Eukaryotic supergroups Flashcards

Question

What is Eimeria? | - why is it important to know about it and understand it?

Answer 1

Eimeria • Apicomplexan parasite (SAR) • Affects almost all vertebrates eg. cattle, poultry, fish • As few as 50,000 infective oocysts can cause severe disease in a young calf Impacts on global food security, act as reservoirs for human infection, harm animal welfare

Answer 2

* SAR, Alevolata * Phylum of obligate parasitic protozoa, eg. T. gondii, Plasmodium, Eimeria • Contain a unique form of organelle called an apicoplast - Apicoplast is a degenerate chloroplast, and is no longer capable of photosynthesis - Results from secondary endosymbiosis of cyanobacteria * No flagella or cilia - they use a unique form of actin-based gliding motility to target and invade host cells * Food taken up in soluble form across the cytoplasmic membrane * Sexual & asexual reproduction * Produce sporozoites (spore-like bodies) which function into transmission to new host * Named after the apical complex (collection of organelles involved in attachment and invasion of host cells)

Answer 3

Toxoplasma gondii • Obligate intracellular single celled parasite, apicomplexan!! • Causes infectious disease toxoplasmosis Definitive host - Felids (eg. domestic cats) are the only definitive hosts Intermediate hosts - can be many warm blooded species (including humans) Can cause significant damage to foetuses in pregnant women

Answer 4

• Euk pathogens can have complex lifecycles with both sexual and asexual phases • Capacity to produce resting stages - For example, very resistant spores • Euk.s separate growth from reproduction → They can have much larger genomes → More elaborate systems → Life cycle can accommodate multiple hosts • Diverse means of locomotion & spread • Transmission routes: - Faecal-oral eg. T. gondii, Eimeria - Sexual - Vectors (mostly insects) eg. Plasmodium • High mortality of offspring result in strategies to produce lots of them

Answer 5

Life cycle stages 1. Sporozoite ❖ Motile, spore-like stage ❖ Develop into trophozoites 2. Trophozoite ❖ Intracellular feeding stage before schizogony 3. Merozoite ❖ Develop from asexual reproduction within the schizont ❖ Released and develop into male/female gametes

Answer 6

- Eimeria - Toxoplasma gondii - Giardia intestinalis

Answer 7

• Challenges: - Need to resist the environment (cysts or oocysts) - High parasite losses so need high no.s - Need a way of sensing entry into host - Host availability can be problematic

Answer 8

• Advantages + adaptation focussed on single host type + ease of entry into the host by ingestion (bypass barriers like skin) + can remain metabolically inactive in environment (increases survival chances)

Answer 9

They invade in v different ways - secreting proteins - using attachment discs - gliding motility aiding attachment

Answer 10

resistant to conventional water treatment methods such as chlorination

Answer 11

Giardia intestinalis * Causes giardiasis, which can range from asymptomatic to severe diarrhoea and vomiting * Infection can occur through ingestion of cysts in contaminate water or food or by the faecal-oral route * Reproduce in the SMALL INTESTINES of several vertebrates, causing giardiasis * Trophozoites swim through intestinal mucus, then use an adhesive disc to attach to the host intestinal epithelium * Remains confined to the lumen of the small intestine, where trophozoites absorb their nutrients and then undergo ASEXUAL REPRODUCTION by binary fission * Then produce cysts which are expelled in faeces G. intestinalis are flagellated, have two nuclei of equal size, and contain mitosomes instead of mitochondria (not used in ATP synthesis like mitochondria, but instead are involved in the maturation of iron-sulfur proteins)

Answer 12

- Plasmodium spp. (mosquitos, malaria) - Trypanosoma brucei (Tsetse flies, sleeping sickness) - Leishmania spp. (Sandflies, leishmaniasis)

Answer 13

- Needs to adapt to multiple hosts (and their differing immune responses) - Needs a way of transferring between hosts - Needs a way of sensing change of host to change strategies - Host availability/lifespan can be problematic

Answer 14

+ invertebrate host provides protection from the environment + ease of entry by injection into a wound (use insect biting parts to get into wound – host manipulation!!) + vector-based dispersal (malaria has wings!) + vector-based host selection

Answer 15

1. Mosquito injects sporozoites into bloodstream when it bites human 2. Sporozoites travel to liver and take residence in hepatocytes 3. Sporozoites multiply asexually into schizont, which ruptures, releasing merozoites back into the bloodstream 4. Merozoites invade erythrocytes, forming ring-like trophozoite. 5. The ring stage trophozoites multiplies asexually to form schizonts, which rupture releasing merozoites when rbcs burst 6. This cycle of rbc invasion, multiplying and bursting continues, causing malarial symptoms such as chills and sweating 7. After several asexual cycles, the merozoites will form gametocytes when it infects a rbc 8. Gametocytes sucked up by another mosquito, digesting the gametocytes and allowing them to mature into gametes, which fuse together to form oocyte 9. Oocyst develops sporozoites which are released when oocyst ruptures 10. Sporozoites migrate to mosquito’s salivary glands

Answer 16

fevers and chills, headache, vomiting, neurological symptoms

Answer 17

SLEEPING SICKNESS * Free-living (extracellular) parasite carried around in bloodstream of infected hosts * One of the few pathogens to cross the blood brain barrier * Carried by Tsetse fly vector between mammal hosts * Flagellated (9+2) * Has an unusual organelle called a kinetoplast made up of many copies of the mitochondrial DNA * Have glycosomes (membrane bound organelles containing the glycolytic enzymes) which are derived from peroxisomes How do they reproduce? • In mammal BLOOD & and LYMPH, grow long and thin and multiply by binary fission, penetrate blood vessel endothelium and invade tissue including CNS • In fly, multiply and enter salivary glands

Answer 18

Trypanosoma • Have surface glycoprotein – express VSG (variant surface glycoproteins) • Able to make new VSGs from library of genes they have – great way of achieving promiscuity

Answer 19

Symptoms: - Haemo-lymphatic stage causes fever, headaches, joint pain - Neurological stage when parasite infects CNS - Changes of behaviour, confusion, poor coordination - Usually fatal without treatment

Answer 20

• Parasites remain significant causes of morbidity and mortality – Impact especially great in low income countries. • Parasite biology enables complex lifestyles and relationships with, sometimes multiple, hosts – Widespread occurrence of dormant resistant forms; – Some organisms have evolved mechanisms of immune evasion. • Public health interventions are often complicated and expensive (no vaccines!).