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Pathogen
an infecting microorganism able to cause disease
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General uses for microorganisms
- biotechnology- manipulate microorganisms to make products to in an industrial setting
- recombinant DNA technology- potential in terms of medical, industrial, and agricultural uses
- bioremediation- introduction of microbes into the environment to restore stability or to clean up toxic pollutants
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Biogenesis and abiogenesis
- biogenesis- living organisms arise only from others of their same kind (cells could only come from other cells, the cell was the simplest component of an organism)
- abiogenesis (spontaneous generation)- belief that living organisms arose from vital forces present in nonliving and decomposing matter
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Leeuwenhoek, Antonie Van
1673- reports the 1st observation of bacteria and protozoans
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Redi, Francesco
- (biogenesis)
- 1670's- 1st to disprove spontaneous generation
- Left out jars of rotting meat, some were sealed and others were not
- Meat in the jars exposed to the air developed maggots. Those covered did not
- Scientists concluded that killing the microorganisms that caused disease could prevent the disease from occurring (proved biogenesis law correct)
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Jablot, Louis
- (biogenesis)
- 1748- did hay infusion experiment
- boiled hay & water & put in jar; no microbes
- unboiled hay & water in jar; got microbes
- infusion lacked endospores
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Needham, John
- (abiogenesis)
- experiment on mutton gravy
- microbes still grew in the gravy flasks
- done before the realization that heat resistant microbes are not killed by mere boiling.
- microbes in the gravy produced endospores
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Spallanzani, Lorenzo
- (biogenesis)
- Repeated Needham’s experiment, but he boiled the meat broth longer than Needham. The sealed flask did not become cloudy with microorganisms, but the open flask did.
- 1. Needham had either failed to heat his vials sufficiently to kill all microbes
- 2. Microorganisms exist in the air and contaminate all experiments
- 3. Spontaneous generation of microorganisms does not occur; all living arise from other living
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Pasteur, Louis
- (biogenesis)
- 1857- refined the process of fermentatio
- propesed the germ theory of disease which states that microorganisms cause infectious disease
- 1861- last to disprove the doctrine of spontaneous generation
- experimented with boiling beef broth ( airbone organisms contaminated open flasks)
- used swan necked jars
- 1864- discovered the process of pasteurization which is one of the best known sterilization techniques
- 1855- introduced the vaccines against rabies and anthrax
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Lister, Joseph
- 1867- introduced aseptic techniques
- surgeons to use phenol to wash and disinfect their hands before surgery
- disinfection of wounds with phenol
- supported the germ theory of disease
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Koch, Robert
- studied Anthrax bacterium and its transmission in animals
- 1876- verified germ theory of disease with Koch's postulates
- 1881- introduced techniques for pure cultures introducing solid culture medium
- 1882- discovered M. tuberculosis
- 1905- won Nobel Prize in Medicine/ Physiology
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Koch's Postulate's-
- Postulate #1: the same microorganism must be present in every case of the disease
- Postulate #2: the organism should be isolated from the tissues of the infected animal and grown in a pure culture
- Postulate #3: the organism from the pure culture is inoculated into a healthy animal and the same disease should be produced
- Postulate #4: the pathogen must be isolated from the experimental animal and shown to be the original organism
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Fleming, Alexander
- 1928- discovered penicillin (growing bacteria in media)
- Penicllin notatum, at one time, killed Staphylococcus aureus, leading cause of infection
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Disproved abiogenesis?
