genetic material
- exchange occurs via a tube formed form joining of the cytoplasm of both ciliates
- conjugation results in disintegration of macronuclei, while micronuclei divide meiotically to form four haploid pronuclei
- two cytoplasmic mitotic divisions result in 4 daughter cells from each parent (8 in total)
Binary fission reproduction in ciliates
Micronuclei undergo mitotic division and spread around the cytoplasm. Mega nuclei fuse to form a large mega nucleus which then divide cytoplasm split anterior and posteriorly into 2 halves giving rise to daughter cells.
Autogamy
Self nuclei division
- Macronucleus degenerates
- neurotic division of micronuclei followed by mitosis to form 8 pronuclei
- fusion of 2 pronuclei to form a synkaryon result in micro-and-macro nucleus
- cytoplasmic division result in 2 ciliates, similar to the parents.
Ciliate behaviours
Free living and motile (60%)
- holozoic: free living forms ingest food particulates
- raptorial: hint and ingest prey alive (Didinum nasutum)
- suspension feeders: Bacteria, unicellular algae, other protozoa
- some temporarily attach to substrates for feeding
- sessile: some attach permanently and may form colonies
- symbiotic: with other invertebrates and vertebrates
- commensal: attach to crabs surface
- endoparasite: fish, sea stars, horses, cattle
Phylum Dinozoa general characteristics
- are whirling protozoans
- possesses two flagella that are structurally distinct; one within a longitudinal groove (sulcus), other within a transverse groove (girdle), surrounding the body
- inhabit both fresh and salt water
- 2000 species
- about 50% possess chlorophyll (autotroph) form symbiont one tissues of foraminiferans and some metazoans marine invertebrates (reef-forming corals)
Phylum Dinozoa
- Bioluminescence
- toxicity
- neurotoxin
- biochemical production of light
- very toxic “red tide”: toxic to fish and crustaceans accumulate in tissues of some aquatic molluscs resulting in diarrhetic shellfish poisoning
- neurotoxin: some bottom dwelling species release toxins in fish predators (might not be toxic to fish), which could be toxic to humans when consumed
- Pfiesteria piscicida toxins: lead to mass death of fish in brackish water
- Hermatodinium perezi: are parasites of crabs causing death
Why are dinoflagellates in phylum ciliate
Molecular studies show that dinoflagellates are more closely related to ciliates and apicomplexians than other flagellated protozoans
Phylum Apicomplexia characteristics
- most infective species exhibit stages with distinct cluster of microtubules and apical complex at one end of the cell in some stages of life cycle
- over 6000 species
- most species are endoparasites in various animal groups: fairly complex life cycles
- all members of group are NONMOTILE
- lifecycles alternate between sexual and asexual reproduction, sometimes in two hosts in two hosts
Phylum Apicomplexia health impact
Parasite types
- parasites of the group result in huge human health impact
1. Babesis sp.
2. Plasmodium
Babesis sp.
(Texas fever)
- caused the death of 1000’s of cattle in US in late 1800’s and early 1900’s
- transmitted by ticks
- results in destruction of RBC’s, results in bloody (red) urine called “red water fever”
- currently almost completely eliminated by dipping cattle in pesticides to kill ticks
Plasmodium
(Malaria causer)
- several species such as P. falciparum, P. vivas, P. malariae
- malaria has probably killed more people than any other disease in history
- chronic in some parts of world, mostly tropical
- infects 300-500M a year
- results in 450 000 deaths a year (death every 12 seconds)
- transmitted by mosquito vector
- requires two hosts to complete life cycle
Plasmodium life cycle stages
- Anopheles mosquito has sexual stages in its salivary glands (transmitted by mosquito bite)
- Humans Barbie the asexual stages in blood, especially RBC’s and liver
Symptoms of malaria
- cold and shivering 7-14 days post infection causing uncontrollable deep tremors take over the body
- fever follows (up to 106°) with profuse sweating, cyclic chills, fever, headache every 3-4 days
- infection can cause irreversible damage to liver, spleen, kidneys and brain
- infected persons may succumb by way of delirium and coma
- if not treated may be self limiting but host may be a reservoir for up to 3 years
Most effective way to eliminate malaria
Elimination of mosquito
- mosquitos have developed resistance to insecticides
- developed antibiotic resistance
- experimental vaccines in works
- some have developed genetic resistance (sickle cell disease)
Apicomplexia: Toxiplasma
- requires two hosts to complete life cycle
- toxoplasma is an example of zoonotic diseases
- cats are primary/ definite host
- rodents, cattle, sheep are intermediate hosts
- prey species such as rodents serve as intermediate hosts
- infected cards release cysts in feces
- to spread toxoplasma manipulates rodents brains making them reckless and more likely to be caught by cats
Can toxoplasma parasites infect humans
Sometimes humans can become intermediate hosts
Humans acquire infection through contaminated soil, cat feces, and infected meat.
Generally non human to human transfer
16% of US adults are infected often asymptomatic in adults. Children sometimes get rash
What does the toxoplasma do in humans
Inside humans, the parasite can invade the blood and multiply in WBC’s and various organs.
