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What is a protist? paraphyletic • no trait that is unique to protists • key features have often evolved more than once • Multicellular • Presence of endosymbiosis • Cell wall outside or inside of the plasma membrane • Motile: cilia, flagella, amoeboid motion • Sexual & asexual
Why should we study protists? Medical - chagas disease (kissing bug) & malaria (mosquito) Ecological - primary producers in oceans, marine C cycle
Marine carbon cycle o protists incorporate carbon into hard structures o carbon-full structures (foraminifera shells) accumulate on ocean floor o huge carbon sink carbon cycle speeds up if marine ecosystem fertilized with iron
Chagas disease • Zoonotic disease – reservoir hosts wood rat, dogs, cats, and opossums • Beetle is vector – parasite multiplies, enters system through open wounds.
Key features of protsits -there are a ton, very diverse -nuclear envelope (root of eukaryotes) -mitochondria – endosymbiosis -supercell -amoeboid form -plant chloroplasts
Formation of nuclear envelope • infolding of plasma membrane o elaborated by mutation and selection • formation of nuclear envelope: separates transcription from translation o new mechanisms of gene regulation • formation of endoplasmic reticulum: Translation of RNA to protein
Formation of mitochondria • bacteria is engulfed by ancestral eukaryote, it survives, and resides within. Mitochondria produce ATP • Evidence to support endosymbiosis o Mitochondrial DNA places them as a sister-group to a proteobacteria o Phylogentic evidence
2 mitochondria hypotheses • H1 – ancient amoeba-like eukaryote engulfed in a bacterium: resulted in failed • H2 – endosymbiosis between prokaryotes: archaeal host and a bacterium o Leads to mutualistic interactions o Additional membrane
Formation of chloroplasts • photosynthetic protist is engulfed, nucleus from photosynthetic protist is lost, organelle has 4 membranes
Red algae • human health o red algae produce mannose-binding lectins (protein) to fight off viral infections o mannose-binding lectins break down glycoprotein cell wall of viruses o mannose-binding lectins given to mice result in immunity to ebola
Foramaniferans • morphology o calcium carbonate shells • bio-indicators of pollution o species richness, morphology, shell chemistry, metabolic activity • important stratigraphic marker o allows interpretation of paleo-ecology and time periods
Dinoflagellates • causes toxic algal blooms (red tide) • detrimental to animals • results in hypoxia • toxins into human food chain through filtering organisms, such as oysters & clams
Bacteria and Archaea (Prokaryote) Diversity Bacteria was common ancestor of all life, proks are paraphyletic, proks have most biomass
Bacteria & Archaea similarities • no membrane around DNA o single circular chromosome • no energy-producing organelles • very few cell compartments • no sexual reproduction, yet huge diversity
Bact vs Arch vs Euk p 1 DNA closed by nuclear envelope? • Bact no • Arch no • Euk yes Circular chromosome present • Bact yes • Arch yes • Euk no Organelles enclosed by membranes? • Bact No • Arch no • Euk yes
Bact vs Arch vs Euk p 2 Rotating flagella? • Bact yes • Arch yes • Euk no (flagella and cilia) Multicellular species • Bact no • Arch no • Euk yes
Value in knowing about Bacts & Arcs? -oldest bacterium 3.5 Ga -oldest euk 1.75 Ga -what to find a new species? Look at bacteria & archaea -total number of bacteria and archaea 5x10^30 • if all lined up side by side, they’re longer than the milky way
Extremophiles (Bacts & Arcs) -10,000m depth -temp > 120 C (boiling of water or greater) -pH<1 -water saturated with salt -water temp of 0 C (freezing)
Medical (Bacts & Arcs) -archaea causes periodontitis (receeding gumline) -most bacteria are not pathogenic (disease causing). Most are decomposers & energy creators -what makes a bacterium pathogenic? • Heritable • Have larger genome with genes coding for protein toxin
Antibiotics • naturally produced by fungi and soil dwelling bacteria • extensive use in medicine & animal feed led to resistant strains • biofilm of bacteria growing in polysaccharide matrix reduces effects of antibiotics
Bioremediation -use of bacteria and archaea to clean up polluted sites • break-down compounds toxic to eukaryotes • examples: oil spills, arsenic -methods • enhance growth of bacteria already there • seed contaminated areas with specific bacteria
Morphological diversity (Bacts & Arcs) -tree of life • based on ribosomal RNA. Matrix made of ribosomes. -variation • size o 0.3 to 100 um • shape o round, squiggly, rod • motility
Horizontal gene transfer -in general, bacterial genomes smaller bc they lack non-coding DNA -lack sexual repro & cell fusion but have lots of diversity o Conjugation • Pilus connection o Transformation • As a bacteria dies, it releases DNA. It’s taken up by a live bacteria
Morphological diversity (Bacts & Arcs) part 2, cell walls -cell wall structure • gram-positive have pepdoglycan o use penicillin • gram-negative o arythromiacin
Metabolic diversity (Bacts & Arcs) -aerobic water -anaerobic water -anaerobic sediment -proks have lots of metabolic diversity, while euks have more multicellular diversity
Metabolic diversity remix: Where do you get your energy? -photoauto • E - sun & C - CO2 (cyano, plants and algae) -chemoauto • E - chem reactions & C - CO2 (unique to proks) -photohetero • E - sun & C - enviro (heliobacteria) -chemoheterotrophs • E & C from enviro (many proks & fungi, and animals)
Conclusions about proks & euks -some biologists suggest phylogenetic tree of proks should be viewed as a series of diverting branches that reconnect as new organisms because of lateral gene transfer -astrobiology studies extremophile possibilities on other planets
Created by: haleyBUGoxox