- 1. Redi (first 1670's)
- 2. Jablot
- 3. Spallanzani
- 4. Pasteur (last, 1861)
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Disease through time
- 60's "time to close the book on infectious disease" (Luther Terry, 1964)
- 90's "infectious diseases a rising peril- up 58% since 1980" (David Satcher, 1998)
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Causes of Disease
infectious diseases most common death in much of fumanity
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Prokaryotic Cells
- no nucleus is visable (single circular chromosome) (nucleoid)
- lack membrane bound organelles
- have cell walls that generally consist of peptidoglycan
- divide by binary fission
- appendages
- motility
- cell envolope
- cell wall
- gram staining
- no mitochondria
- plasmids
- ribosomes
- bacterial endospores
- fimbriae and pili
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Eukaryotic cell
- nucleus
- membrane bound organelles
- no cell wall
- have mitochondria
- the chromatin is associated with histone proteins
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Prokaryotic Appendages and types
- Flagella (propellers)- motility
- 1. Monotrichous- 1 flagella
- 2. Amphitrichous- flagella on both sides
- 3. Lophotrichous- tuft of flagella
- 4. Peritrichous- around the cell
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Prokaryotic Appendages and Motion
- Polar flagellum rotates:
- counterclockwise---> swim forward
- clockwise--> stops and tumbles
- Petrichous flagella:
- all flagella sweep toward one end of the cell and rotate as a single group ---> forward
- flagella rotate in the opposite direction cause the cell to lose cordination--> tumbles
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Periplasmic flagella
- internal flagella
- between the cell wall and cell membrane and spirals around the cell
- aka axial filaments or endoflagella
- present in bacteria known as spirochetes:
- 1. Treponema pallidum
- 2. Borrelia burgdorferi
- curl, free to contract and allow the cell to twist and flex
- Spirochetes
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Cell Envelope (layers)
- the outer wrapping of bacteria
- 3 layers:
- 1. Glycocalyx
- 2. Cell Wall
- 3. Cell Membrane
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Glycocalyx
- outermost coating of bacterial cells
- subcategories:
- 1. Slime layer
- 2. Capsule
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Slime layer
- part of glycocalyx sublayer of bacterial cells
- loose and disorganized layer of macromolecules
- for attachment
- white plaque formed by surface slimes
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Capsule
- part of glycocalyx sublayer of bacterial cells
- formed by:
- 1. Stephtococcus pneumonia
- 2. Haemophillus influenzae
- 3. Bacillus anthrax
- 4. Streptococcus mutans
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Staining for Capsules
- Negative stains are used to reveal the presence of negatively charged bacterial capsules.
- Encapsulated cells appear to have a
- halo around them.
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Cell Wall
- second layer of the cell envelope of a bacterial cell
- consits mainly of a macromolecule called peptidoglycan , peptides, lipoproteins and lipopolysaccharides
- give bacteria their characteristic shape and structural support
- Most bacteria to live, or capable of living in hypotonic environments. Their cell walls protect them from bursting from the increased osmotic pressure.
- Hypertonic solutions inhibit or kill bacteria
- Two types of cell walls:
- 1. gram (+) cell walls
- 2. gram (-) cell walls
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Gram (+) cell walls
- stain purple
- lack outer membrane
- larger peptidoglycan layers (20-80nm)
- high PG content--> allows to retain dye
- stain purple
- the many layers of peptidoglycan are resistant to alcohol, therefore, it will stain purple
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Gram (-) cell walls
- stain red
- have an outer membrane (lipopolysaccharides)
- thin layer of peptidoglycan
- the alcohol dissolves lipids in the outer membrane and removes dye
- because the gram(-) bacteria are colorless, the red dye adheres to the cell
- may prevent the movement of penicillin to the underlying peptidoglycan, impeditive to the treatment of disease
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Atypical cell walls
- 1. Mycobacterium and Nacardia
- contain peptidoglycan and stain gram (+)
- composed of mycolic acid (fatty acid chain)
- not found on gram stain
- found by Ziehl-Neelsen stain
- 2. Acid fast stains
- 3. Archae
- 4. Mycoplasmas
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L forms
- have a cell wall but may have lost it due to :
- mutations in the wall forming genes
- treatment with lysozyme or penicillin that disrupts the cell wall