- congenital infection: if contracted by pregnant women especially in first trimester, the parasite can cross placenta and cause retardation blindness convulsions in embryo, fetus or newborn.
- 2% of all mental retardation in US may be due to prenatal Toxoplasma exposure
Amoeba General characteristics
To change form
- Protozoans that move by characteristic Pseudopodia (false feet)
- can alternate between solids gel-like (cytogel) and liquid cytoplasm (cytosol) to produce Pseudopodia
- about 56000 species have been identified
- no cilia, pellicle, or double nuclei
- contractile vacuole is not fixed in position like ciliates
Pseudopodia can serve as both
Locomotion
English food
Or both
Can amoeba conjugate
Nope
Amoeba behaviour
- most are free living
- 2% are parasites Ex: Entamoeba histolytica (100 000 deaths yearly)
- some act as parasite of other parasites (hyperparasitism)
Amoeboid reproduction
- mainly asexual by binary or multiple fission
- sexual: individual form gamete and fuses with another forming gamete
Encystment
Can occur in free living and parasitic species during unfavourable conditions
(Amoeboid)
Amoebozoans
Subgroup of Amoeboid s
- contains thousands of species with Amoeboid movement
- mostly free living, some parasitic
- most possess branching tubular mitochondrial cristae, hence they may be known as “naked ramicristate amoeba”
Entamoeba histolytica parasite
- live in large intestines of humans and animals
- infected by ingesting the cyst form contaminated water or veggies
- in the stomach and duodenum, cyst walls are digested away allowing the trophozoites (larvae stage, four per cyst) to be released
- trophozoites live in the caecum and reproduce by binary fission
- most cases cause minimal harm to host, and live off material passing through host.
- symptoms may develop within days and last up to a year
- 10% of cases, the parasite invade the intestinal mucosa causing tissue lysis and ulceration resulting in dysentery.
- in severe infection may induce secondary bacterial infections when they penetrate the sun mucosa and serous membrane to enter peritoneal cavity.
- cause cramps, nausea, and diarrhea
- can cause severe symptoms of dysentery, abdominal tenderness, dehydration and general incapacitation
- in rare cases amoeba travel through portal system to the liver causing amoebic hepatitis
Naked Amoeba (gymnamoeba)
- shape
- species number
- habitat
- shapeless, wide, blunt or thin pointy Pseudopodia
- shape changes frequently based on movement of the organism
- over 200 species have been described
- most are free-living in freshwater, estuaries and marine
Naked Amoeba feeding
-all are heterotrophic, capture prey with the aid of Pseudopodia; ingestion involves…
- phagocytosis (bacteria)
- pinocytosis (taking in fluid with smaller food particles)
- parasitic to other invertebrate
Superphylum Rhizaria
- members possess thin Pseudopodia (filopodia), supported by microtubule in some species
- Pseudopodia may be simple or branching forming a complex network known as reticulopodia
- two important groups: foraminiferans and radiolarians
Phylum foraminiferans
- habitat
- produce
- Pseudopodia
- produce calcium carbonate shells
- Pseudopodia (reticulopodia) protrude through pores and branched extensively to form dense networks.
- most are marine species and live on the ocean floor in large numbers
- some are found on water surface (planktonic)
- very abundant in ocean floor: form thick “oozes” that cover a third of the deep ocean floor
Foraminiferans
-reproduction
-most reproduce asexually but a few do sexual
Foraminiferans fossils
- extensive fossil record
- over 30 000 species identified
- 80% extinct
- fossils are used as blackboard chalk, cement, indicator of crude oil
Foraminiferans feeding
Feed on dentritus, protists, bacteria, fungi and small metazoans
Foraminiferan diversity
Globigerina bulloides Globigerinoides ruber Stainforthia concava Calcarina guadaudichaudi Elohidium crispum Polystomella strigullata
Phylum Radiozoa (Radiolarians)
-include radiolarian and Acantholaria
- Rasiolaria secrete a silica shell
- body is organized into 2 distinct zones:
1. Extracapsular zone (vacuolated)
2. Inteacapsular zone
Radiozoa Pseudopodia
Pseudopodia is supported with thin, radiating microtubules giving a spiny, rayed appearance in many species.
Pseudopodia+microtubule support=axopodia
Members of the Radiozoa have a rigid _____
Endoskeleton made up of silica (radiolarians) or strontium sulfate (acantharians)
Phylum Radiozoa fossil
- fossils prominent for the presence of silica-containing skeletons, similar to the shelled amoebae and foraminiferans)
- 7700 of the 8700 species are only known as fossils
- 160 species of acantharians
Phylum Radiozoa behaviour
- most radiolarians and acantharians are planktonic (passive drifting along water current)
- most species form symbiont with algae for nutritional benefit via photosynthesis
- some are carnivorous (feed on microscopic prey)
Phylum Heliozoa
- body is divided into distinct inner and outer regions, not separated by physical boundary (lack of a capsular membrane); axonemes have many microtubules organisms into hexagons or triangles
- are planktonic (floating with axopodia)
- axopodia function in food capture; in some species for locomotion
Flagellated protozoans unique characteristics
- possess a pellicle (provide shape)
- possess one to many flagella
- cytostome present (not complex as in ciliates)
- cintrxcilt caculoe may be present-fixed within the cytoplasm (fresh water species)
- most are free living and motile
- members may be either photosynthesizing, particle feeding and parasitic species
Flagellated are ancestors of
All amoeba- like protozoans
Flagellated were formally known as
Mastigophorans
Flagellated protozoans: classification
Broad categories into 2:
- phytoflagellata
- zoo flagellata
Phytoflagellata
Plant like flagellated
- photosynthesizing flagellated protozoans
- possess chlorophyll, using carbon dioxide to obtain energy from sunlight.
