BIOL 112 1st Edition Lecture 10 Outline of Last Lecture I Goal of Systematics II Systematics Approaches III Cladistics IV Phylogenetic Trees V Problems with Techniques VI Hypothesis Formation VII How many Kingdoms VIII Domains Outline of Current Lecture IX Problems with Earliest Divergences X LUCA XI The Prokaryotic Cell XII Cell Wall Biochemistry XIII Gram Positive Gram Negative XIV Ways to Organize the Cell Wall XV Structures Outside Cell Membrane XVI Structures Inside Cell Membrane XVII Metabolism Nutrition XVIII Autotrophy Current Lecture I Problems with Earliest Divergences These 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 record Various 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 that Earliest eukaryotic like fossil forms at 1 5 2 x 10 9 yrs What is the lineage of early life forms II LUCA Last Universal Common Ancestor Postulated ancestor of all life forms on planet Divergences from LUCA could be bases of definition of Domains BUT Trans species horizontal transfers of genomic material transformation conjugation transduction Endosymbiotic associations followed by genomic exchanges How can we reconstruct lineages when there is no clear lineage of genomic material from a single ancestor III The Prokaryotic Cell Define 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 eukaryotes 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 filaments Cell Wall present in most prokaryotic forms Cell wall prevents osmotic swelling bacteria usually live in hypotonic environment for this reason IV Cell Wall Biochemistry Complicated polymer of amino sugar and short amino acid chains Components N acetyl glucosamine N acetyl muramic acid bacteria specific Peptides All 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 Negative Two basic arrangements of cell wall components Gram Positive Thicker cell wall 20 nm wall is 90 peptidoglycan lipid content low 0 2 Highly resistant to ethanol extraction so gram stain will remain in cell and leave darkly stained cell Purple Blue Gram Negative Thinner cell wall 10 15 nm contains only 20 peptidoglycan higher lipid content 10 20 High lipid content makes wall sensitive to ethanol extraction so most of the gram stain will be removed and leave weakly stained cell Pink VI Ways to Organize the Cell Wall Gram positive cells are especially sensitive to penicillin Penicillin inhibits enzymes that synthesize cross links in wall Gram negative cells are less sensitive to penicillin Most prokaryotes except mycoplasmas have cell wall of this basic structure although details of biochemistry might vary from taxon to taxon Cell wall morphology biochemistry is of significant taxonomic importance VII Structures Outside Cell Membrane Bacterial Flagellum Motility structure not membrane covered mostly 1 protein flagellin One or more per cell distributed over surface 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 movement Pilus pl Pili or Fimbria pl Fimbriae Shorter than flagella rigid non motile Extended from cell membrane surface through cell wall into environment Several different types function depends upon type and component proteins Some function to attach bacterium to a surface or to specific receptors one type functions in bacterial conjugation sex pili Capsule Thick gooey polysaccharide coat outside the cell wall loose mesh 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 diseases VIII Structures Inside Cell Membrane Cell Membrane or Plasma Membrane Functional boundary between cell and world 7 nm thick two layers of phospholipids with proteins floating Similar to eukaryotic membranes except no cholesterol 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 preparation Cytoplasm 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 is attached 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 to the 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 segregation e g F plasmid in E coli Ribosomes Prokaryotic form 70S comprised of 30S and 50S subunits Smaller than eukaryotic cytosolic ribosomes sensitive to a different set of antibiotics than eukaryotic ribosomes Archaean ribosomes more like eukaryotic forms Spores 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 chemicals Resistant to heat Can last 100 years or more Spores wait for appropriate environmental conditions then absorb water and emerge from spore as vegetative bacterium Binary Fission Asexual reproduction Cell Division split