L19 - Protists Flashcards
What are the protists?
Unicellular eukaryotes but also multicellular prokaryotes. Have varied sizes and morphologies. Have great phylogenetic diversity. Abundant in aquatic ecosystems
Classification of protists
Motile they are free-living and need motility to access food and avoid predation. Non-motile parasites of animals.
Classifications are dynamic
Protista are not a formal taxon but Protist is still used as a term.
What are multicellular protists - seaweeds?
Chloroplastida (green algae)
Rhodophyta (red algae)
Phaeophyta (brown algae)
Multicellular protists brown algae
Brown algae (phaeophyta) including kelps are multicellular protists. Kelps contain different photosynthetic pigments than plants such as chlorophyll C and fucoxanthin
Multicellular protists red algae
Rhodophyta have chlorophyll a and reddish pigment phycobilins
Unicellular photosynthetic protists within the phytoplankton
Coccolithophores, diatoms, dinoflagellates
What are coccolithophores?
Use CO2 for photosynthesis and to make chalky (CaCO3) shells. These organisms can sequester atmospheric CO2. As they grow bigger and/or divide they shed the coccoliths which sink in the ocean.
What do coccolithopores produce and how?
They produce massive bloom that cover vast surfaces of the ocean. These blooms are highly reflective and cause light and heat to be reflected into space making earth brighter. CaCO3 shells are highly reflective when large quantities are present they create colourful patterns
How do coccolithopores contribute to cloud formation?
They produce DMSP, which contributes to cloud formation : site of nucleation of a raindrop. Dimethylsulfoniopropionate (DMSP) converted dimethylsulfide (DMS) which is converted to sulphate in the atmosphere. Sulphate acts as a nucleation agent for water vapour to become water droplets, clouds are formed.
What are diatoms?
Photosynthetic, abundant in marine and freshwater environments. Important food source for marine organisms. Cell wall made of silicon dioxide which is very tough and resistant to mechanical breakthrough.
What does the diatoms shell consist of?
Two unequal parts. During replication each part serves as a template for a new shell.
What is Diatoms replication process?
During asexual reproduction top shell of the cell serves as a template for the bottom. New bottom becomes a top and acts as a template for another bottom. New new bottom becomes a top, and another bottom is made ; with each division the shell becomes smaller and smaller. When the shell is too small, the cell exits the shell undergoes meiosis and forms gametes. The gametes can fuse to form a zygote, which can grow a new shell.
What is Diatoms replication process?
During asexual reproduction top shell of the cell serves as a template for the bottom. New bottom becomes a top and acts as a template for another bottom. New new bottom becomes a top, and another bottom is made ; with each division the shell becomes smaller and smaller. When the shell is too small, the cell exits the shell undergoes meiosis and forms gametes. The gametes can fuse to form a zygote, which can grow a new shell.
What are dinoflagellates?
Protists with a shell made of cellulose or other organic polymers, some of them are photosynthetic and others are heterotrophs. Most are marine but some are freshwater.
What do some dinoflagellates produce?
Photosynthetic red pigments, produce neurotoxins which contaminate seafood. Some are bioluminescent.
What are non-photosynthetic unicellular protists?
Predators, pathogens and parasites. Some protists are predatory and feed on other microbes
Protists and Cyanobacteria
Protists preying on bacteria is the major cause of death among prokaryotes. Protists feeding on Cyanobacteria prevent Cyanobacteria blooms. Cyanobacteria blooms can release toxins in water and deplete aquatic environments of oxygen.
What is a useful role of protists?
Purification of wastewater, team up with aerobic bacteria in aeration tanks to degrade the organic matter. When nutrients are gone, protists eat the bacteria.
Pathogenic behaviour in protists
Parasites/pathogens plants and fish, as fungal like heterotrophs they have branching tip-growing mycelia, unlike fungi they have cellulose and only a little chitin in their cell wall.
Unique cell structures of the protists
Most protists have eukaryotic cell organisation. Some of these structures can have unusual forms some protists carry more than one nucleus, some protists do not have true mitochondria.
What are protists with more than one nucleus called?
Paramercia have two nuclei both contain a full complement of genes. Macronucleus is ellipsoid in shape and contains multiple copies of a subset of genes required for growth. Micronucleus is essential for reproduction as the storage site for the germline material. Micronucleus contains 2 copies of all the genes. Two nuclei means paramecia divide faster. Multiple copies of the same gene within the macronucleus mean genes transcribed faster and proteins made faster.
Protist with more than one nucleus example? And how does it reproduce?
