Koch s postulates How to test the hypothesis INFECTIOUS AGENT X CAUSES DISEASE Y Infectious agent X must meet four criteria 1 Agent X must always be present in host s with disease Y and absent in those that do not have disease Y 2 Must be able to isolate pure culture of agent X Introduction of agent X into a new host induces disease Y 3 4 Agent X can now be re isolated from this new diseased host 1876 Robert Koch proved that a bacterium causes anthrax and provided the experimental steps Koch s postulates to prove that a specific microbe causes a specific disease Be able to convert distances between nanometers nm micrometers um and millimeters mm you can use a calculator for this but it must not be an app in your phone It must be a calculator that does not have networking capability You may not need a calculator the conversions will all be just moving the decimal point based on the conversion factor 1 millimeter 10 3 meter 1 micrometer or micron 10 6 meter 1 nanometer 10 9 meter 1 angstrom 10 10 meter 1 picometer 10 12 meter 1000 nanometer 1 micrometer Know what Pasteur disproved In 1861 Pasteur s experiment involving the S shaped flask kept microbes out but let air Pasteur demonstrated the microorganisms are present in the air in They contaminate the broth when the flask is open and they fall in This disproved spontaneous generation of microbes Spontaneous generation is the hypothesis that living organisms arise from nonliving matter Know the details of the discovery of penicillin In 1928 Alexander Fleming discovered the first antibiotic He observed that Penicillium fungus made an antibiotic Penicillium that killed Staphylococcus aureus In the 1940s Penicillin was tested and clinically and mass produced Know the causes of the emerging infectious diseases we covered in Lecture 2 and know the Saves lives during World War II MRSA is resistant to penicillin background we discussed on these infectious agents Spanish Flu Caused by the Influenza Virus Killed 40 50 million people worldwide Largest loss of population in history Avian Flu Caused by the Influenza A virus Primarily in waterfowl and poultry Severe Acute Respiratory Syndrome SARS Associated with Coronavirus Person to person transmission Ebola Hemorrhagic Fever Ebola Virus First identified near Ebola River Congo Seems to come from bats West Nile Virus A viral emerging infectious disease Causes encephalitis Carried by birds First diagnosed in the West Nile regions of Uganda in 1937 Bovine Spongiform Encephalopathy Mad Cow Disease Caused by a Prion Prions are not alive Escherichia coli O157 H7 A prion is a misfolded protein that can cause other proteins to misfold by contact A bacterial emerging infectious diseases A strain of Enterohemmorhagic E coli EHEC Toxin producing strain of E coli Animals can serve as a reservoir Cows are asymptomatic carriers Invasive Group A Streptococcus Streptococcus pyogenes A bacterial emerging infectious disease Can damage huge amounts of tissue Clostridium difficile A bacterial emerging infectious disease Often acquired in a health care setting This is called a nosocomial infection Methicillin resistant Staphylococcus aureus MRSA A bacterial emerging infectious disease Acquired resistance to multiple antibiotics 1950s Penicillin to multiple developed 1980s Methicillin resistance 1990s MRSA also resistant to vancomycin VISA vancomycin intermediate resistant S aureus VRSA vancomycin resistant S aureus Cryptosporidiosis Caused by the Cryptosporidium protozoan Most commonly transmitted via contaminated water and food Know the composition of an E coli cell by weight for the major classes of macromolecules we discussed Water 70 Inorganic Ions 1 Small molecules 1 Carbohydrates 3 Lipids fats 2 Proteins 15 Nucleic Acid DNA 1 RNA tRNA 1 RNA rRNA 5 RNA mRNA 0 06 Know the approximate size range of bacteria viruses etc and which types of microscopy are useful for each Yeast s approximate size is 10 micron Light Microscopy can be used to magnify yeasts Bacteria s length 0 5 10 micron Some bacteria can be magnified with Light Microscopy and Scanning Electron Microscopy can also be used to see some bacteria Viruses length 20 300nm Transmission electron microscopy is used to magnify viruses Be able to define magnification resolution diffraction Magnification The total magnification of a specimen is the objective lens magnification multiplied by the ocular lens magnification Resolution also called resolving power Is the ability of the lenses to distinguish fine detail and structure For a light microscope is this usually about 200 nm part 0 2 micron Shorter wavelengths of light provide greater resolution Diffraction Know the major types of microscopy we discussed What type of beam is used etc Dark Field Microscopy Image is formed by light scattered or refracted by a specimen Produces a bright image of the object against a dark background Phase Contrast Microscopy Accentuates diffraction of the light that passes through a specimen Uses one beam of light refractive index Enhances the contrast between intracellular structures having a slight differences in Differential Interference Contrast Microscopy Accentuates diffraction of the light that passes through a specimen Uses two beams of light Fluorescence Microscopy Uses UV to fluorescent spectrum of light Fluorescent substances are excited by one wavelength of light emit of a longer wavelength and lower energy Cells may be stained with fluorescent dyes called fluorochromes or fluorphores Confocal Microscopy wavelength Uses a laser light to excite fluorochrome causing it to emit light at a longer The laser illuminates each plane in a specimen to produce a three dimensional image Two Photon Microscopy Two photons of long wavelength red light are used to excite the dyes Used to study cells attached to a surface Scanning Acoustic Microscopy Measures sound waves that are reflected back from an object Used to study cells attached to a surface Electron Microscopy Uses electrons instead of light The shorter wavelength of electrons gives greater resolution Transmission Electron Microscopy Light passes through the specimen than an electromagnetic lens to a screen or film Ultrathin sections of specimens Scanning Electron Microscopy An electron gun produces a beam of electrons that scans the surface of a whole specimen Secondary electrons emitted from the specimen produce the image Scanned Probe Microscopy Uses a metal and diamond probe inserted into the specimen Produces three
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