Micribio 12

18S rRNA genes for phylogeny of eukaryotes

Phylogenies have been constructed byt aking into account other genes (eg. tubulin, RNA polymerase, and ATPase)

Mitosomes and hydrogenosomes

• Reduced form of mitochondria
• Derived from mitochondria- that does not have enzyme of the TCA cycle and does not have a respiratory chain
• Thney are involved in maturation of iron-sulfur cluster containing proteins

• Present in eukaryotes whose metabolism is strictly fermentatie
• It caries the oxidation of pyruvate to H2, CO2 and acetate
• Sometimes H2-consuming endosymbiotic bacteria are also present (methanogens)
• Secondary endosymbiosis

Some species of protists are able to differentiate into cysts, becoming encysted

Cysts are similar to the endospore produced by prokaryotes

• Help protect the cells against deleterious environmental conditions
• Help survive long period of starvation and/or dessication
• Help survive infection by prokaryotes

• Unicellular
• Flagellated
• Lacks chloroplasts
• Live on anoic habitats

• Have 2 nuclei of equal size
• Have mitosomes (degenerated mitochondria)
• Key genera: giardia (causes giardiasis)

• Contain a parabasal body (structural support to the golgi complex)
• Lack micochondria, but have hydrogenosomes for anaerobic metabolism
• Live in the intestinal and urogenital tract of animals as parasites or symbiotins
• Key Genera: Trichomonas

• Parabasalid
• STDs in humans: most common parasitic infection in well developed countries
• Does not form cyst, does not survive well outside the host (adapted to sexual transmission)

• Unicellular flagellated eukaryotes
• ie Kinetoplastids

• Named for the presene o the kinetoplast, a mass of DNA present in their single large mitochondrion
• Live primarily in aquatic habitats feeding on bacteria
• Some species cause serious diseases i humans

• A kinetoplastid
• Cause African sleeping sickness, a chronic and usually fatal infection
• Lives and grows in the blood stream, infect the central nervous system during the later stage
• Transmitted by the tsetse fly
• The single flagellum is englosed in a membrane flap

• Nonpathodenic and phototrophic
• Contain chloroplasts, can exist as heterotrophs; will lose its chloroplast if incubated in the dark for a long term
• Can feed on bacteria by phagocytosis

• Characterized by the presence of alveoli, which are sacs underneath the cytoplasmic membrane
• May function to help cells maintian osmotic balance
• In paramecium: contractil vacuole
• Members are ciliates, dinoflagellates, and apicomplexans

• Possess cilia at some stage of their life
• Most widely distributed gnera are paramecium
• Use cilia for motility and to obtain food
• Ciliates have two nuclei (macronucleus and micronucleus)
• During conjugation- sexual reproduction- two paramecia exchange micronuclei
• Some ciliates are animal parasites, some are animal symbiotins (in the rumen)

Two paramecia exchange micronuclei

2: macronucleus and micronucleus

For motility and to obtain food

Divers marine and freshwater phototrophic organisms

• Have two flagella with different insertion points on the cell:
• Transverse flagellum
• Longitudinal flagellum

Red tides

• Associated with human poisoning (paralytic shellfish poisoning)
• Accumulation of toxic dinoflagellates in mussels

It is a genus of toxic dinoflagellate responsible for massive fish kills: spores infect fish, germinates, destroy tissue

Some secret neurotoxins

In warm, polluted water dinoflagellates can reach very high numbers

• Obligate parasites of animals
• Complex life cycle
• Contain apicoplasts, degenerate chloroplasts that lack pigments and phototrophic capacity, but still carry many anabolic pathways
• Cause severe desiease such as malaria (Palamodium), toxoplasmosis (toxoplama), and coccidiosis (Eimeria)

• Sporozoite (transmission)
• Gameotoyte (sexual reproduction)
• Other stage

Plamodium

Toxoplama

Eimeria

• Rats infected with the brain paraside Toxoplasma gondii approach the cat urine odors they typically avoid
• Toxoplasma infection alters neural avticity in limbic brain areas necessary for innate defensive behavior in response to cat odor

• All have flagella with many short hairlike extensions
• Chemoheterotrophs and phototrophic members
• Oomycetes, diatoms, golden algae, and brown algae

• Chemoheterotrophs
• Also called water molds based on their filamentous growth and the presence of coenocytic hyphae (multinucleate)
• Cell walls are made of cellulose, not chitin as in fungi
• Phytophthora inestans causes the late blight disease in potatoes and contributed to the Irish potato famine

• Also called chyrophytes
• Most are unicellular, some are colonial
• Golden algae are named because of their golden-brown color
• Chloroplast pigments dominated by the carotenoid fucoxanthin

• Unicellular, phototrophic
• Over 100,000 species of diatoms
• Contain frustules

Freshwater and marine habitats

• Cell walls made of silica with proteins and polysaccharides attached to it
• Protect against predation

200 million years ago

By their threadlike pseudopodia

• Exclusively marine organisms
• They form shell-like structures called tests
• Tests are made from organic materials reinforced with calcium carbonate

Made from organic materials reinforced with calcium carbonate

• Mostly marine, heterotrophic organisms
• Tests are made of silica
• Name is derived from radial symmetry of tests

Silica

• terrestrial and acquatic protists that use pseudopodia for movement and feeding (phagocytosis of bacteria and smaller protists)
• Move by amoeboid movement (cytoplasmic streaming)

• Gymnamoebas
• Entamoebas
• Slime molds

Free-living, inhabit soil and acquatic environements

Parasites of vertabrates and invertabrates

• Previously grouped with fungi because they have similar life cycle: produce fruiting bodies with spore for dispersal
• Motile, can move across surfaces rapidly

• Have vegtetative forms that are masses of protoplasm of indefinite size and shape that contain multiple nuclei
• From the plasmodium, a sporangium can form, cotnaining multiple haploid spores
• The spores germinates, yielding a flagellated swarm cells. The fusion of two swarm cels regenerates the diploid plasmodium

The fusion of two swarm cells regeerates the diploid plasmodium

Vegetative forms composed of single amoebae

Aggregate as a pseudoplasmodiu (slug) that can move as a single unit

May form diploid amcrocysts, undergo meiosis to form new aboebae