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Summary of Lectures to For First Exam in Microbiology |
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Origin of Universe – Current Evidence Hubble Expansion - Galaxies appear to be moving away from
our galaxy, initially observed by Edward Hubble in 1927; Galaxies have a red
shift in light produced by the Doppler effect similar to sound (also used in
radar); The movement of galaxies away from us corresponds to an equation
called "Hubble's Law"; The time elements in Hubble's Law permit the
estimation of the age of the universe – about 15 billion years (+ or – a few
billion) Nucleosynthesis Occurred during
seconds 100 to 300 following big bang –Result of
temperature of universe dropping below that required for nuclear fusion (4 H
to He); Produced a large amount of Helium which is very stable and cannot be
converted easily into heavier elements; Amount of Helium measured in universe
is consistent with Big Bang Nucleosynthesis The cosmic microwave background was predicted in 1948 by George Gamow and Ralph Alpher, and by Alpher and Robert
Herman 1964-65Arno Penzias and Robert Woodrow Wilson measure the
temperature to be approximately 3 K. Robert Dicke,
P. J. E. Peebles, P. G. Roll and D. T. Wilkinson interpret this radiation as
a signature of the big bang. Penzias and Wilson received the
1978 Nobel Prize in Physics for their
discovery. Existence of this radiation inconsistent with steady state
model. Origin of Elements Hydrogen fuses to form helium; Hydrogen & Helium most
abundant; Sun’s energy drives life processes; Stars become red giants as
hydrogen runs low (about 10 billion years); Helium fuses into other elements;
Star goes nova (blows up) and heavier elements released into space Origin of Sun and Planets Sun formed about 5 billion years ago from gravitational
attraction of gases; gravitational field becomes great enough to initiate
fusion reactions of hydrogen into helium generating energy; accretion forms
inner planets & moons; process occurs quickly-earth & moon
about same age; takes about 100 million years Early Earth – Current Evidence •Earth 4.6 billion
years old (U238 dating) •Early
Atmosphere mostly non-oxidizing contains Nitrogen Carbon dioxide Water (as
water vapor) and lesser amounts of CO, H2, NH3, H2S
and CH4 Compare to atmospheres of Venus and Mars |
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Characteristics of Life Composed of Cells Reproduce in kind Metabolism / Energy Transformations Respond to stimuli Abiogenesis vs Biogensis The process of life from the inanimate versus life from
preexisting life abiogenesis includes: Formation of organic monomers from inorganic molecules Formation of organic polymers from organic monomers Evolution of membranes Evolution of DNA based reproduction Chemical Evolution Requires a non-oxidizing atmosphere - No oxygen initially Requires a source of energy - Lightening, UV light,
Volcanoes & Meteorites Requires hydrogen, nitrogen, carbon, oxygen –Components of
organic and biological compounds –water, ammonia,
carbon dioxide/methane Requires time Molecular Clues to Origins The following suggest common origin: Organisms use
molecules based mostly on hydrogen, nitrogen and carbon present on early
earth Only L-amino acids found in proteins DNA & RNA are universal
in all organisms ATP is energy intermediate in all organisms All organisms
initiate carbohydrate metabolism with similar steps –Genetic code is universal Organic Monomers Oparin & Haldane
suggest organic molecules could form from precursors (1930) Miller & Urey test using an
apparatus which simulates early earth (~1950) Organic Polymers Major Groups - Nucleic acid, proteins, lipids,
polysaccharides - have been formed synthetically Protenoids
will form spontaneously on clay D & L amino acids can be selected
on calcite - a common crystalline mineral Molecules in living things must have 3 capabilities:
Information vs. Structural vs. Catalytic RNA - has all three
capabilities suggesting first life like capability occurred in RNA RNA “Life” Ribose, a component of RNA will form spontaneously from
formaldehyde and HCN Some RNA’s have been found to have catalytic activity - ribozymes RNA has structural capability in ribosomes RNA’s have an information carrying capacity in viruses
