Microbiology Midterm Study Guide I Chapter 1 Introduction and History A What is a microorganism i Organism too small to be seen by the human eye ii Size 0 2 5 um long 0 2 um 1 mm wide viruses can be 10x smaller B What is included in the field of microbiology i How microbes live interact reproduce and evolve ii How we identify study grow kill use and benefit from microbes C History Researchers i Anthony van Leeuwenhoek a Found animalcules in drop of lake water b Created magnifying lens to view microbes ii Francesco Redi a Italian priest and physician in late 1600s b Rotting Meat experiment maggots did not grow on meat that was covered c First to disprove spontaneous generation iii Louis Pasteur iv John Tyndall a Swan neck flask experiment broth is sterile but microbes are able to grow in neck of flask when broth encounters microbes they grow in the media b Showed that air is full of microorganisms a Explained discrepancies in swan neck flask experiment not always reproducible b Endospores exist in microbes heat resistant and contain microbe s genome D Spontaneous Generation i ii Disproved by Idea that living organisms can arise from non living organisms a Rotting meat control open flasks that grew maggots b Swan neck flasks iii Endospores in broth weren t killed by heat so they could continue microbial growth this caused discrepancies in repeated studies E Historically important disease epidemics i Smallpox conquests in Americas ii TB widespread in 19th century iii Influenza 1918 pandemic iv Polio diptheria measles pertussis mid 20th century pre vaccinations v Bubonic plague 14th century Europe killed 30 of population vi HIV AIDS late 20th century 21st century F Koch s Postulates i Microbe is found in all cases of the disease but absent from healthy individuals ii Microbe is isolated from diseased individual and grown in pure culture iii Microbe s introduction into healthy host results in same disease iv Same strain of microbe is isolated from newly diseased individual v Used to determine if a strain causes a certain disease G Vaccinations i History a Lady Mary Montagu brought smallpox inoculation to Europe from Turkey in 1717 b Edward Jenner infected patients w cowpox coined vaccination c Pasteur developed first vaccines with attenuated strains of fowl cholera rabies ii Immunization stimulation of immune response by inoculation w attenuated pathogen iii Penicillin a Alexander Fleming 1929 found that penicillium mold helps kill bacteria b first commercial antibiotic saved thousands of lives in WWI iv Selective toxicity ability to only kill pathogenic microbes they target PG cell walls b c only bacteria have them H Microbial benefits i Cyanobacteria for oxygen supply ii nitrogen fixation in plants vital in earth s nitrogen cycle iii decomposition of dead animals plants sewage pollutants iv Food beverage production v Biofuels vi Pharmaceuticals and drugs II Chapter 2 Observing Microbes A Viewing an object i reflection the wave front bounces off the surface of a particle at an angle equal to its incident angle ii refraction when light enters an objects and slows down iii scattering part of the wave front is converted to a spherical wave originating from the object light is scattered in all directions B Types of Microscopy i light use light and magnifying lens to focus on object good for larger objects ii TEM electron beam penetrates thin sample allows you to see internal structure iii SEM scanning 3D surface with electron beam iv Dark field use scattered light to detect objects too small to be resolved by light rays a advantage extremely small microbes and thin structure can be detected b limitation shape of objects isn t well resolved dust can easily obscure image v Cryo EM flash frozen samples are observed material holds its structure vi Atomic force AFM uses IMF measurement to observe cells in water solution C Light Microscopy i magnification increase in apparent size of an image ii resolution smallest distance by which 2 objects can be separated and still distinguished iii refraction see above iv Stains important to add contrast when viewing slides a Simple adds color to just the cell not background or medium methylene blue b Differential colorize one type of cell but not another stains that only color certain structures D Gram Staining differentiates between gram positive and negative cells i Crystal violet stains cells reversibly ii Iodine binds to gram cells to make CVI complex increases stain retention iii Ethanol wash removes crystal violet stain from gram cells iv Safranin counterstains gram cells no effect on gram cells E Cell shapes i Cocci spherical ii Bacilli rod shaped iii Coccobacilli short round rods iv Vibrios curved rods v Spirilli spirals vi Spirochetes helices vii Pleomorphic can vary their shapes F Septation determines the arrangement and shape of coccus cells i Division along a single plane creates pairs diplococci or chains streptococci ii Division along 2 3 perpendicular planes creates cubical packets iii Division along several random planes creates clusters I Chapter 17 Origins and Evolution A Stromatolites are the earliest life form that has clear fossil evidence i Made of calcium carbonate limestone layers created by microbes ii Biofilms of bacteria between the layers iii Inner layers anaerobic sulfate reducing bacteria H2S photolyzing microbes iv Outer layer phototrophic bacteria requiring oxygen B Molecular Phylogeny study of genetic relatedness i Clade an ancestor and all of its descendents phylogeny creates branching clades ii Species in prokaryotes based on DNA relatedness and shared traits ecological niches C How do populations diverge i Random mutations during chromosome replication though most are neutral ii Natural selection favors those that produce more offspring iii Reductive degenerative evolution loss mutation of DNA for traits that aren t needed D Molecular clocks time divergence of species i Shows the random mutations acquired in DNA thru rounds of DNA replication ii Distortion a mutation rate varies among species b varying generation times c alignment errors iii Most consistent measure of time looks at genes encoding trancription translation a rRNA ribosomal proteins tRNA RNA polymerase etc HIGHLY conserved b Most used gene SSU rRNA gene c They have to be correct b c they all interact and disruptions will kill cell d Evolution is slow so changes in these genes are uncommon iv Phylogenetic trees show the frequency of differences in