BIO 1306: Exam IV

Bacteria & Archaea

  • Prokaryotes thrive in harsh conditions; masters of adaptation.
  • Divided into two domains: Bacteria and Archaea.

Bacteria Characteristics

  • Unicellular, some form colonies.
  • Small (0.5-5 microns).
  • Variety of shapes: cocci (spherical), bacilli (rod), spirilla/spirochete (spiral).
  • Cell wall contains peptidoglycan.
  • Gram positive: simple walls, large peptidoglycan amounts, more susceptible to antibiotics.
  • Gram negative: complex walls, less peptidoglycan, LPS layer, more drug-resistant.
  • Endospore: resistant form when nutrients lacking; killed by autoclave.
  • Fimbria: hair-like, for binding.
  • Pilus: longer, for plasmid DNA exchange.
  • Flagella: movement; evolved through exaptation.
  • DNA: no nucleus, circular, in nucleoid region; plasmids present.

Genetic Diversity of Bacteria

  • Rapid reproduction: binary fission, short generation times.

  • Mutation accumulation: quick life cycle, mutations accumulate rapidly.

  • Genetic recombination: transduction, transformation, conjugation.

    • Transduction: phage infection transfers DNA.
    • Transformation: uptake of free DNA.
    • Conjugation: direct contact transfers plasmid DNA; requires pilus.

Nutrition Modes

  • Photoautotrophs: use light to synthesize organic compounds from CO2.
  • Chemoautotrophs: oxidize inorganic substances for energy, use inorganic CO2.
  • Photoheterotrophs: use light for energy, require organic carbon.
  • Chemoheterotrophs: consume organic molecules for energy and carbon; includes animals.

Metabolism and Oxygen

  • Obligate aerobes: require O2.
  • Facultative anaerobes: use O2 or fermentation.
  • Obligate anaerobes: poisoned by O2, use fermentation or anaerobic respiration.
  • Nitrogen-fixing prokaryotes: require light, N2, water, minerals; form biofilms.

Prokaryotic Lineages

  • Bacteria and Archaea Domains

Proteobacteria

  • Gram-negative.
    • Alpha: related to mitochondria, includes Rhizobium (nitrogen fixers).
    • Beta: nitrogen cyclers.
    • Epsilon: pathogenic, e.g., Helicobacter pylori.
    • Gamma: pathogenic, gut bacteria (E. coli, Salmonella).

Other Bacteria

  • Spirochetes: spiral-shaped, Lyme disease.
  • Cyanobacteria: photoautotrophs, generate O2, related to chloroplasts.

Archaea

  • Extremophiles: halophiles (salt lovers), thermophiles (heat lovers).
  • Methanogens: produce methane (CH4), strict anaerobes.

Ecological Roles

  • Major decomposers: recycle nutrients.
  • Nitrogen-fixers: convert N2 to usable forms.
  • Symbiosis: commensalism, parasitism, mutualism.

Human Uses

  • Bioremediation: remove toxins.
  • Recombinant bacteria: produce proteins, hormones.
  • Biodegradable plastic: PHA production.
  • CRISPR-Cas9: genome editing.

Protists

  • Informal designation for eukaryotes that are not plants, animals, or fungi.
  • Mostly unicellular; diverse nutrition (photoautotrophs, heterotrophs, mixotrophs).
  • Diversity from endosymbiosis.

Endosymbiosis

  • Primary: ancestral archaean engulfed alpha proteobacteria (mitochondria) and cyanobacteria (chloroplasts).
  • Secondary: red and green algae engulfed by other eukaryotes.

Protist Supergroups

  • Excavata:
    • Defined by cytoskeleton, excavated feeding groove.
    • Includes Diplomonads, Parabasalids, Euglenozoans.
  • SAR (Stramenopiles, Alveolates, Rhizarians):
    • Stramenopiles: Diatoms, golden algae, brown algae.
    • Alveolates: Dinoflagellates, apicomplexans, ciliates.
    • Rhizarians: Radiolarians, forams, cercozoans.
  • Archaeplastida: red algae, green algae, plants.
  • Unikonta: amoebozoans, opisthokonts.

Stramenopiles

  • 2nd endosymbiosis from red algae.
    • Diatoms: unicellular algae, silicon dioxide walls.
    • Golden algae: yellow and brown carotenoids.
    • Brown algae: multicellular seaweeds; fucoxanthin.

Alveolates

  • Have alveoli (membrane-bound cavities).
    • Dinoflagellates: cellulose plates, two flagella, red tides.
    • Apicomplexans: parasites, sporozoites.
    • Ciliates: use cilia for movement and feeding, macronuclei and micronuclei.

Rhizarians

  • Threadlike pseudopodia.
    • Radiolarians: silica skeletons.
    • Forams: calcium carbonate tests; fossil forms indicate climate.

Archaeplastida

  • Red algae: phycoerythrin.
  • Green algae: grass-green chloroplasts.

Unikonts

  • Amoebozoans: lobe- or tube-like pseudopodia, slime molds, entamoebas.

Ecological Roles of Protists

  • Symbionts: can be beneficial or detrimental.
  • Primary producers: photosynthetic protists.

Plant Diversity I

  • Key traits with charophytes: rings of cellulose-synthesizing proteins, flagellate sperm structure, phragmoplast formation, sporopollenin prevents desiccation.
  • Traits distinguishing plants from charophytes: alternation of generations, multicellular dependent embryos, multicellular sporangia produce walled spores, multicellular gametangia producing gametes, apical meristems.
  • Additional traits: cuticle, stomata, mycorrhizae.
  • Nonvascular plants (bryophytes): liverworts, mosses, hornworts; gametophyte dominant.
  • Seedless vascular plants: sporophyte dominant, xylem and phloem, roots and leaves.
  • Lycophytes and Monilophytes: Extant species; require water for fertilization.
  • Sporophylls : modified leaves that contain sporangia; Sori=clusters of sporangia
  • Strobili=cone-like structures