Transcript sleeping sickness

Kingdom Protista
• Sometimes called the “Junk drawer”
• Contains animal-like, plant-like and
fungus-like organisms
• Plankton (zoo-/phyto-/myco)
CHARACTERISTICS OF PROTOZOANS
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Unicellular
Eukaryotic
Basically Ingestive Heterotrophs
Lack cell walls but have definite shapes
Most are motile
Basically reproduce by asexual reproduction
Aerobic but some can live in anaerobic
conditions (ones living in digestive tracts)
Special structures:
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Macronucleus – controls metabolism
Micronucleus - involved in conjugation
Contractile vacuoles – maintains
Meostasis
Ingestion structures
Anal pore – excretion of wastes
Trichocysts – defense mechanism
HABITAT
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Majority of free-living
Marine, terrestrial & freshwater.
Some are parasites on algae to vertebrates
Make up the zooplankton in marine
ecosystems. Feed on phytoplankton
• Abundant in soil or on plants & animals
• Some live in guts of termites, roaches &
ruminants (cows)
DIFFERENT PROTOZOANS
Paramecium with trichocysts
Paramecium
Didinium
Vorticella
Stenor
PARAMECIUM
• Paramecium is a
small unicellular
organism.
• It is plentiful in
freshwater ponds.
STRUCTURE
Position Of Protists In The
Prokaryotic Kingdom
Classification
Classified by method of locomotion
• Mastigophora – have one or more flagella
- Have a flagella with a 9-2 microtubule
arrangement
- Flagella are polar & undulates, pushing
protozoan in opposite direction
- Longitudinal reproduction
i.e. Peranema,
Chilomonas
• Ciliata (Ciliophora)
- Have cilia.
- Similar in structure to flagella but shorter and
all
over surface of organisms
- Cilia usually arranged in rows & connected to each
other
- Cilia near oral cavity involved w/ food getting
- Transverse fission, & sexual repro by conjugation
Ie – Paramecium, Didinium, Blepharisma,
Vorticella, Stentor
• Sarcodina
- Use Pseudopods for movement
- Cytoplasmic streaming – amoeboid
movement
- Tips of pseudopods are less viscous so
flow goes in that direction
- Pseudopods for phagocytosis
- Reproduce by binary fission
i.e. Amoeba, Naegleria, Heliozoans, Radiolarians,
Foraminifera
• Sporozoa
– No method of motility
– All are parasites – use host for motility
– Reproduce by schizogamy (multiple fission) in
host & sexual reproduction in a second host
Ie. Plasmodium (malaria), Giardia, Toxoplasma,
Trypanosoma, Trichomonas
Animal-Like Protists
PROTOZOAN PROTIST
EVOLUTION
•Evolved from the Archae approx. 1.5 billion years ago
•Polyphyletic group- protists arose by way of more than
one ancestral group
•Represents separate evolutionary lineages
•Plant like b/c autotrophic (produce their own food)
•Animal-Like b/c they are heterotrophic (feed upon other
organisms)
Figure 8.20
TYPES OF PROTOZOANS
• Zooflagellated Protozoans
• Flagellated Protozoans
• Phytoflagellated Protozoans
Zooflagellated Protozoa
• Lack chloroplast
• Heterotrophic
• Some members are important human
parasites
• Species Trypanosoma brucei cause African
sleeping sickness (Intermediate host- Tsetse
flies )
Figure 8.8 (b)
Flagellated Protozoa
• Flagellates are the ancestors of ameoboid
protozoan
• Phytoflagellated (photosynthesizing)
• Zooflagellated (particle feeding and
parasitic)
pellicle
contractile
vacuole
macronucleus
cytoplasm:
ectoplasm
endoplasm
micronucleus
cilia
oral groove
anal pore
gullet
food
vacuole
Phytoflagellated Protozoa
• Chlorophyll (oxygen for marine life)
• One or two flagella
• These protozoans are large portion of the
marine food i.e dinoflagellates
• Two flagellates, chlorophyll, xanthophyll
(bloom=red tides) and results in fill kills (Red
sea, bible)
Figure 8.6
Other Phytoflagellated Protozoa
Euglena
• Freshwater
phytoflagellated protozoa
• Chloroplast has a pyrenoid
(synthesizes and stores carbohydrates)
• Feed by absorption or are
heterotrophic
• Stigma- photoreceptor at the base of
the flagellum
• Haploid organisms and reproduce
binary fission
FUNGUS LIKE PROTISTS
• Like fungi, they are heterotrophs, have cell walls, use spores to reproduce.
