Eukaryotic microbes Flashcards
Protozoa
‘first animals’
- single cell eukaryotes
- lack a rigid cell wall, are generally motile and inhabit ‘wet’ environments
- are heterotrophs
- some species are parasites of animals or plants
Algae
- essentially, protozoa that have a plastid
- those algae in which the plastid is a chloroplast are phototrophs
protozoa as human parasites
Trypanosomes- african sleeping sickness
Leishmania- leishmaniasis (dumdum fever)
Entamoeba- amoebic dysentery
phytophthora
P.infestants- potato blight
P.palmivora- affects cocoa pods
Dinoflagellates
Causes red tides. Produce neurotoxins that can build up in fish, leading to paralytic neurotoxin, where when we eat it we suffered the effects. Can also remove all oxygen out of water and kill the fish
Probably began with a chloroplast from a red alga. 50% since discarded their chloroplast, others replaced this one from a green alga or haptophyte, other have temporary chloroplasts (kleptoplastids) obtained from their algal prey
Diatoms
Eukaryotes in glass houses. Accumulate silica from the ocean. Dynamite- key ingredient is diatomaceous earth- blended with nitroglycerine to create a safe explosive
Evolution of the eukaryotes
Believed to evolve from the prokaryotic Archaea, through a process of internal membrane formation, cell enlargement and serial endosymbiosis
The alveolates
So called because the cells possess alveoli
Ciliates, Sporozoans, Dinoflagellates
Ciliates
the most complex single celled organisms
found almost anywhere there is water
some/all of the cell surface is covered with cilia to propel through water or draw in food particles
feed on bacteria, algae or even other ciliates
ciliates in soils form cysts in order to survive long periods of drying
Sporozoans
Haploid parasitic protozoa, habe complex life cycle usually involving growth stage within host cell
subgroup- apicomplexans- have distinctive structure at apical end of sporoazoite (involved in host cell invasion)
Euglenoids
Flagellated protozoa including; Euglena, Trypanosomes, Leishmania
Euglena
Many species of the genus possess chloroplasts, but are also capable of heterotrophic growth. In some species the chloroplast is easily lost
obtained their chlorplast in a separate green alga endosymbiosis in which the protozoan host was closely related to modern day trypansomes
Trypanosomes
Flagellated pathogens of animals and plants. Life cycle involves an insect host. Possess a kinetoplast
Oomycetes
so called “water moulds”. filamentous protozoa that may be free-living or parasitic. Many grow as ‘fungal-like’ hyphae and appear as rusts or mildews. originally considered to be fungi, now clear that they are related to the chromista
Sarcodina
Largest phylum of protozoa. comprises the amoeba- unicellular protozoa that use pseudopodia for locomotion and feeding.
Most species free living, although some important parasites
Entamoeba histolytica
A major human pathogen. two stages in life cycle: a) motile amoeba B) cyst
Ingested cysts are resistant to stomach acid and hatch to form amoebae in colon. New cysts form and pass through the bowel. Normally no symptoms, but in some individuals amebae becomes invasive and attacks organs, resulting localised infection or systemic infection including the brain
Dictyostelium discoideum
A clever little amoeba
Haploid unicellular amoeba feeds on bacteria in soil and divide by mitosis. But when food source becomes scarce, then it undergoes a developmental change. Amoeboid movement exploited to create a multicellular organism. Cells secrete cAMP that attracts other cells. These adhere via glycoproteins expressed on cell surface. The slug then moves to new environment and differentiates. when mature, releases spores
Evolution of algae
chloroplast arose from a cyanobacterium
free-living cyano was engulfed by a feeding amoeba
rather than being digested, the cyano became an endo-symbiont-providing fixed carbon and oxygen to its host in return for a safe, nutrient rich niche
over time, there was a transition for facultative symbiont to obligate symbiont to organelle
3 lineages from primary endosymbiosis
chlorophyta (green algae)
rhodophyta (red algae)
Glaucocystophyta
The different pigment compositions in lineages
Chlorophyta- chl.a and chl.B
Rhodophyta- Chl.a and phycoblinis
Glaucocystophyta- Chl.a and Phycobilins
Glaucocystophyta
Relatively insignifcant group of freshwater algae
chloroplast retained peptidoglycan cell wall of the original Gram negative cyanobacterium
secondary endosymbiosis
acquiring a second-hand chloroplast
A eukaryote within a eukaryotes 1) capture of a photosynthetic eukaryote 2) establishment of a symbiont 3) symbiont reduced to an organelle 4) Nucleomorph lost
chlorarachiniophytes and cryptophytes
arose by separate endosymbiotic events involving a green and red alga
- the cells possess four genomes
a nuclear genome from the eukaryotic host
a nucleomorph genome from the eukaryotic alga
a chloroplast genome from a cyanobacterium
a mitochondrial genome from an alpha-proteobacterium
remaining algal groups that acquired their chloroplast by secondary endosymbiosis involving red algae
The heterokonts
the haptophytes
Apicomplexa
Apicomplexa
have retained a non-pigmented plastid with a reduced genome- various antibiotics target the bacterial RNA polymerase or ribosome are effective against some apicomplexan species
sea slugs
another example of kleptoplastidy