- lack of a mouth or food vacuole
- some wuglenoids may become heterotrophs in dark conditions-ingest solid foods like animals
Phytoflagellates
-most possess a red____
Red cup shaped light sensitive organelle known as a stigma
-flagella and stigma help to maintain the organism in shallow water to access sunlight
Zooflagellata
- most are animal-like flagellates
- are free-living in fresh water, marine/salt or soil
Choanoflagellates
Important group of zooflagellates
- freshwater species
- sessile (live attached permanently)
- members have a single-flagellum that forms part of the length of the body through a cylindrical network of protoplasm in strands known as microvilli
Flagella in zooflagellata create
Feeding current for pushing food into the collar for ingestion
Genus Proterospongia from the Zooflagellata
Are planktonic an complex, having 100’s of cells like the primitive sponges
Health implication of Zooflagellates
- 25% of members live as commendable or parasites in plants and animals including humans
- parasitic members vary in structure and complexity from other flagellated
- important member is the genus: Trypanosoma (cause sleeping sickness disease in humans
- some species cause diseases in plants and mammals (cattle, sheep, goat, horses and other domesticated animals)
- lifecycle is complex and adapted to parasitic life style
- have a KINETOPLAST (DNA for synthesis of mitochondrial proteins), sited near a single, large mitochondrion
Parasitic Zooflagellates in humans
- Trypanosoma: cause sleeping sickness, coma and death
- T. beucei- cause African trypanosomiasis, transmitted by insect
- T. cruzi-American trypanosomiasis
- Leishmania donovani: cause intense disfigurement and high death rate
- Giardia lambdi: intestinal disorder
- Trichomonas
- T. vaginalis: Urogenital tract infection
Trichomonas
Trichomonas vaginalis: small sized parasitic protozoans
- T. vaginalis
- T. tenax
T. vaginalis
- infect humans vagina, urethra and prostrate
- caused little harm to men but significant irritation and discomfort in women
- some women develop infection with frothy, smelly, green discharge and painful urination
- 20-40% of infection worldwide
- one of the most common infections in the US with 2.5M a year
- lives in human Urogenital tract: enjoys the acidity of female tract
- 50% are asymptomatic carriers
- transmitted by sexual contact or contaminated toilets, occasionally spread in communal baths
- if acid balance is disturbed by other infections it can become more virulent
T. tenax
- lives in mouth, is not a pathogen (commensal)
- 5-10% oral infections, especially with poor oral hygiene
Giardia lamblia
Giardia lamblia: one of the causes of “travellers diarrhea”
- intense nausea and cramps
- one of the most common intestinal parasites in the world
- 20% of all humans infected
- CNS infect cattle, cats, bears, coyotes, birds and amphibians
- transmitted through consuming contaminated food or water
- especially common in poor overcrowded areas with poor sanitation and lack of clean water
- cysts shed in feces; fecal/ oral transmission
- can also be transmitted in ponds and pools
- cysts can survive up to two months in water
- chlorine doesn’t always kill cysts
- once infested Giardia infects the host small intestine
Symbiotic/ commensal flagellates
- complex flagellate species known as hypermaatigotes
- fork commensals with termites, cockroaches and wood roaches
Trichonympha campanula
Flagella?
Can make up 30% of termite biomass
Possibly help with cellulose digestion in termite gut
Termite may die in the absence of this parasite
Has over 10000 flagella
T. cruzi prevalence
- alternates between the reduviid bug and humans
- Mexico, Central America, South America
- 40-50% of pop of S. America
- 2-3M chronically infected and 45000 die a year
- most serious in children under 5
T. Cruzi life cycle
reservoir hosts are rodents, Opossums and armadillos
- transmitted when the “kissing bug” bites (usually on the lips)
- bug usually defecates after feeding
- when the bite is scratched, some of the infected feces is rubbed into wound causing infection
- amastiogotes form within mono cysts in subcutaneous cells
- tryopomastigotes released into bloodstream and eventually infested by bug
Symptoms of T. cruzi
- edema at the site of infection with alter development of acute headache, fever and sometimes severe skin lesions
- may also affect organs: brain, heart and intestines
- chronic infection may cause enlargement of the liver, spleen and lymph glands, with anemia and nervous system disorders
Prevention of T. cruzi
Elimination of vectors (bug)
Apicomplexabs have a specialized arrangement of organelles called the…
Apical complex at some time during life cycle
Used to burrow into host
Which amoeboid is multinucleated and large?
Chaos carolinensis