Unlike fungi, they can move at some points in their life cycle.
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Three types:
- Water Molds and Downy Mildews:
Both types live in water or moist places, & look like
fuzzy threads.
They attack food crops (potatoes)
- Slime Moulds:
Live in moist soil and on decaying plants and trees.
Some are with beautiful colors. They move using
pseudopods.
They eat bacteria and other microorganisms.
Can combine, forming a multicellular mass & spores.
Spores develop into a new generations of slime moulds
PLANT LIKE PROTISTS
Called algae & are autotrophs (pigments & photosynthesis).
* Some are unicellular, living unconnected from other algae cells.
* Others form colonies together with a few cells specializing for
reproduction, etc. (Most colony cells continue to carry out all
normal functions.)
* Some algae are multicellular like seaweed, where all cells are
specialized.
Paramecium Movement
• The outer surface of the cell is covered
with many hundreds of tiny hair-like
structures called cilia.
• These act like microscopic oars to push
through the water, enabling the
organism to swim.
• If Paramecium comes across an
obstacle, it stops, reverses the beating
of the cilia, swims backwards, turns
through an angle and moves forward
again on a slightly different course.
• It moves so quickly that we have to add
a thickening agent or quieting solution
to the slide to slow it down to study it.
Paramecium Feeding
• Paramecium has a permanent feeding
mechanism, consisting of an oral groove and a
funnel-shaped gullet into which food is drawn by
the combined action of cilia which cover the
body and other cilia lining the oral groove and
the gullet.
• As it moves through the water it rotates on its
axis and small particles of debris and food are
collected and swept into the gullet.
• They feed on small organisms such as bacteria,
yeasts, algae and even other smaller protozoa.
Paramecium Excretion
• Food waste left in a food
vacuole is excreted through
the anal pore (the vacuole
and pore fuse.
• Other wastes left over from
cellular activity (metabolic
waste) simply diffuse through
the pellicle.
• Excess water and some
metabolic wastes are
excreted through the
contractile vacuole.
ASEXUAL REPRODUCTION IN
PROTOZOANS
Asexual Reproduction in Protozoa
Conjugation in Paramecium
Paramecium Reproduction
• In favourable conditions the
cell divides in two by a process
called binary fission (asexual
reproduction).
• This forms two new cells, each
of which rapidly grows any
new structures required and
increases in size.
• This whole process may take
place two or three times a day
if conditions were right.
Paramecium Reproduction
• This is a more complicated
method called conjugation
(sexual reproduction).
• It involves two cells coming
together to exchange nuclear
material.
• The two cells then separate
and continue to reproduce by
simple division.
• It is similar in some ways to
sexual reproduction in more
complex animals.
Reproduction in Ciliates
Paramecium
conjugating
Transverse Binary
fission
Symbiotic lifestyles
• Symbiosis
• Parasitism- a form of symbiosis- organism
lives in or on other (Host)
Other kinds of symbiosis
• Don’t harm host
– Commensalisms- one member benefits
– Mutualism- both benefit
Some parasites have life cycles involving
multiple hosts
• Definite host- harbors the sexual stages of
the parasite
• Intermediate host- the offspring enter
another host where they reproduce asexually,
to complete lifecycle the final asexual stage
must have access to a Definite host
Paramecium Grammers
• Growth: 0.05 mm avg.
• Respond:
-react to chemicals – salt and vinegar
-live in slightly acidic environments (stagnant
H2O)
-anterior end sensitive – move by trial and
error
Paramecium continued…
• Adaptations:
– Cilia to help feed and escape
– Contractile vacuoles
– Trichocysts
Paramecium continued…
• Movement: by cilia in circular motion, move ~ 60
mm/hr
• Metabolism:
-food pulled into oral groove by cilia
-food vacuole forms at gullet
-lysosome aids with digestion
• Feed mostly on bacteria, smaller protozoans and
algae.
Paramecium continued…
• Excretion:
-Contractile vacuole removes excess H20.
-C02 across pellicle by diffusion
-anal pore removes waste.
