L19 - Protists

Question 1

What are the protists?

Answer 1

Unicellular eukaryotes but also multicellular prokaryotes. Have varied sizes and morphologies. Have great phylogenetic diversity. Abundant in aquatic ecosystems

Question 2

Classification of protists

Answer 2

Motile they are free-living and need motility to access food and avoid predation. Non-motile parasites of animals.

Question 3

Classifications are dynamic

Answer 3

Protista are not a formal taxon but Protist is still used as a term.

Question 4

What are multicellular protists - seaweeds?

Answer 4

Chloroplastida (green algae)
Rhodophyta (red algae)
Phaeophyta (brown algae)

Question 5

Multicellular protists brown algae

Answer 5

Brown algae (phaeophyta) including kelps are multicellular protists. Kelps contain different photosynthetic pigments than plants such as chlorophyll C and fucoxanthin

Question 6

Multicellular protists red algae

Answer 6

Rhodophyta have chlorophyll a and reddish pigment phycobilins

Question 7

Unicellular photosynthetic protists within the phytoplankton

Answer 7

Coccolithophores, diatoms, dinoflagellates

Question 8

What are coccolithophores?

Answer 8

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.

Question 9

What do coccolithopores produce and how?

Answer 9

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

Question 10

How do coccolithopores contribute to cloud formation?

Answer 10

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.

Question 11

What are diatoms?

Answer 11

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.

Question 12

What does the diatoms shell consist of?

Answer 12

Two unequal parts. During replication each part serves as a template for a new shell.

Question 13

What is Diatoms replication process?

Answer 13

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.

Question 14

What is Diatoms replication process?

Answer 14

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.

Question 15

What are dinoflagellates?

Answer 15

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.

Question 16

What do some dinoflagellates produce?

Answer 16

Photosynthetic red pigments, produce neurotoxins which contaminate seafood. Some are bioluminescent.

Question 17

What are non-photosynthetic unicellular protists?

Answer 17

Predators, pathogens and parasites. Some protists are predatory and feed on other microbes

Question 18

Protists and Cyanobacteria

Answer 18

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.

Question 19

What is a useful role of protists?

Answer 19

Purification of wastewater, team up with aerobic bacteria in aeration tanks to degrade the organic matter. When nutrients are gone, protists eat the bacteria.

Question 20

Pathogenic behaviour in protists

Answer 20

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.

Question 21

Unique cell structures of the protists

Answer 21

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.

Question 22

What are protists with more than one nucleus called?

Answer 22

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.

Question 23

Protist with more than one nucleus example? And how does it reproduce?

Answer 23

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.

Question 24

What anaerobic protists do not have mitochondria?

Answer 24

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

Question 25

What are examples of non-photosynthetic protists?

Answer 25

Paramecia (ciliates), Plasmodium (acicomplexa), labyrinthulomycetes

Question 26

What are paramecia?

Answer 26

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.

Question 27

What do paramecia eat? How do they eat it?

Answer 27

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.

Question 28

What role does paramecia and bacteria symbiosis play?

Answer 28

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.

Question 29

What role does paramecia and algae symbiosis play?

Answer 29

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.

Question 30

What is plasmodium?

Answer 30

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.

Question 31

How do mosquitoes acquire plasmodium?

Answer 31

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.

Question 32

What is the mosquito life cycle?

Answer 32

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.

Question 33

How does plasmodium get into the vertebrate host?

Answer 33

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

Question 34

What is the life cycle inside the vertebrate host of plasmodium?

Answer 34

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.

Question 35

What symptoms of malaria does lysis of RBCs coincide with?

Answer 35

Chills, weakness, headaches, vomiting, high fever.

Question 36

What are labyrinthulomycetes?

Answer 36

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

Question 37

What are the two main groups of labyrinthulomycetes?

Answer 37

Labyrinthulids which grow as networks of branched slime tubes containing motile cells. Thraustochytrids which grow as zoospore-producing thalli.

Question 38

What do labyrinthulomycetes have?

Answer 38

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

Question 39

Example of labyrinthula

Answer 39

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.

Question 40

What is the importance of seagrass?

Answer 40

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.

Question 41

Labyrinthula terrestris

Answer 41

Only know land-based Labyrinthula, requires a rise in salt to establish.