- L forms are associated with some chronic infections
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The Cell membrane (bacteria)
- innemost layer of the cell envelope
- phospholipid bilayer
- functions:
- site where energy reactions take place (cellular or anaerobic respiration, donate and accept e-)
- selectively permeable
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Plasmids
- small pieces of DNA (1-4 genes)
- plasmids acquired from other bacteria allow cells to grow fimbriae (hair-like structures sprouting off some bacterial cells for attachment) and capsules
- may allow a cell to become resistant to anitbiotics
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Mesosome
- extension of the cell membrane that folds into the cytoplasm and increases surface area
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Pilus
- elongate, hollow appendage used in transfers of DNA to other cells and in cell adhesion
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Inclusion Granules
- "inclusion bodies" extra food
- store bodies
- Metachromatic granules: contain inorganic phosphate reserves (nucleic acids)
- Polysaccharide granules: glycogen and starch
- Lipid and sulfer inclusions
- inorganic compounds and are not bound by membranes
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Bacterial Endospores
- resting cells or dormant bodies
- by gram (+) genera
- Bacillus and Clostridium
- these cause anthrax, tetanus, and gangrene
- are dehydrated and have a very thick cell wall rich in dipicolinic acid, which makes them extremely hard to destroy
- can resist for extremely long periods of:
- 1. Drying
- 2. Freezing
- 3. Radiation
- 4. Chemicals
- 5. Alcohols
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1. Sporulation or sporogenesis (spores)
2. Germination
- triggered by depletion of nutrients
- triggered by water, favorable conditions, and the presence of a germination agent (an amino acid or an inorganic salt)
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Saffer-Fulton Endospore stain
- uses heat to drive the primary stain
- malachite green (spore)
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Organisms that contain SPORES
- 1. Bacillus anthrax (Anthrax)
- 2. Clostridium tetani (Tetanus)
- 3. Clostridium botulinum (Botulism)
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Colonial Morphology
- 1. Gram
- 2. Shape
- 3. Arrangement
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Bacterial Shapes
- 1. Coccus
- 2. Bacilli
- 3. Spirilla
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Coccus
spheres, oval shaped, kidney or bean-shaped, or slightly pointed
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Coccus Arrangements
- 1. Diplococci
- 2. Tetrads
- 3. Steptococci (chains)
- 4. Staphylococci (clusters)
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Bacillus
rod shaped or cylindrical
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Bacillus Arrangements
- 1. Bacilli
- 2. Coccobacillus
- 3. Diplobacilli
- 4. Palisades
- 5. Streptobacilli
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Vibrio
- curved rods
- polar flagella
- Cholerae
- gram (-)
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Spirochetes
- type of spiral bacteria; helical and flexible; move by means of axial filaments
- (resemble flagella but are contained within a flexible external sheath)
- syphilis and Lyme
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Viruses
- DNA or RNA (nucleic acid)
- genetic material is surrounded by a protein coat (caspid)
- not a complete cell
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Fungi
- made out of hyphae (filaments)
- exist in two forms:
- 1. Yeast: single celled organisms
- 2. Molds: when they produce long, tubular, branching filaments known as hyphae
- ability to switch from the hyphal cells typical of molds to yeast cells typical of the parasitic phase (thermal dimorphism)
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Protozoans
unicellular eukaryotic cells that contain specialized structures for feeding movement and reproduction
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Helminths (worms)
- Eukaryotic, multicellular organims (animals)
- 0.3mm to tapeworms over 20 ft long
- 3 main groups:
- 1. Nematodes (roundworms)
- 2. Cestodes (tapeworms)
- 3. Trematodes (flukes)
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Helminths (1. Nematodes)
- Nematodes (roundworms)
- cylindrical with cuticles
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Helminths (2. Cestodes )
- Cestodes (tapeworms)
- have long ribbon like bodies composed of proglottids and a scolex
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Helminths (3. Trematodes)
- Trematodes (flukes)
- flatworms with leaf like bodies bearing suckers
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