Download Topic 1: Introduction

Topic 1: Introduction
How microbiology integrates into your course of study:
 Food processing to minimize disease
 Crossover between health and agriculture
 Industrial fermentation, producing foodstuffs, pharmaceuticals, etc.
Several ways in which microbes affect our lives:
 Microorganisms are too small to be seen with the unaided eye
 Micro=small, bios=life and ology=study
 A few microbes are pathogenic
 Some fungi decompose organic waste or fix nitrogen (bacteria)
 Produce industrial chemicals like ethanol
 Produce fermented food
 Some make recombinant vaccines and pharmaceuticals
Know the correct taxonomic hierarchy:
 Domain, Kingdom, Phylum, Class, Order, Genus, Species
 Dumb Kids Playing Chicken On Freeways Get Squashed
 Scientific names avoid confusion with common names
 System devised by Carolus Linnaeus
 Scientific name has two parts: Genus (eg, Escherichia) and specific epithet (eg, coli)
 Together they make the scientific name
Name the types of microorganisms and their characteristics:
 Bacteria, Archaea, Fungi, Protozoa, Algae, Multicellular animal parasites and Viruses
 Baceria and Archaea are prokaryotes, the following four are eukaryotes and viruses are
acellular
 Bacteria are prokaryotic, usually contain a peptidoglycan cell wall, reproduce with binary
fission and use inorganic energy sources
 Archaea are prokaryotic, lack peptidoglycan, live in extreme environments and include
methanogens and extreme halophiles and thermophiles
 Fungi are eukaryotic with chitin cell walls, use organic energy sources, are multicellular
consisting of masses of mycelia, composed of filaments called hyphae, yeasts are unicellular
 Protozoa are eukaryotic, absorb or ingest organic chemicals, can be motile via pseudopods,
cilia or flagella
 Algae are eukaryotic with cellulose walls, use photosynthesis for energy and produce
molecular oxygen and organic compounds
 Multicellular animal parasites are eukaryotic, include parasitic flatworms and roundworms
called helminths and all have microscopic life cycle stages
 Viruses are acellular and consist of DNA/RNA core surrounded by protein coat which may be
enclosed in a lipid envelope, viruses are replicated only when they are in a living host cell
List the three domains of life:
 Three domains: Bacteria, Archaea and Eukarya
 Eukarya include protists, fungi, plants and animals and us
 System was devised by Carl Woese
Key contributors to microbiology history:
 Robert Hooke coined the term ‘cells’ to describe cork cells, beginning of the cell theory
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Anton van Leeuwenhoek observed the first microbes and constructed microscopes, first to
see protozoa and bacteria
Carolus Linnaeus devised taxonomy system
Edward Jenner produced the first vaccine against smallpox
Agostino Bassi de Lodi showed that silkworm disease was caused by a fungi
Ignaz Semmelweiss demonstrated that hospitals spread childbed fever when delivering and
introduced hand washing
Louis Pasteur discovered fermentation, disproved spontaneous generation and invented
pasteurization
Robert Virchow introduced the concept of biogenesis
Joseph Lister introduced antiseptics in surgery, convinced by the germ theory of disease
Robert Koch cultivated anthrax bacteria outside the body in serum and devised Koch’s
postulates for microorganisms in disease
Paul Erlich discovered salvarsan to combat syphilis, ‘magic bullet’ chemical to kill bacteria
Alexander Fleming discovered Penicillin which can kill bacteria
Compare spontaneous generation and biogenesis:
 Spontaneous generation is the hypothesis that living organisms arise from non-living matter
 Biogenesis is the theory that living organisms arise from pre-existing life
 Francesco Redi filled six jars with meat and covered half of them, and only the uncovered
ones grew maggots
 John Needham put boiled nutrient broth into covered flasks, and microbial growth appeared
 Lazzaro Spallanzani put boiled nutrient solution in covered flasks and boiled it and no
microbial growth appeared
 Louis Pasteur placed nutrient broth in flasks, heated and not sealed one, and heated then
sealed the other. Microbial growth appeared in the first, but not the second
 Pasteur was repeatedly able to demonstrate this and spontaneous generation was
abandoned
Define…:
 Bacteriology: the study of bacteria
 Mycology is the study of fungi
 Parasitology is the study of parasites
 Virology is the study of viruses
 Immunology is the study of immunity
 Toejamology is the study of fungal foot infections
Topic 2: Microscopy
List the metric units of measurement:
 SI unit if measure is the metre, 10^-3 m = 1 mm; 10^-6 m = 1 µm (micrometre) and 10^-9 m
= 1 nm (nanometre)
Define light microscopy terms:
 Visible white light consists of light radiation between 400-750 nm
 Reflection is light hitting a specimen and the observable reflected light
 Transmission is the transmitted light that comes off the other side after entering a specimen
 Absorption is light entering a specimen that is absorbed and doesn’t come out the other side
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Refraction is light that is bent at an angle so it is transmitted at a different relative to it
entering the specimen
Luminescence is the emission of light by a specimen
Phosphorescence is similar to fluorescence except that light emission by the specimen
continues after the illumination has stopped
Fluorescence is light, usually of shorter wavelengths absorbed by the specimen which excites
the molecules of the specimen to emit different (longer) wavelengths of light. Filters in the
pathway of the light can block the exciting light so we only see the fluorescent light.
