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BIOC1010 Dina > eukaryotic microbes > Flashcards

eukaryotic microbes Flashcards

1
Q

explain the main features of protozoa

A
  • single-celled
  • lack a rigid cell wall
  • usually motile
  • inhabit a ‘wet’ environment
  • may form a resting stage comprising of spores or cysts
  • heterotrophs
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2
Q

explain the main features of algae

A
  • essentially protozoa with a plastid

- organisms in which the plastid is a chloroplast are phototrophs

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3
Q

what does Leishmania cause?

A

leishmaniasis

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4
Q

what does Phytophthora infestans cause?

A

potato blight

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5
Q

what does Phytophthora palmivora cause?

A

blight of cocoa pods

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6
Q

what do dinoflagellates cause?

A

red tides

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7
Q

which organism gave rise to the white cliffs of Dover and how?

A

Emiliana huxylei

CO2 —> CaCO3 + C6H12O6

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8
Q

how have eukaryotes evolved from prokaryotic Archaea?

A
  • internal membrane formation
  • cell enlargement
  • serial endosymbiosis
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9
Q

give examples of prokaryotes that have eukaryotic features

A

Gemmata obscuriglobus has a nuclear envelope

cyanobacteria have thylakoid membranes

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10
Q

which organisms were the precursors of eukaryotes?

A

protoeukaryote, early α-proteobacterium, early cyanobacterium

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11
Q

what is the distinctive feature of a protoeukaryote?

A

genetic information surrounded by endomembrane (rudimentary nucleus)

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12
Q

which organism gave rise to the mitochondrion?

A

early α-proteobacterium

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13
Q

which organism gave rise to the chloroplast?

A

early cyanobacterium

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14
Q

what are the four major groups of protozoa?

A
  1. alveolates
  2. euglenoids
  3. oomycetes
  4. sarcodina
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15
Q

what are alveolates?

A

protozoa that possess alveoli (sac-like membrane structures filled with fluid that lie beneath the cell membrane

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16
Q

what are the main phyla of alveolates?

A

i. ciliates
ii. sporozoans
iii. dinoflagellates

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17
Q

what are euglenoids?

A

flagellated protozoa

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18
Q

give some examples of euglenoids

A

i. Euglena
ii. Trypanosomes
iii. Leishmania

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19
Q

what are oomycetes?

A
  • ‘water moulds’
  • filamentous protozoa
  • either free-living or parasitic
  • may grow as ‘fungal-like’ hyphae
20
Q

give some examples of oomycetes

A

i. Phythophthora infestans
ii. Plasmopara viticola
iii. Saprolegnia species

21
Q

what are sarcodina?

A
  • largest phylum of protozoa

- most are free-living

22
Q

describe the main features of ciliates

A
  • found almost everywhere there is water
  • cell surface covered in cilia that beat to propel the ciliate forwards through water and/or draw in food particles
  • free-living ciliates feed mainly on bacteria,algae and other ciliates (Didinium)
  • some ciliates harbour symbiotic algae
23
Q

give examples of ciliates

A

Paramecium - feeds mainly on bacteria; reproduces asexually or sexually by conjugation
also Vorticella, Stentor

24
Q

describe the main features of sporozoans

A
  • haploid parasitic protozoa
  • complex lifestyle involving growth stage within host cell
  • major sub-group is apicomplexans
25
Q

what are apicomplexans?

A

distinctive structure at apical end of sporozoite ( involved in host cell invasion)
eg. Plasmodium, Toxoplasma, Elmeria

26
Q

to which group to cilia and sporozoans belong?

A

alveolates

27
Q

describe the main features of Euglena

A
  • many possess chloroplasts
  • but also capable of heterotrophic growth
  • in some species, chloroplast is easily lost (‘bleaching’)
28
Q

describe the main features of Tryposomes

A
  • flagellated pathogens of animals and plants
  • life cycle involving an insect host
  • possess a kinetoplast
    eg. Tryposomona brucei - sleeping sickness
29
Q

what is a kinetoplast?

