Question | Answer |
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 |