Identify the parts of a microscope:
 Ocular lens remagnifies the image formed by the objective lens
 Body tube transmits the image from the objective lens to the ocular lens
 Objective lens is the primary lens the magnifies the specimen
 Stage holds the microscope slide
 Condenser focuses light through the specimen
 Diaphragm controls the amount of light entering the condenser
 Illuminator is the light source
Draw the light path through the microscope:
 Illuminator, condenser lens, specimen, objective lens, body tube, prism, and ocular lens
 Lenses change the light path and make the image appear upside down and back to front
Define total magnification, resolution and refraction:
 Total magnification is the objective lens magnification times the ocular lens magnification
 Resolution is the ability of lenses to focus between two points
 Shorter wavelengths provide greater resolution and greater than or equal to 200 nm is
maximum resolution for a light microscope
 Refraction is a distortion of the specimen image corrected by oil immersion to re-bend the
light and correct the image
Electron microscopy vs light microscopy:
 Transmission Electron Microscopy (TEM) has an electron beam wavelength of 0.005 nm and
can resolve 0.0025 nm and magnify ten to one hundred thousand times
 Scanning Electron Microscopy (SEM) involves drying the specimen and coating it with heavy
metal ions, scanning the surface of the specimen with a beam of electrons. The heavy metal
ions refract the electrons and produce an image.
Differentiate between an acidic and a basic dye:
 Staining is colouring a microbe with a dye to emphasize certain structures
 A smear is a thin film of a solution of microbes on a slide
 A smear is usually fixed to attach the microbes to the slide and kill them
 Acidic dyes are anionic with negative charges on the chromophore, whereas negative dyes
are cationic with a positive charge on the chromophore
 Positive staining: the surfaces of microbes are negatively charged and attract basic dyes and
negative staining: microbes repel the dye and it stains the background
Explain the purpose of simple staining:
 Simple staining involves a single dye like methylene blue, saffranin or crystal violet
 Differential staining involves two or more dyes to stain different structures or organisms and
include the Gram stain and the acid-fast stain
 Special staining are stain for particular structures like endospores, capsules or flagella
List the step in preparing a Gram stain:
 Gram positive are stained blue by crystal violet and Gram negative are stained red with
saffranin
 Gran non-reactive stain poorly with counter stain and Gram-variable can have blue and red
cells in the same population
Gram stain vs acid-fast stain:
 This stain uses carbolfuchsin red, the cells are washed with hot acid, then counter stained
with methylene blue
 The cells retaining the red stain of carbolfuchsin are acid-fast. This stain stains the lipid
components of the cell wall
 Eg, Mycobacterium, causes TB, will stain red because it is acid-fast
Capsule, endospore and flagella stains:
 Endospore: primary stain is malachite green and usually with heat. Water decolourizes the
cells and safranin is the counter stain
 Capsule stains are a negative stain and appear as a clear area around the cells
 Flagella stains use a carbolfuchsin simple stain and a mordant on the flagella