MMG301 1nd EditionExam # 1 Study Guide Lectures: 1 - 9Lecture 1 -see syllabus-microorganisms-organisms only seen under a microscope-range in size from .2 micrometers to a few millimeters-prokaryotes: bacteria and archaea-eukaryotes: algae, fungi, protists, plants, animals-first discovery of microbes in the 17th century-Robert Hooke (1660s)-first compound microscope-described eukaryotic microorganisms-described fruiting structures on fungi-named the “cell” as a unit of living material-Antoni van Leeuwenhoek (1680s)-simple microscopes with 300x magnification-first to describe bacteria-bacteria of various shapes and motility in different environments-Theory of spontaneous generation: thought of in 320 BC by Aristotle; states that life arises frominanimate objects-the defeat of the theory of spontaneous generation-Francesco Redi (17th century): experiments with maggots-Lazzaro Spallanzani (18th century): found that a boiled medium in a sealed flask does notputrefy-Louis Pasteur (1860s): ended the theory of spontaneous generation by showing that heated food exposed to air does not putrefy using the “swan neck” flask experiment-Pasteur also found that yeasts produce beer, discovered pasteurization as a method to stop milk from spoiling and causing sickness, and made the first vaccines for chicken cholera and rabies-germ theory of disease: Ignaz Semmelweiz; explained the transmission of puerperal fever; stated that microorganisms are the cause of many diseases-Robert Koch: provided additional evidence to support the germ theory of disease-Koch’s Postulates: set the experimental criteria required to link the presence of a microbial pathogen to the disease it causes -great discoveries of the 19th century-Theobald Smith: ticks transmit an infectious disease to mammals (Texas cattle fever)-Ferdinand Cohn: heat-resistant endospores; foundation for bacterial classification system-Petri: transparent plates to cultivate and view bacteriaLecture 2-microscopes-light microscope: uses glass lenses; maximum resolution 0.2 micrometers-electron microscope: uses electromagnets; maximum resolution 0.2 nanometers-interaction of light with matter-transmission: light goes through without being altered-absorption: object absorbs part of the light; energy level in the object increased-reflection: light bounces off the surface-refraction: light bends when it enters an object that alters its speed-scattering: some of the light is scattered in all directions-bright field microscope: the image results from light transmission through the sample and light absorption by some cell constituents-poor contrast-oil immersion lense increases resolving power-dark field microscopy: shows bright objects against a dark background-good for very thin or small specimens-phase contrast microscopy: provides increased contrast between bacteria and viewing medium-ideal to examine cell morphology-fluorescence microscopy: fluorescent cell appear colored against a dark background-staining techniques (to improve contrast)-simple stain: single stain, all objects are the same color-differential stain: multiple stains to distinguish between organisms-gram stain: allows detection of bacteria associated with host cells-positive: purple-negative: pink-acid-fast stain: differentiates mycobacteria from other bacteria-electron microscopy: uses an electron beam and magnets-used to study cell ultrastructures-transmission electron microscopy: sample is embedded in a polymer thin-section stain with heavy metal salts-shows external coats, cell envelope, internal structures, cell surface texture, and very thin external appendagesLecture 3-facts about microbial diversity and abundance-microbes outnumber all other species and make up ~60% of the earth’s biomass-microbes drive the chemistry of life and affect the global climate -microbial cycling of chemical elements helps keep the world inhabitable-microbes generate at least half the oxygen we breathe -microbes thrive in extreme environments-500 to 1,000 species of bacteria live in the human gut-there are at least 10 times more bacteria as human cells in the body-less than 0.5% of the estimated 2-3 billion microbial species have been identified-physiologic diversity of microorganisms-chemotrophs-chemoorganotrophs: organic molecules-chemolithotrophs: inorganic chemicals-phototrophs-anoxygenic: do not produce oxygen-oxygenic: produce oxygen-carbon-autotrophs: use CO2 as a sole source of carbon-heterotrophs: use preformed organic carbon molecules as carbon source-oxygen-strict aerobes: only grow in the presence of O2-strict anaerobes: only grow in the absence of O2-facultative anaerobes: can grow in the presence or absence of O2-evidence for microbial life on early earth-isotopic carbon ratios-stromatolites: fossilized microbial malts-microbial fossils in ancient rocks-subsurface hypothesis for the origin of life-life arose in hot, oxygen free environment-most likely on the ocean floor-evidence: present day hyperthermophiles in deep sea ventsLecture 4-phylogeny: the evolutionary history of a group of organisms-it is inferred from DNA sequence data-changes in DNA sequence are inherited by descendants-building phylogenetic trees from 16s rRNA (ribosomal RNA) sequences-first step: obtain the sequence of the 16s rRNA gene-second step: align the sequences-third step: build the phylogenetic tree-phylogenetic trees: -convey the implied evolutionary relationship-common approaches to building tree-maximum parsimony: the fewest mutations to fit the data-maximum likelihood: highest probability-node: point at which branches split-rooted: has known starting point-unrooted: starting point is unknown-taxonomy: science of classification of life forms-core activities-1. Classification-2. Nomenclature-3. Identification-classification methods-1. Traditional, artificial: based on phenotype (observable characteristics)-2. Modern, phylogenetic: based on genotype (evolutionary relationships)Lecture 5-major energy yielding processes in biology (all use oxidation-reduction processes)-1. Fermentation-electron donor: growth substrate (organic compound)-electron acceptor: organic molecule produced by the cell-ATP production: substrate level phosphorylation-does no consume oxygen-2. Respiration-electron donor: organic or inorganic compound-electron acceptor: exogenous (outside the cell) organic or inorganic compound-ATP production: proton motive force-3. Photosynthesis-electron donor: H20 (if oxygenic), another
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