& RNA’s have been induced to take on new traits DNA Life Separation of functional roles of molecules occurs
because molecules more suited to different roles and there is a constant
input of energy Separation of information carrying capacity from other roles
of molecules in cells RNA to DNA RNA to Protein - catalytic capacity Protein & polysacharides
take on structural roles in cells Membranes Why cells? Inside vs. outside Concentration effect on reactions Indications of process Microspheres - hydrocarbons in
water form microsperes which can contain other
molecules Liposomes - artificial lipid bilayers very similar to cell membranes but smaller -
used for drug transport Prokaryotic Cells Appear about 3.5 billion years ago Photosynthesis in blue-green algae begins to modify
atmosphere Oxygen in atmosphere begins to modify types of organisms Eukaryotic Cells Begin to appear in fossil record about 2.5 billion years
ago Considerable internal structure relative to prokaryotic
cells Precursors to multicellular
organisms Fossil Record Dating –Stratographic analysis –Radiometric dating Geologic Time –Precambrian - 4.6 to 0.57 billion years ago Fossils all unicellular –Caambrian – 0.57 billion years
ago to present •Multicellular
organisms •Extinction Level
Events Evidence for Evolution Physical methods – radiometric dating Fossil record Anatomical comparisons DNA sequence analysis Laboratory experiments showing selection |
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Microscopy History Compound Light Microscopes Types of Microscopy Measurement Systems Measuring in a Microscope Staining Procedures Early History of Devices that Alter Light: –Claudius
Ptolemy (2nd Century B.C.) »Described
refraction water –Seneca
(1st Century A.D.) »Described
magnification by a globe of water –Alhazen (962-1038 A.D.) »Described
optical principles & anatomy of eye –Roger
Bacon (1267 A.D.) »Described
simple magnification Lenses derived need to improve eyesight –Pliny
the Elder wrote of Nero’s use of emeralds to watch gladiators –Reinvention
of spectacles occurred around 1280 to 1285 in –Dutch
spectacle maker Zaccharias Jansen was probably
first to combine two lenses into compound microscope (1595) Robert Hooke (1665) –Contemporary
of Robert Boyle; Described cork with “cells” – first use of “cell” to
describe structure of living organism; made & used a compound microscope Antoni van Leeuwenhoek Made his own simple single lens microscopes; First to
describe bacteria, blood, protozoa & sperm; sent letters & drawings
to Royal Society Problems with early microscopes Chromatic aberration Occurs when different wavelengths of
light are refracted through the lenses at different angles; Corrected using
glass of different types Spherical aberration - Distortion because light hitting
edge of lens does not have same focal length as middle corrected using small
apertures or diaphragms; Solved by Joseph Jackson Lister in 1830 Microscope parts –Ocular –Objectives –Stage –Diaphragm –Condenser –Light
Source –Course
adjustment –Fine
adjustment Modern compound microscope –Diaphragm –Condenser –Oil
Immersion Compound Microscope –Total
Magnification »Ocular
X Objective equals Total –Refractive
Index »A
measure of the relative velocity of light passing through a substance –Oil
immersion »prevents
light scattering between slide and objective – has same refractive index as
slide Compound Microscope – Resolution –The
ability of a lens to distinguish between two points as separate objects –Depends
on wavelength of light – usually maximum resolution is wavelength / 2 –Maximum
for light microscope is about 0.2 microns or about 2000x Types of Modern Microscopy –Bright
field –Dark
field –Phase
Contrast –Electron
Microscopy –Scanning
Electron Microscopy –Fluorescent
(UV) Measurement (Metric System) –Meter
(m) 100 –Centimeter
(cm) 10-2 –Millimeter
(mm) 10-3 –Micrometer
(µm) 10-6 –Nanometer
(nm) 10-9 Staining Techniques Preparation Smear Heat Fixation Stain/counter stainNegative stain Simple stains Crystal violet Saffron Methylene
blue Mordant Intensifies stain Iodine used in Gram stain Differential Stains Stain one group of
organisms/cells different than another; includes Gram stain Acid Fast
Stain Special Stains Capsule Endospore
Flagella |
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History of Microbiology Science is systematized knowledge developed through the
