Topic 4 Eukaryotes PDF 2022

Topic 4 Eukaryotes  Topic 4 Eukaryotes The morphology of typical eukaryal cells Diversity of eukaryal microorganisms Replication of eukaryal microorganisms The origin of eukaryal cells Interactions between eukaryal microrganisms and anima...

Topic 4 Eukaryotes  Topic 4 Eukaryotes The morphology of typical eukaryal cells Diversity of eukaryal microorganisms Replication of eukaryal microorganisms The origin of eukaryal cells Interactions between eukaryal microrganisms and animals, plants, and the environment  g y ol o p h or M Morphology of Typical Eukaryotes membrane- bound nucleus larger than bacterial or archaeal cells contain organelles possess a cell wall and complex internal cytoskeleton Figure 3.1 Organelles  The Nucleus plays a role in the storage and expression of information double membrane structure contains linear chromosomes of cell non-membrane bound nucleolus exists within nucleus (ribosome synthesis) spatial separation transcription occurs in nucleus translation occurs in cytoplasm Figure 3.2  The Secretory Pathway uses ER/Golgi apparatus proteins are often extensively modified in these structures prior to reaching their destinations Figure 3.3  Mitochondria “Powerhouses of the cell” Play a role in cell metabolism – TCA cycle Use electron transport chains to produce ATP (chemiosmosis via the proton motive force) Figure 3.4  Chloroplasts play a role in cell metabolism use electron transport chains to produce ATP (chemiosmosis via the proton motive force) use the ATP they produce to fix carbon into organic compounds (e.g., glucose) Figure 3.4 Both mitochondria and chloroplasts are semi-autonomous each has a DNA genome, ribosomes, and transcription 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 Membrane phospholipid bilayer with embedded proteins that allow molecule transport facilitated diffusion (no energy required from cell) active transport (cell expends energy) plays a role in homeostasis maintaining a constant internal environment Wikipedia  Cell Wall plays a role in cell support broad separation between those with and those without cell walls cell walls can vary widely between the domains  Cellulose and Chitin use specific b-1,4- glycosidic bonds between sugars provides strength and rigidity Figure 3.5  Cytoskeleton has a role in cell structure comprised of three major pieces: microtubules (tubulin) microfilaments (actin) intermediate filaments (various proteins) each differs in structure/function; all contribute to cell shape The cytoskeleton is also involved in intracellular trafficking, motion, and cell division can be observed via fluorescent microscopy Figure B3.3 Figure B3.4 cell division is assisted by spindle fibers Figure 3.6 Motion achieved by cilia/flagella very different structure than for bacteria Motion achieved by cilia/flagella very different structure than for bacteria nine microtubule doublets form a tube around a core pair of microtubules (the axoneme) motion occurs when ATP is burned, helping microtubules in the axoneme slide past each other Figure 3.7  Figure B3.5 pathogens can exploit the cytoskeleton e.g. HSV, Listeria Figure B3.6  i ty rs i ve D  Eukaryote Diversity Figure 3.8  highly conserved genes can be used to enhance our understanding of eukaryal phylogeny (e.g., tubulins, heat shock proteins) Figure 3.9 Categories of eukaryotic microorganisms Pseudopodia on amoeba  s is m an rg l o d e Mo  Fungi Saccharomyces cerevisiae heterotrophic; cell walls of chitin; used to make bread, beer, wine easy, cheap tool to study eukaryotic structures/gene expression Figure 3.10 Figure 3.10  Fungal phylogeny Chytridiomycota: early branching, “watermolds”, Laurel Creek banks Zygomycota: Rhizopus, bread mold!, lab contamination Glomeromycota: mycorrhizal fungi – extremely important for plants/trees. Ascomycota: “spore shooters”, cup/sac fungi, yeast Basidiomycota: “spore droppers”, “club fungi”, traditional mushroom producing fungi  Protozoa As a whole, a (very) broad category some heterotrophic, some photosynthetic variable cell walls different motility strategies different reproduction strategies Figure 3.11 Giardia lamblia genetically “old”, lacks mitochondria causes human disease Figure 3.11  Slime Moulds Dictyostelium discoideum model for studying ecology, cell motility, and cell-cell communication Physarum fuses many cells into a continuous, multinucleate giant cell Figure 3.12  Algae many are multicellular all are photosynthetic with cellulose cell walls Chlamydomonas has a two-flagella form good for studying eukaryal flagella biogenesis/function durable and easy to grow  i on at p lic Re  Replication of Eukaryotic Microorganisms life cycles are more complicated due to haploid/diploid states possibilities for sexual or asexual reproduction  Mitosis basic cell division produces two identical cells from one original cell Figure 3.13  Meiosis four haploid cells from one original diploid cell one round of DNA replication followed by two rounds of cell division genetic recombination segregation of maternal/paternal chromosomes “crossing over” between chromosomes prior to segregation ensures each haploid cell is genetically distinct Figure 3.14  Saccharomyces Life Cycle Saccharomyces can undergo meiosis to form an ascus haploid mating types can fuse to reproduce sexually or be maintained by asexual mitosis Figure 3.15 FUNGUS  Saccharomyces not limited to ascus formation budding off of smaller cells can occur or fission of identically sized cells Figure 3.16  Chlamydomonas Life Cycle Chlamydomonas maintains a motile haploid state haploid cells differentiate and fuse into a diploid form in bad conditions – spore formation ALGAE Figure 3.17  Dictyostelium Life Cycle exists in a haploid unicellular form until conditions worsen multicellular “slug” is formed with a stalk and a fruiting body spores form in the fruiting body, restarting the life cycle as haploid SLIME MOULD cells haploid cells can fuse into a diploid macrocyst form macrocyst form undergoes meiosis to generate more haploid cells  i ns rig O Endosymbiotic Theory life started 4.5 to 4 bya, but eukaryotes appeared around 2.1 to 1.6 bya one primitive microorganism (archaea) engulfed/ingested another (bacteria), forming a symbiosis at least two endosymbiotic events must have occurred mitochondria chloroplasts Figure 3.18  Evidence for Endosymbiotic Theory mitochondria/chloroplasts resemble bacteria in both size and shape. double membranes (host and bacterium) “Cell” division with FtsZ each has its own DNA, rRNA more similar to bacterial sequences than eukaryal ones circular chromosome EXCEPTION: Amitochondriates lack mitochondria. Cells likely evolved out of using them to obtain energy (Giardia is an example)  Endosymbiosis in Modern Cells Two cells together are better than one alone Figure 3.19 Paramecium ingesting algae and using them for photosynthesis Figure 3.20  Lingering Questions About Endosymbiotic Theory If we can show it occurs in experiments, why has it only been stable twice in history? What was the thing that was first engulfed, exactly? How did the initial “engulfing” deal with a cell wall structure, if there was one? Are other organelles the result of endosymbiosis? The nucleus has a double membrane as well….  ns ti o a c e r Int  Diseases Caused by Eukaryal Microbes protozoa can cause significant human diseases Malaria African Sleeping Sickness Figure 3.21 Fungi are less likely to cause disease, but can do so in immuno-compromised individuals Figure 3.22 protozoa and fungi can cause significant disease in plants potato blight and the great Irish famine, mid-1800’s Figure 3.23  Rhytisma “Tar Spot” Rhytisma is an Ascomycete fungus, plant parasite that infects sycamores and maples in late summer, causing “Tar Spot”. Cordyceps 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 matter better than animals can Figure 3.24 e.g. termite gut protozoa