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Topic 4, Eukaryotes
Organelles
• Note: Both mitochondira and chloroplasts are semi-‐ autonomous – each has their own DNA, ribosomes, and transcripAon machinery – can replicate independently of the rest of the cell – most of their proteins originate from the DNA in the nucleus of the
cell
Plasma and Cell wall across Eukarya
Cytoskeleton and Flagella
Four Main Categories of Eukaryal Microbes
Note: highly conserved genes can be used to enhance our understanding of eukaryal phylogeny (e.g. tubulins, heat shock proteins)"
Fungi -‐-‐ Saccharomyces cerevisiae • heterotrophic; cell walls of chiAn;
used to make bread, beer, wine! • easy, cheap tool to study
eukaryoAc structures/gene expression
• Saccharomyces can undergo meiosis to form an ascus
• Haploid maAng types can fuse to reproduce sexually or be maintained by asexual mitosis
• Saccharomyces not limited to ascus formaAo
• budding off of smaller cells can occur or fission of idenAcally sized cells
Protozoa
• As a whole, a (very) broad category
• Some heterotrophic, some photosyntheAc
• Variable cell walls • Different moAlity strategies • Different reproducAon strategies • Model Organism = Giardia lamblia
– geneAcally “old”, lacks mitochondria – causes human disease
Slime Moulds -‐-‐ Dictyostelium discoideum
• sAll protozoan • model for studying ecology, cell
moAlity, and cell-‐cell communicaAon • Has three types of cycles:
– VegetaAve cycle: exists in a haploid unicellular form unAl condiAons worsen then will go to social cycle.
– Social Cycle: mulAcellular “slug” is formed with a stalk and a fruiAng bodyspores form in the fruiAng body, restarAng the life cycle as haploid cells
– Sexual Cycle: • haploid cells can fuse into a diploid
macrocyst form • macrocyst form undergoes meiosis to
generate more haploid cells
Algae -‐-‐ Chlamydomonas • Many mulicellular with cellulose cell walls • has a two-‐flagella form good for studying eukaryal flagella
biogenesis/funcAon • durable and easy to grow • Chlamydomonas maintains a moAle haploidstate • haploid cells dierenAate and fuse into a diploid form in bad
condiAons– spore formaAon
EndosymbioAc Theory • one primiAve microbe ingested another,
forming a symbiosis • two endosymbioAc events must have
occurred: – Mitochondria – Chloroplasts
• Evidence for EndosymbioAc Theory: – mitochondria/chloroplasts resemble
bacteria in both size and shape. • double membranes • “Cell” division with FtsZ • each has its own DNA, rRNA more similar
tobacterial sequences than eukaryal ones • circular chromosome
– EXCEPTION: Amitochondriates lack mitochondria. Cells likely evolved out of using them to obtain energy. Ex) Giardia
Diseases Caused by Eukaryal Microbes
• Protozoa: – The tricky things about these pathogens is that they
are very similar to the cells that they are taking over so, tough to harm it w/out harming human. Includes: • Malaria and African Sleeping Sickness
• Fungi: – are less likely to cause disease, but can do so in
immuno-‐compromised individuals – Includes:
• Candida albicans, causes oral thrush • Epidermophyton floccosum, causes Athlete’s foot
• Protozoa and fungi can cause significant disease in plants but, must wait for the cell wall to become damaged – Fungi:
• RHYTISMA -‐ "tar spot" these are the infecAons on the maple trees. Means low air polluAon.
• Phytophthora infestans -‐ potato blight – Protozoa:
• CORDYCEPS -‐ are specific to each arthropod. Cause them to go mad and then form a fruiAng body out of their bodies.
Beneficial Roles of Eukaryal Microbes
• primary producers provide energy
• some algae produce great amounts of oxygen through photosynthesis in the oceans
• biodegraders recycle nutrients • some eukaryal microbes can degrade cellulose, recycling plant macer becer than animals can