application of the scientific method; Scientific method includes: –Observations
(objective vs. subjective) –Formulate
hypothesis –Test hypothesis
with controlled experiments –Accept, revise or
reject hypothesis Early Observations & Experiments in Microbiology Microscopes –van Leeuwenhoek
& Hooke Spontaneous Generation Controversy •Germ Theory of
Disease & Robert Koch Spontaneous Generation Biogenesis vs. Abiogenesis Biogenesis - development of life from preceding life forms Abiogenesis - life arises from
inorganic or non-living materials Jan Baptista van Helmont Reported in late 1500’s that barley grains and old shirts
left in a corner would spontaneously give rise to mice; Claimed as evidence
that supported spontaneous generation or abiogenesis Francisco Redi (1626-1697) Set up controlled experiment to test idea of spontaneous
generation with respect to maggots appearing on rotting meat: open jar with meat;
screened jar with meat sealed jar with meat John T. Needham (1713-1781) Flies do not arise spontaneously but the “animalcules”
described by van Leeuwenhoek must; In 1748 Needham boiled mutton broth, stoppered and noted that flask became turbid; Argued that
the turbidity, which included many “animalcules” must have arisen
spontaneously Lazzaro Spallanzani
(1729-1799) Repeated Theodor Schwann
(1810-1882) An argument against Spallanzani
experiments is that they excluded air; Constructed apparatus to sterilize air
coming into flask; Results supported biogenesis Louis Pasteur (1822-1895) Looked at air which had been filtered; Developed swan neck
flask to deal with heated air problem; Looked at frequency of occurrence of
contaminated flasks; Settled controversy Performed a large number of experiments under a variety of
conditions Germ Theory of Disease Observation on causative agents of potato blight and
diseases of silkworms led to hypothesis Formalized through work of Pasteur and Koch (and others)
led to theory that germs or microorganisms may cause disease Germ Theory of Disease Robert Koch first developed relationship between
microorganisms and disease Developed Koch’s Postulates for testing relationship Discovered cause of anthrax and tuberculosis Koch’s Postulates: –Same microorganism
must be observed in every instance of disease –Organism must be
isolated from diseased host and grown in pure culture –Specific disease
must be reproduced when pure culture is reintroduced into host |
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History of Cells –Robert
Hooke (1600’s) first described cells in thin
sections of cork that he examined under microscope –Robert
Brown (1820) first to describe that a nucleus seemed to be associated with
all cells (at least eukaryotic cells) –Theodore
Schwann & Matthias Schleiden
(1839) advanced cell theory »All
organisms are composed of cells »The cell
is the basic unit of life »All cells
arise from preexisting cells Cells Cell Types Prokaryotic(beginning cells and eukaryotic
(true cells) Sizes Prokaryotic (0.2 to 2.0 microns) Eukaryotic
( 10 to 100
microns
0 Size Determinants of Cells –Cell
surface to volume relationships govern cell size –The
smaller the cell the more efficiently materials can be transported into the
cell –Cell
must also be large enough to deal with information and metabolic requirements Common Components to All Cells –Plasma
membrane – phospholipid bilayer
that controls movement of substances into and out of cells –Ribosomes – site of protein synthesis –Cytoplasm
–matrix on interior of cell consisting of water soluble proteins and other
materials –Nuclear
material – DNA/Protein complex that stores information »Prokaryotic
– circular »Eukaryotic
– linear and in chromosomes Eukaryotic Cells Larger than prokaryotic More complex than prokaryotic All multicellular organisms composed of eukaryotic cells
Eukaryotic cells composed of many internal structures called organelles Structures in Eukaryotic cells lNucleus Regulates growth and reproduction of cell; Contains DNA
and chromosomes lNucleolus
Ribosomal RNA synthesis lMitochondria
Energy production in cell; Contains its own DNA (circular) lEndoplasmic
reticulum (rough and smooth) Site of protein synthesis in cells; Start of protein
export process; Connected to nuclear pores and Golgi
body lGolgi body Sorting center for proteins in cell; Produces vesicles