• Reproduction: Asexual - cell division
Sexual – conjugation (exchange
of micronucleus DNA)
CLADOGRAM OF PROTOZOA
RELATIONSHIPS
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Endosymbiosis and Cytoplasmic
Inheritance in Paramecium
This Topic Will Focus On The Following :
Altenburg paper (1948)
–Plasmagene hypothesis
–Kappa body symbiosis
Other cytoplasmic inheritance
in Paramecium (Meyer 2002)
Current understanding
of Kappa bodies (Preer
1974)
Paramecium biology
–Cell biology
–Life cycle
Altenburg paper (1948) investigates the evidence that
Kappa bodies are a symbiont
Kappa bodies are elements within Paramecium that cause
them to be killers
Killer Paramecium kill other Paramecium in the
immediate environment
Kappa particles, thought to be plasmagenes by Sonneborn, but Altenburg
suggest they may be symbionts
The plasmagene theory suggested kappa bodies were
genes within the cytoplasm
Plasmagenes defined as self-replicating structure capable of
producing traits that exist in the cytoplasm and are independent of
chromosomal genes.
The trait that Kappa bodies produce is the killing factor
Kappa bodies are inherited through the cytoplasm and not through
chromosomes
Sonneborn wrote in 1976, “It was awful of me to be so attached to a pet
idea. That was an ordeal between my mind and my heart and it took a
while for the mind to win and the heart to accept. Impersonal scientific
objectivity is a goal to be sought by hard self-discipline; we are not born
with it.”
Altenburg’s evidence that Kappa bodies are symbionts is
strongly supported by evidence
Preer (1948) showed Kappa is large enough to see under a
light microscope
38o C kills Kappa but not Paramecium
Division of Kappa and Paramecium is independent of each
other
Paramecium with symbiont
There is an upper limit of the number of Kappa in Paramecium
More likely a symbiont than a parasite
Preer (1974) reviewed the overwhelming evidence that
Kappa bodies are symbionts
Kappa contains DNA, RNA, protein, and lipids in
proportions expected in bacteria
Kappa contains electron transport system with
cytochromes similar to bacteria and not eukaryotes
Electron micrograph of symbionts
Electron microscopy clearly showed that Kappa is
prokaryotic
Electron micrograph of flagellated Kappa
Current information has shown why Kappa induces killing
and the different types of bacteria symbiosis
Kappa bodies kill other Paramecium by releasing toxins into the
environment
The presence of the symbiont makes the host resistant to the toxin
Kappa bodies are transmitted by the cytoplasm during asexual division
Many other types of symbionts found
gamma
sigma
lambda
Kappa is the most common
alpha
delta
pi
omega
mu
The discovery of bacterial symbionts within Paramecium
allows for their taxonomic classification
Kappa, mu, gamma, and nu are in genera Caedobacter
Alpha bodies are in the genera Cytophaga
Lambda and sigma are in genera Lyticum
Delta bodies are in genera Tectobacter
Differences have been found between Kappa bodies in the
same host
Some Kappa bodies contain refractile ( R ) bodies
R body is a type of inclusion body
When genes from one organism are within
another organism and are transcribed, a
inactive protein may form
Magnified image of coiled R body (2)
Kappa bodies may contain ‘R’ bodies and it affects their
reproductive capability
Non bright Kappa bodies do not contain R bodies but can
reproduce
Bright Kappa bodies do contain R bodies but cannot
reproduce
Dividing symbiont
Non bright produce other non bright, but occasionally a non
bright turns into a bright
Toxicity associated only with Brights
There is still unsolved questions regarding Kappa body
symbiosis
What benefit does Paramecium get from the
symbiosis?
How does the presence of a Kappa body induce resistance to the
toxin?
Resistance can be overcome with large toxin dose
The presence of Kappa with or without R bodies
induces resistance to the toxin
Other types of cytoplasmic inheritance discovered in Paramecium and
other ciliates is:
Genome-wide DNA rearrangements
Mating type
Serotypes
Paramecium has a complex cellular biology
Eukaryotic
Ciliates contain at least 2 nuclei
Germ-line micronucleus (MIC)
Somatic macronucleus (MAC)
MAC is generated from the MIC
Diagram of Paramecium
Extensive genome rearrangements occur in the MAC
The two nuclei make the life cycle of Paramecium more
complicated than other eukaryotes
MIC goes through meiosis and the haploid
MIC goes through mitosis
Result is 4 haploid MIC, but 2 are
degraded
Paramecium exchange 1 haploid MIC
MIC fuse and form diploid MIC and
duplicate via mitosis
Old MAC degrades and duplicated MIC
is processed into new MAC
In asexual reproduction, the MIC goes
through mitosis and the MAC goes through
amitosis
Genome-wide rearrangements of the MAC genome
consists of deletion of DNA sequences and chromosome
amplification
The developing new MAC loses 10 - 95% of
the genome depending on the ciliate
MAC chromosomes are amplified to a high
ploidy level
Deletion occurs after an initial amplification
of the MIC genome but before the ploidy
level is reached
The deletion of DNA is located at specific sequences called
internal excised sequences (IES)
IES are located in coding and non-coding regions of the MIC genome
These sequences are not present in the MAC genome
At some point in MAC development, the IES sequences are deleted
The mating type of Paramecium
shows maternal inheritance
Conjugation of P. caudatum by Yanagi
Paramecium has 2 mating types - O and E
Both are not determined by genetic differences as they are both produced
in homozygous wild-type strains
Mating type is the same through asexual reproduction but can change after
sexual conjugation and MAC formation
After conjugation O cells mostly produce other O cells and E cells produce
other E cells
Paramecium mating types do not follow the
Mendelian segregation of alleles
A.
