What is Microbiology?

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What is Microbiology?
Microbiology is the Science that studies
Microorganisms.
Microorganisms, roughly, are those living things
that are too small to be seen with the naked eye.
Microorganisms cannot be distinguished
Phylogenetically from Macroorganisms, e.g.,
includes fungi as well as bacteria, etc.
Microbiology is more a collection of techniques

• Aseptic technique

• Pure culture technique

• Microscopic observation of whole organisms

• etc.

A microbiologist usually first isolates a
specific microorganism from a population and then
cultures it.
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Relative Microbe Sizes
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Microbes Ecology

• Microbes are producesthey provide energy to
  ecosystems
• Microbes are fixersthey make nutrients available
  from inorganic sources, e.g., nitrogen
• Microbes are decomposersthey free up nutrients
  from no longer living sources
• Microbes form symbioses (such as mycorrhizal
  fungi associated with plant rootsthough these
  are somewhat macroscopic also the bacteria found
  in legume root nodules, etc.)
• Microbes serve as emdosymbionts (e.g.,
  chloroplasts and mitochondria)

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Microbes Industry

• Industry Fermentation products (ethanol,
  acetone, etc.)
• Food Wine, cheese, yogurt, bread, half-sour
  pickles, etc.
• Biotech Recombinant products (e.g., human
  insulin, vaccines)
• Environment Bioremediation

Each carton of BugsPlus provides easy to follow
step-by-step instructions, containers of
specially-formulated wet and dry nutrients and a
container of microbes cultured for their ability
to digest oil and other petroleum derivatives.
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Microbes Disease

• Microbes both cause and prevent diseases (for
  latter antibiotics are made by microbes and
  normal flora interfere with pathogen replication)
• Microbes produce antibiotics used to treat
  diseases
• The single most important achievement of modern
  medicine is the ability to treat or prevent
  microbial disease
• The Germ Theory of Disease Microbes cause
  disease!
• Yes, it wasnt so long ago that humans didnt
  know that unseen, microscopic organisms can cause
  animal and plant diseases

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Brueghel The Triumph of Death (1560)
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Normal Flora
These are the harmless microorganisms found on
your body.
Every part of your body that normally comes in
contact with outside world (deep lungs and
stomach are exceptions)
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Viruses
Viruses are ...infectious agents of small size
and simple composition that can multiply only in
living cells of animals, plants and bacteria
plus fungi protozoa. Viruses are obligate
parasites that are metabolically inert when they
are outside their hosts. They all rely, to
varying extents, on the metabolic processes of
their hosts to reproduce themselves. The viral
diseases we see are due to the effects of this
interaction between the virus and its host cell
(and/or the hosts response to this
interaction). Encyclopedia Britannica
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Virus (Virion Particle)

• The Virion is what defines a virus as a virus
• A Virion is the extracellular state of a virus
• The job of Virions is to find new cells to infect
• As such, Virions are a durable state that is
  designed to attach to susceptible cells
• The Virion is then responsible for translocation
  of the virus genome into the cell
• The Virion consists of a DNA (or RNA) genome
  surrounded by Protein that, in turn, may be
  surrounded by a Lipid Bilayer
• The Protein layer is called a Capsid
• The Lipid Bilayer is called an Envelope

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Virus (Virion Particle)
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Capsid (Nucleocapsid)

• The Capsid is the protein shell surrounding the
  virus nucleic-acid genome
• A Nucleocapsid is that combination of protein
  capsid and nucleic-acid genome
• Capsids consist of multiple subunits of one or
  more types of protein
• Capsomere(s) capsid protein subunits
• For viruses with complex morphologies the capsid
  may consist of many (10s of) different types of
  capsomer proteins, with additional proteins
  involved simply in capsid morphogenesis
• Capsids are responsible for nucleic-acid
  protection and penetration into cells

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Virus Envelopes (Spikes)

• In addition to the capsid, many animal viruses
  additionally posses Envelopes
• An Envelope is a lipid bilayer that surrounds the
  nucleocapsid
• For enveloped viruses the envelope is also (in
  addition to the capsid) involved in nucleic-acid
  protection and penetration
• Without an envelope an otherwise enveloped virus
  is not mature nor infectious
• Enveloped proteins often have Glycoproteins
  (Spikes) projecting from their envelopes that are
  involved in virus infection
• For Non-Enveloped viruses the capsid is solely
  responsible for nucleic-acid protection and
  penetration

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Virus Classification

• Viruses are classified
• According to their Genome Type
• Their Virion Morphology (as determined by
  electron microscopy)
• Their strategies of replication
• Their Serology (serotype), which is their
  reaction with specific antiserum
• (Increasingly) in terms of the sequence of their
  genomes
• International Committee on Taxonomy of Viruses
  (ICTV)

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Viral Genomes
http//www.virology.net/Big_Virology/BVFamilyGenom
e.html
One way to distinguish different types of viruses
(e.g., influenza virus from HIV) is in terms of
the characteristics of their nucleic-acid genomes
Nucleic-Acid Virus Genome
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Steps of Virus Replication

• Adsorption (attachment)
• Penetration (nucleic-acid release)
• Synthesis (of RNA and proteins, as well as DNA if
  DNA genome)
• Maturation (assembly of virion)
• Release (lysis or chronic release, e.g., budding,
  with the latter coinciding with release for
  various enveloped viruses)

Caveat It is important to realize that variation
among viruses is between virus strains/species
any one kind of virus cannot replicate in
multiple ways, have more than one virion
morphology, or vary in genome type, etc.
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Lytic Phage Infection Cycle
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Temperate Phage Infection Cycle
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Naked Animal Virus Infection
Lysis!
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Enveloped Virus Infection
Budding, Not Lysis!
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HIV Infection Cycle
Budding, Not Lysis!
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Bacteria Sex

• Viruses move genetic material from cell to cell
• Mostly this material is their own genomes, i.e.,
  genes that collectively code for the production
  of new viruses
• Bacteria DNA also can move from cell to cell
• Once received by a cell, this DNA may be
  incorporated into the bacterial genome via
  recombination
• This idea of DNA sourced from different parents
  recombining into a single chromosome is
  equivalent to eukaryotic sex (i.e., fertilization
  followed by recombination)
• Transformation, Transduction, Conjugation

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Transformation
Transformation DNA picked up directly from the
medium and recombined into the genome
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Transduction
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Plasmids
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Conjugation
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Resistance Plasmids
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Bacterial Genotype ? Phenotype

• Bacterial response to environmental change
• Control of gene expression
• Lac operon (response to presence of lactose)
• Trp operon (response to presence of tryptophan)
• Catabolite Repressor Protein (response to
  presence of glucose)

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Lac Operon without Lactose
Enzymes required for Lactose Digestion are
synthesized (to any great extent) only when
Lactose is present in the environment
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Lac Operon with Lactose
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Negative Control
Protein-DNA binding Inhibits Transcription
Also Inducible Operon since lactose binding ?
transcription
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Trp Operon without Trp
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Trp Operon with Trp
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Feedback Inhibition
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Negative Control
Protein-DNA binding Inhibits Transcription
Also Corepressed Operon since Trp binding ?
transcription
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Catabolite Repressor Protein
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Positive Control
Protein-DNA binding Enhances Transcription
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Link to Next Presentation
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Acknowledgements
http//207.233.44.253/wms/reynolmj/lifesciences/le
cturenote/bio3/Chap10.ppt http//www.bbchs.k12.il
.us/Teacher_Pages/Hammond/Powerpoint/Chapter_18.pp
t
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Prion Action
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Transposition