which fuse with plasma membrane lLysosome Only in animal cells; Production of intracellular
digestive enzymes; Involved with phagocytosis lPeroxisomes Peroxisomes are small rounded
organelles found free floating in the cell cytoplasm; Contain at least 50
enzymes and are separated from the cytoplasm by a lipid bilayer
single membrane barrier; Produce hydrogen peroxide which is toxic but is
rapidly degraded by catalase lFlagella
& cilia Involved with motility of cells; Composed of microtubules lVacuoles Found only in plants Large central organelle in plant
cells; Regulates water in plant cells lChloroplast Site of photosynthesis in plant cells; Has own DNA
(circular); Found only in plants Prokaryotic Cells Morphology & Specialized Structures & Ultrastructure Size, Shape & Arrangement of Prokaryotic Cells 0.2 µm to 2.0 µm diameter 2 µm to 8 µm in length Three basic shapes cocci (spheres) bacillus (rods) spirochete (twisted/spiral) Pleomorphic shapes Characteristics of Prokaryotic Cells Smaller than eukaryotic cells No nuclei or chromosomes No membrane-bound internal organelles Circular genomic DNA 70S Ribosomes Cell division by binary fission No meiosis; recombination by transfer of DNA fragments Shapes of Prokaryotic Cells Cocci spheres Staphylo- clusters; Strepto-
chains; Bacilli rods Spirochete spirals Specialized Structures Endospores – a structure produce
primarily by Clostridia and Bacillus species to resist desication Acid Fast Bacteria – a waxy sheet or coat produced by Mycobacteria Club shape – produced by Corneybacteria Prokaryotic cells external structures Flagella Long filamentous protein; filament; hook;
basal body –Rotates
to propel cell in response to taxis (positive and negative) Capsules Slime layer Polysaccharide or polypeptide
Protection from phagocytosis by host; gives cells
“Stickiness” permits adherence also prevents desiccation Cell Envelope or Cell Wall –Gram
positive Peptidoglycan (Multi layer) Teichoic acid –Gram
negative Peptidoglycan (single layer) Outer
membrane (lipopolysaccharide) Primary function is
resist changes in osmotic pressure; also functions in recognition Peptidoglycan composed of
polysaccharide of alternating N-acetylglucosamine
& N-acetylmuramic acid; Peptide composed of D-
and L- amino acids Lipopolysaccharide of gram negative
cells in outer membrane of Gram negative cells & composed of lipid and
carbohydrate; Carbohydrate referred to as O-antigen; Associated with some endotoxins in pathogenic G- bacteria Teichoic Acid - sugar alcohol
plus phosphate found only in Gram positive cell walls Fimbriae associated with the
adhesiveness of cells to surfaces Pili involved in the transfer of
genetic material |
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Plasma Membrane Basic molecular components of membrane Phospholipids Membrane proteins Membranes must be fluid Fluid Mosaic Model Phospholipid bilayer
Formed by association of hydrophobic tails Polar (hydrophillic) groups form
inside and outside of membrane Membrane Proteins Proteins are integral or peripheral Proteins involved in plasma membrane functions Membrane must be fluid to function Components are free (to a degree) to move across surface Functions Boundary between inside and outside Recognition Energy (respiration and photosynthesis) Selective permeability of materials Transport Processes Across Membranes Diffusion Active transport Bulk transport Diffusion Processes Simple Diffusion – movement of small uncharged molecules Osmosis – special case of diffusion; diffusion of water in
response to solute concentration Facilitated Diffusion – diffusion using a channel protein Diffusion – the movement of molecules from area of high
concentration to low concentration Osmosis Isotonic Solute concentration same on both sides of plasma membrane Hypotonic Hypo- below Solute concentration less outside cell than inside cell Hypertonic Hyper- above Solute concentration greater outside cell than inside Facilitated Diffusion Diffusion that occurs through use of a channel protein Active Transport Movement against energy concentration gradient Requires energy; usually in form of ATP Bulk transport – An active transport process Eukaryotic cells only Endocytosis Pinocytosis Phagocytosis Exocytosis & secretory processes |
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