A

a specialised DNA-containing structure in mitochondrion

30
Q

give examples of oomycetes

A
  • Phytophthora infestans - causes potato/tomato blight
  • Plasmopare vitizola - causes grape mildew
  • Saprolegnia species - grow on the scales of fish; cause lesions when fish are in high density
31
Q

give an example of a sarcodina

A

Dictystelium discoideum (Dicty)

32
Q

describe the main features of Dictystelium discoideum

A
  • haploid unicellular amoeba
  • feeds on bacteria in soil
  • divides by mitosis (or has a sexual life cycle involving mating types)
  • when food becomes scarce, cells undergo a developmental change to create a multicellular organism (‘slug’)
  • cells secrete cAMP to attract other cells, which adhere via glycoproteins on the cell surface
  • slug differentiates into a fruiting body, which releases spores when mature
  • some Dicty display ‘husbandry’; they store cells of bacterial prey as symbionts to take with them to their new niche
33
Q

how long is a slug?

A

2-4 mm

34
Q

describe the main features of Entamoeba histolytica

A
  • major human pathogen
  • two stages in life cycle: 1) motile amoba (trophozoite); 2) cyst
  • ingested cysts are resistant to stomach acid and hatch to form amoebae in the colon
  • new cysts form and pass through the bowel
  • normally no symptoms
  • but some individual amoebae become invasive and attack organs, resulting in localised infection (amoebic dysentry) or systemic infection of many organs, including the brain
35
Q

describe the main features of Entamoeba gingivalis

A
  • related to Entamoeba histolytica
  • lives between teeth and is associated with periodontal disease and gingivitis
  • doesn’t form cysts
  • infects only the mouth
  • passed on by kissing
36
Q

what was the result of selective pressures on the symbiont genome?

A
  • the free-living cyanobacterial ancestor had several thousand genes
  • genes no longer required for endosymbiotic existence (eg. genes for flagella, cell wall, scavenging micronutrients) were quickly lost
  • genes for metabolic pathways duplicated by the host were lost
  • many genes were transferred from the cyanobacterium to the host nucleus
  • modern-day chloroplast contain a circular genome of 100-200 genes
  • roughly a 90-95% reduction in size and complexity compared to cyanobacterial genome
37
Q

what was the result of primary endosymbiosis?

A 
Chlorophyla = green algae (chlorophyll a, chlorophyll b)
Rhodophyta = red algae (chlorophyll a, phytobilins)
Glaucocystophyla = glaucos (chlorophyll a, phytobilins)
38
Q

explain why the study of volvox is so useful

A
  • simple model system for investigating multicellularity and cell differentiation
  • two cell types: a) small, flagellated somatic cells around the surface of the sphere; b) large germ-line cells embedded within the matrix of the sphere
39
Q

describe the main features of glaucocystophytes

A
  • relatively insignificant group of freshwater algae
  • only ~13 species described
  • interesting from an evolutionary perspective, since chloroplast has retained peptidoglycan cell wall of the original gram-negative cyanobacterium
40
Q

what are the stages of secondary endosymbiosis?

A
  1. capture of a photosynthetic eukaryote
  2. establishment of a symbiont
  3. symbiont reduced to an organelle
  4. nucleomorph lost
41
Q

what do Chlorarachniophytes and Cryptophytes have in common?

A
  • arose by separate endosymbiotic events involving a green and red alga, respectively
  • but they share the common feature of a nucleomorph
42
Q

what is so remarkable about Chlorarachniophytes and Cryptophytes?

A
  1. cells possess four genomes, each with a different evolutionary history:
    - nuclear genome (eukaryotic host)
    - nucleomorph genoms (eukaryotic alga)
    - chloroplast genome (cyanobacterium)
    - mitochondrial genome (α-proteobacterium)
  2. despite having different origins (red and green algae), the nucleomorph genomes show striking convergent evolution:
    - each has become miniaturised to form tiny chromosomes
    - with a few thousand tightly-packed genes
    - very little intergenomic space
    - ‘bonsai chromsomes’
43
Q

how did Euglena obtain its chloroplast?

A

in a separate ‘green alga’ endosymbiosis, in which the protozoan host was closely related to modern-day tryposomes

44
Q

how did the remaining algal groups obtain their chloroplasts?

A
  • by secondary endosymbiosis involving red algae
  • heterokonts (including diatoms and brown algae)
  • haptophytes (eg. Emiliana)
  • (probably) apicomplexa
45
Q

describe the main features of dinoflagellates

A
  • probably began with a chloroplast from a red alga
  • ~50% of species have discarded their chloroplasts (returned to being heterotrophs)
  • others replaced this with one from a green alga or a haptophyte(tertiary symbiosis)
  • others have temporary chloroplasts (kleptoplastids) obtained from their algal prey and maintained for a few months, without replication
    eg. sea slugs

BIOC1010 Dina (7 decks)

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