BIOL 112 1st Edition Lecture 10 Outline of Last Lecture I. Goal of SystematicsII. Systematics ApproachesIII. CladisticsIV.Phylogenetic TreesV. Problems with TechniquesVI.Hypothesis FormationVII. How many Kingdoms?VIII. DomainsOutline of Current LectureIX.Problems with Earliest DivergencesX. “LUCA”XI.The Prokaryotic CellXII. Cell Wall BiochemistryXIII. Gram Positive/Gram NegativeXIV. Ways to Organize the Cell WallXV. Structures Outside Cell MembraneXVI. Structures Inside Cell MembraneXVII. Metabolism/NutritionXVIII. AutotrophyCurrent LectureI. Problems with Earliest DivergencesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Mechanisms and events of origin of life not fully understood - not a very good recordVarious models proposed (ch. 25 & 27 in Campbell and supplemental booklet)Life arose perhaps as early as 750 x 10^6 years after Earth formed (at 4.5 x 10^9 yrs bp [bp = before present])Fossil record shows clear bacterial forms by about 3.5 x 10^9 yrs bp; some indirect evidence for life older than thatEarliest eukaryotic-like fossil forms at 1.5 - 2 x 10^9 yrsWhat is the lineage of early life forms?II. “LUCA”Last Universal Common AncestorPostulated ancestor of all life forms on planetDivergences from LUCA could be bases of definition of Domains, BUT:•Trans-species ("horizontal") transfers of genomic material (trans-formation, conjugation, transduction)•Endosymbiotic associations followed by genomic exchangesHow can we reconstruct lineages when there is no clear lineage of ge-nomic material from a single ancestor?III. The Prokaryotic CellDefine prokaryotes with positive, not negative, traits (i.e. DOESN'T have a nucleus.. should't define it that way)Negative traits make prokaryotes sound like merely defective eukary-otes, but they're not!Morphology:•Not a lot of diversity•Morphology is determined by cell wall•Bacilli - rods•Cocci - spheres•Spirilli - helical cells with external flagella•Vibrios - short, curved rods, "commas"•Spirochetes - long helical cells with axial filamentsCell Wall present in most prokaryotic forms. Cell wall prevents os-motic swelling; bacteria usually live in hypotonic environment for this reason.IV.Cell Wall BiochemistryComplicated polymer of amino sugar and short amino acid chainsComponents:•N-acetyl glucosamine•N-acetyl muramic acid (bacteria-specific)•PeptidesAll components are covalently cross linked into a giant polymer so that the cell wall is one large macromolecule called a peptidoglycan.V. Gram Positive/Gram Nega-tiveTwo basic arrangements ofcell wall components:•Gram Positive: Thickercell wall ~20 nm; wall is90% peptidoglycan, lipidcontent low (0-2%). Highlyresistant to ethanol extrac-tion, so gram stain will re-main in cell and leavedarkly stained cell. Purple/Blue.•Gram Negative: Thinner cell wall ~10-15 nm; contains only 20% peptidoglycan, higher lipid content (10-20%). High lipid contentmakes wall sensitive to ethanol extraction, so most of the gram stainwill be removed and leave weakly stained cell. Pink.VI.Ways to Organize the Cell WallGram positive cells are especially sensitive to penicillin (Penicillin in-hibits enzymes that synthesize cross links in wall.)Gram negative cells are less sensitive to penicillinMost prokaryotes (except mycoplasmas) have cell wall of this basic structure, although details of biochemistry might vary from taxon to taxonCell wall morphology/biochemistry is of significant taxonomic impor-tanceVII. Structures Outside Cell MembraneBacterial Flagellum Motility structure, not membrane covered, mostly 1 protein: flagellin. One or more per cell, distributed over sur-face or concentrated on the end of the cell•Fits into a socket in cell wall surface, base against cell membrane, spins like a little propeller to move cell around•Movement generated by interactions between base of flagellum and "motor" structures in socket, driven by H+ ion movementPilus (pl. Pili), or Fimbria (pl. Fimbriae) Shorter than flagella, rigid,non-motile•Extended from cell membrane surface, through cell wall, into envi-ronment•Several different types, function depends upon type and compo-nent proteins•Some function to attach bacterium to a surface or to specific recep-tors; one type functions in bacterial conjugation (sex pili)Capsule: Thick, gooey polysaccharide coat outside the cell wall, loosemesh of polymers•Sticks cells together like jello and forms a sticky film of materials to hold bacteria to surfaces•Aids bacteria to evade host defenses -- capsuled cell is harder for leukocyte to attack and eat, cause of most bacterial infections•Many bacteria with capsules are pathogenic -- cause diseasesVIII. Structures Inside Cell MembraneCell Membrane (or Plasma Membrane): Functional boundary be-tween cell and world: 7 nm thick; two layers of phospholipids with proteins floating. Similar to eukaryotic membranes, except no chole-sterol.Mesosome: Found in some microscope images of bacteria: a fold of membrane into the cytoplasm, looks like a whorl. Function unknown; most microbiologists do not accept existence, very likely an artifact of EM preparationCytoplasm (Cytosol): Not elaborately structured, not subdivided or compartmentalized. Exception: cyanobacteria (blue-green algae) have extensive arrays of photosynthetic lamellae. These are extensions of plasma membrane).Nucleoid: Compact mass of DNA usually in middle of cell, containing the genome of the bacterium. This is a circular DNA molecule and it isattached to the inner face of the plasma membrane at one side. Often called the bacterial chromosome. "Genophore" is a term that is also used sometimes.Plasmids: Smaller circles of DNA present in some cells, in addition tothe genome. Each contains anywhere from 2-30 or more genes, and might not code for genes found in the regular genome, or even code for essential genes. Plasmids control their own replication and segre-gation (e.g., F plasmid in E. coli)Ribosomes: Prokaryotic form: 70S, comprised of 30S and 50S sub-units. Smaller than eukaryotic cytosolic ribosomes, sensitive to a dif-ferent set of antibiotics than eukaryotic ribosomes. Archaean ribo-somes more like eukaryotic formsSpores: Endospores. Not all bacteria make these. Dormant resistant stage with extremely heavy cell wall and highly dehydrated cytoplasm.Virtually no metabolism•Resistant to drying•Resistant to