Plasmodium, malarial parasite which can reproduce asexually by schizogony. Schizogony process where cell size increases and the nucleus and other organelles divide repeatedly. Forming a cell called a schizont. Eventually ruptures releasing tiny cells.
What anaerobic protists do not have mitochondria?
Mitosomes which do not produce ATP. Hydrogenosomes produce ATP via reactions that generate hydrogen as a by-product. Both their membrane-bound organelles do not contain DNA unlike mitochondria
What are examples of non-photosynthetic protists?
Paramecia (ciliates), Plasmodium (acicomplexa), labyrinthulomycetes
What are paramecia?
Use short appendages (cilia) to move around. Inhabit pond water, rivers, lakes, oceans and soils. Paramecia are predators but also prey, they are an excellent food source for larval fish.
What do paramecia eat? How do they eat it?
Organic particles, bacteria, yeasts and other protists. They move via cilia and drag nutrients towards it, including other microbes. Food is swept by the cilia directly into the gullet. Where it is digested in the food vacuole, nutrients are released into the cytoplasm, undigested food material is excreted through the anal pore.
What role does paramecia and bacteria symbiosis play?
Paramecia swallow any particles they find in their path, including bacteria. Some bacteria produce toxins deadly to paramecia. Some paramecia have developed resistance to bacterial toxins and ingest and carry the killer bacteria. Bacteria find shelter inside the paramecium and the paramecium becomes toxic to predators.
What role does paramecia and algae symbiosis play?
Paramecium and algae come together when nutrients are scarce, algae give the paramecia nutrients from photosynthesis. Paramecia protect the algae and use their cilia to reach the surface where light and CO2 are more abundant.
What is plasmodium?
Causative agent of malaria, human malaria affects 300 million people in tropical areas. There are 5 species of plasmodium and that cause human malaria. Plasmodium alternates between two obligatory life stages, one in the mosquito and the vertebrate host.
How do mosquitoes acquire plasmodium?
Only female mosquitoes need blood, if a female mosquito feeds on a host infected with malaria, the mosquito acquires the parasite. Ingested blood contains plasmodium parasites in various stages. Only when plasmodium cells differentiate into gametophytes can they infect the insect.
What is the mosquito life cycle?
In the mosquito’s gut the gametes exit the red blood cells, male gametes seek out female gametes. Within 30minutes of entering the mosquito, mating is completed, and diploid zygotes are formed. Zygotes invade the mosquito gut. During this process of meiosis takes place. The zygote differentiates into haploid cells that are released into the mosquito hemolymph. Oocutes develop into sporozoites and travel to the mosquitoes salivary glands, where they can be transmitted in the next blood meal.
How does plasmodium get into the vertebrate host?
In humans sporozoites travel to the liver, plasmodium can either multiply in the liver or can remain dormant. Sporozoites mature into schizonts, these schizonts penetrate the red blood cells. RBC are not phagocytic and do not have lysosomes therefore plasmodium cannot be digested
What is the life cycle inside the vertebrate host of plasmodium?
In RBCs, the parasite matures into rung shaped-forms. Infected RBCs become stiff. Parasites induce the formation of knob-like structures on the RBCs to make infected RBCs adhere to the blood vessels or other RBCs. This avoids them being destroyed by the spleen. Fully mature parasites are released, losing the infected RBCs resulting in other RBCs being infected.
What symptoms of malaria does lysis of RBCs coincide with?
Chills, weakness, headaches, vomiting, high fever.
What are labyrinthulomycetes?
Largely aquatic microorganism that produce a network of filaments or tubes which serve as tracks for the cells to glide along and absorb nutrients for them
What are the two main groups of labyrinthulomycetes?
Labyrinthulids which grow as networks of branched slime tubes containing motile cells. Thraustochytrids which grow as zoospore-producing thalli.
What do labyrinthulomycetes have?
Vegetative cells of eelgrass labyrinthula. The ectoplasmic net can be seen as thin white extensions. Thraustochyrid cells with ectoplasmic threads undergoing binary division. Ectoplasmic threads are extensions of plasma membrane
Example of labyrinthula
Causative agent of wasting disease. Wasting disease led to death of >90% of the seagrass pop. L. zosterae attacks and consumes plant chloroplasts, reduces photosynthesis, creates large areas of necrotic tissue.
What is the importance of seagrass?
Only marine angiosperm, carbon sequester occupy 0.1% of sea floor but responsible for 11% of organic carbon buried. Basis of the world’s primary fishing grounds. Prevents coastal erosion including stabilising sediment in the ocean.
Labyrinthula terrestris
Only know land-based Labyrinthula, requires a rise in salt to establish.
