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CU-Boulder EBIO 3400 - Mapping Microbes on the Tree Life
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EBIO 3400 1nd Edition Lecture 4Outline of Current LectureI. Mapping microbial diversity onto the tree of life II. The phylogenic distribution of pathogenic organisms III. Prokaryotic cell structure I. Mapping microbes on the tree life A. 2 Hypothesis’ 1) Life evolved in a warm place – hydrothermal or geothermal settings – maximum growth temp (thermophiles and hyperthermophiles are nearer to the root on the tree) 2) Adaptation to warm places requires mutations in genes that confer thermostability - making these genes look different that the othersB. Phylogenic distribution N-fixation known in Bacteria and Archaea- Why is N-fixation distributed in this manner - evolutionary loss, or gain via horizontal (or lateral) gene transfer events ex: Symbioses with plantsC. Why isn’t N-fixation universal? Why isn’t there an N-fixing Eukaryotic organelle (like chloroplast or mitochondrion)? Energy intensive, Carried out in the absenceof oxygenà ancient trait. Totally absent in the Eukarya D. Phylogenetic distribution of phototrophy – Endosymbiosis 1) Photosynthesis, seen in Bacteria, conferred to Euks via ancient endosymbioticevent involving cyanobacteria2) All of the eukaryotes that do this, do it with a chloroplast: organelle that is anendosymbiotic bacterium E. Endosymbiotic theory 1) Sequencing shows that: chloroplasts are cyanobacteria and mitochondria are alphaproteobacteria2) Idea that chloroplast and mitochondria are some ancient bacteria that engulfed: allowed the evolution of plants3) Isolate a chloroplast from plants - find a remnant chromosome that has bacterial genes that are places of chloroplast in cyanobacteria when DNA sequencedà bacteria enslaved a long time ago can’t live alone anymore A. Endosymbiosis: The mitochondrion 1) The theory that mitochondria jumped earlier through different lineagesThese 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.2) Most likely conclusion: the last common ancestor of all eukaryotes possessed a mitochondrion F. Horizontal gene transfer – very common in bacteria 1) Genes enter and leave genomes: Both rRNA trees and whole-genome trees consistently reflect monophyletic descent (black lineages) down to the genus level. Below the genus level, monophyletic descent may be obscured by high rates of horizontal transfer (colored lines entering, gray lines departing). Whitespaces indicate genes lost by reductive evolution2) 16s rRNA genes are not horizontally transferred so are still useful to classify microbes – So embedded in organism and hard to replace so 16s rRNA not swapped3) Shows the jump of the mitochondria and chloroplast à organism transfer II. The phylogenic distribution of pathogenic organisms A. Found in bacteria, actinobacteria, fermicutes, EukaryaB. Why are there no pathogenic archaea? Pathogenic archaea parasitize other archaeaIII. DNA sequencingA. Most organisms cannot be grown in the laboratory, evolved in such tight nichesDNA sequencing technology getting better people can more easily label DNA in environment and study organisms that you cant grow in the lab: environmental sequencing IV. Prokaryotic cell structure Morphology: the shape of thingsA. Two main shapes of bacteria1) Spheres: cocci (singular: coccus)2) Rods: bacilli (singular: bacillus)Other shapes: 4) Comma shaped: vibrio (ex: vibrio cholerae)5) Spiral: spirillum (ex: spirochete) 6) Varying shapes: pleomorphic (take different shapes, don’t have real cell walls)7) Unusual cell shapes: square archaeal cell, starfish branched shaped importantfor increase surface area of cell wall to take un nutrientsC. Cell grouping - Bacteria are often single cellsA. Chains: cell divides in one plane (ex: diplococcus à Neisseria aka gonorrhea) - Chain of cocci: streptococcus B. Packets: cell divides in two more planes (symmetrical packet of 4 or more cells) e.g. Sarcina C. Clusters: cell divides in several planes at random, looks like grapes. E.g. staphylococcus D. Archaea: Methanosarcina: makes methane and fixes N2, form packets that look like brains. - Anaerobically E. Different kinds of elaborate morphologiesA. Complex multicellular morphology in various cyanobacteria:1) Spiral trichome of Spirulina 2) Oscillatoria – multicellular cyanobacteria 3) Streptomyces: Filamentous hyphae of an actinobacterium, have multicellular hyphae and spherical spores (conidia) -“myces” comes from groups in fungi V. Prokaryotic cell structure (continued)A. The plasma membrane: every cell whether it’s prokaryotic or eukaryotic has a plasma membrane. Separates the inside of the cell from the environment - Very thin – about 8 nmB. Functions of the plasma membrane: permeability barrier prevents the leakage of cell materials into and out of cell - Proton motive force: for ATP generation, separates protons (H+) from hydroxyl ions (OH-) across its surface * Bacteria don’t have mitochondria but it kind of acts like one C. The cell membrane: the structure that defines the existence of a cell. Consists of a phospholipid bilayer with hydrophobic fatty acid chains directed inward, away from waterD. Membrane lipids1) Membranes have approximately equal parts of phospholipids and proteins2) A phospholipid consists of glycerol with ester links to two fatty acids and a phosphoryl head group – may have side chain 3) Membrane proteins have numerous functions: structural support, detection of environmental signals, secretion of virulence factors and communication signals, ion transport and energy storage* Have hydrophilic and hydrophobic regions that lock the protein in the membrane4) In eukaryotic membranes, the reinforcing agents are sterols, such as cholesterol. In bacteria, the same function is filled by hopanoids, or hopanes* Survive longer when have longer chains E. How do prokaryotes protect their cell membrane?- For most species, the cell envelope includes at least one structural supporting layer (most common structural support is the cell wall)- A few prokaryotes, such as the mycoplasmas, have a cell membrane with no outer layers- The cell wall is a single molecule: the bacterial cell wall, or the sacculus, consists of a single interlinked molecule - Why do bacteria have cell walls? The cell wall confers shape and rigidity to the cell, and helps it withstand turgor pressure- With all of the dissolved solutes in a cell, the pressure is about 2


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CU-Boulder EBIO 3400 - Mapping Microbes on the Tree Life

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