B.
Mendelian segregation of allelic pairs
Maternal inheritance of mating types
Mating types O and E depends on different states
of MAC genome
Transferring E maternal MAC into O cell causes the progeny to become E
Transferring O MAC does not change E cells
O is the default mating type
O cell
E cell
E cell
Produces
Insert E MAC
This differential state of MAC is dependent on the
presence of IES in the MAC
The mutation mTFE causes O cells to become E
This mutation affects the excision of an IES on the G gene
The G gene is a surface antigen and the failure of
excision causes a nonfunctional protein to be
translated
Functional - type O
excision
MIC G gene
Mutational
retention
Nonfunctional - type E
MAC G gene
Microinjection studies have shown that the presence of
an IES sequence in the MAC inhibits the excision of its
homologous IES in the MIC
O cells contain G gene in the MAC without its IES (IES-)
E cells contain the G gene in the MAC with its IES (IES+)
Injecting a plasmid of IES+ G gene into O cell’s MAC created the retention of the
IES in the MAC of daughter cells
Injection of IES- plasmid did not induce excision
The presence of IES in the MAC causes the retention of the IES in subsequent
generations after sexual conjugation
Microinjection of IES+ plasmid retains the IES in the
MAC genome after autogamy
Meyer (2002) asked, “How can a sequence introduced in one
nucleus affect the excision of the homologous sequence in another
nucleus?”
Two models developed
Model 1: Sequence-specific protein factors are required for
the excision of the IES in the developing MAC
The problem with this model is the large
number of protein factors needed, about
50,000
Model 2: Sequence specificity is achieved by homologous nucleic acid (most likely
RNA) that is transported from the maternal MAC to the developing MAC
Mochizuki (2004) explained the Scanning Model, a synthesis
of Meyer’s model 1 and 2
Entire MIC genome is transcribed bidirectionally and forms dsRNA
dsRNA is cut up into smaller RNA
called scn RNA
Scn RNA move to the old MAC and any
matching homologous sequences are
degraded
Scn RNA that were not degraded move to
the developing MAC
These scn RNAs target homologous
sequences which are deleted in an RNA
i-like mechanism
Polymorphic lifestyles
• Have different forms during their life cycle
• May form cysts (vegetative cells) when
adverse conditions exist. Cysts are not heat
and chemically resistant.
SUMMARY
Paramecium has many instances of cytoplasmic and maternal
inheritance
Paramecium
Kappa bodies are bacterial symbionts that produce a killing
factor and they are inherited through the cytoplasm
IES excision and retention in the MAC is maternally inherited by
the genome present in the MAC
Electron micrograph of Kappa
Ecological importance
• Members of the food chain – Primary or
Secondary consumers
• Consume soil bacteria & algae (1 paramecium
can ingest 5 million bacteria/day
• Involved in sewage disposal by metabolizing
nutrients present to carbon dioxide & water
HARMS
• Cause disease in host organisms
Malaria – Plasmodium via mosquito
Toxoplasmosis – Toxoplasma
African Sleeping Sickness – Trypanosoma
via tsetse fly
Chagas – Toxoplasma
Vaginitis – Trichomonas
Giardiasis – Giardia
150 million people/year in world contract Malaria &
1.5 mill/year die of it.
FACTS ABOUT PARAMECIUM
“One scientist calculated that if all the
progeny of a single Paramecium
survived, assuming a division rate of
once a day, then after 113 days, the
mass of paramecia would equal the
volume of the Earth! “