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Define and discuss the scope of Microbiology
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?Microbiology Study of microscopic organisms (organisms that
are invisible to the naked eye)
All organisms other than viruses and prions are
made up of cells.
Prions: infectious particle that lacks nucleic acids
and replicates by converting similar normal
proteins into new prions.
All other organisms have a cellular organization
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On completion of this module you should
be able to define and discuss the scope of Microbiology
learn why you study Microbiology
learn History and Development of Microbiology
discuss the slow rate of spontaneous generation
discuss the role of a Medical Microbiologist
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It is the study of theirShape
StructureReproduction
PhysiologyMetabolism
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It is the study of their Classification
Distribution in nature
Relationwith each other & other living organisms
Ability to change physicallyand chemically
Their reaction to physical & chemical agents
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Classification of Microorganisms Bacteria: simple, single cell (prokaryotic cells
with cell walls and peptidoglycan).
Fungi:single & multi cellular forms - yeast,
filamentous molds, and complex fungi.
Viruses: acellular, intracellular parasites Protists: single cell, some multicellular - algae,
protozoans, slime molds
Worms: multicellular, more complex
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SCOPE OF MICROBIOLOGY Impacton Human Health
Balance of Nature : food source, play a role in
decomposition, help other animals digest grass
(cattle, sheep, termites).
Environmental: provide safe drinking water;
development of biodegradable products; use
bacteria to clean up oil spills, etc.called
bioremediation.
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Bacteriology: study of bacteria
Prokaryotes
Bacteriaare prokaryotes, all other organisms are
eukaryotes.
How may bacteria obtain energy?
heterotrophs : depend on outside sources of
organic molecules (ex. carbohydrates or sugars)
for energy
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Prokaryotes
A distinct nucleus is absent
DNA is in the form of a single circular
chromosome Additional DNA is carried in
plasmids
Transcriptionand translationcan be carried out
simultaneously.
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How may bacteria obtain energy?
heterotrophs: depend on outside sources of
organic molecules (ex. carbohydrates or sugars)
for energy
chemosynthetic autotrophs: process inorganic
molecules for energy (ex. sulfur or iron).
photosynthetic autotrophs: use energy from the
sun to produce their own carbohydrates for
energy.
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SUMMARY
Bacteria are prokaryotes. Their DNA is not
contained within a nucleus and there are
relatively few cytoplasmic organelles.
The cell wall is a key structure in metabolism,
virulence and immunity.
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Gram positive and Gram negative
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SUMMARY
The cell wall staining characteristics define the
two major divisions:
the Gram-positiveand Gram-negativebacteria.
Flagella may be present and confer motility.
Bacteria metabolize aerobically and
anaerobically and can utilize a range of
substrates.
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SUMMARY
The bacterial cell wall and their reproductive
processes are targetsfor antimicrobial agents
Transcription of bacterial DNA may involve single
or multiple genes. The arrangement of promoter
and terminal sequences flanking multiple genes
forms an operon
Bacteria can regulate gene expression to optimize
exploitation of their environment.
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Bacterial structure
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SUMMARY
Plasmids and bacteriophages are independently
replicating extrachromosomal agents. Plasmids
may also carry genes that affect resistance to
antimicrobials or virulence.
Genetic material can be carried from one
bacterium to another in several ways; this can
result in the rapid spread of resistance to
antimicrobials.
Genomics is revolutionizing the study and the
control of bacterial infections.
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Specialised Techniques Required to
isolate
Culture: On specialised media
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Mycology:study of fungi
(singular: fungus) Fungi: eukaryotic cells lacking cell walls and
contain nucleus of genetic material surrounded
by a membrane
Fungi are eukaryotes, but are quite distinct from
plants and animals. Characteristically, they aremultinucleate or multicellular organisms with a
thick chitin-containing cell wall
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Eukaryotes
DNAis carried on several chromosomes within a
nucleus
The nucleus is bounded by a nuclear membrane
Transcription requires formation of messenger
RNA (mRNA) and movement of mRNA out of the
nucleus into the cytoplasm
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Mycology:study of fungi (singular: fungus)
They may grow as thread-like filaments (hyphae),
but many other growth forms occur
Fungi are ubiquitous as free-living organisms and
are of enormous importance commercially in
baking, brewing and in pharmaceuticals
Normal flora,
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Characteristicsof fungi Eukaryotic
unicellular or multicellular (yeasts are unicellular,
molds are multicellular)
nonmotile
How do they obtain their energy?
heterotrophs
Why are they ecologically important?
Scavengers: they live off dead matter and thus,
decompose it.
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MAJOR GROUPS OF DISEASE-CAUSING FUNGI :called
mycoses
superf icial mycoseswhere the fungus grows at the body
surface on skin or hair
cutaneous and subcutaneous mycoseswhere nails and
deeper layers of the skin are involved
systemic or deep mycoseswith involvement of internal
organs. This category includes the opportunisticfungi
that cause disease in patients with compromised
immune systems
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Two ways of Classifying fungi
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SUMMARY
Fungi are distinct from plants and animals, have a
thick chitinous cell wall, and grow as filaments
(hyphae) or single-celled yeasts
Species causing disease may be acquired from the
environment or occur as part of the normal flora.
Infections may be located superficially, in
cutaneous and subcutaneous sites, or in deeptissues
Infections are most serious in immunocompromised
individuals
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All organisms other than viruses and
prions are made up of cells
Viruseshave genetic material (DNAor RNA) but lack
cell membranes, cytoplasm and the machinery for
synthesizing macromolecules, depending instead
upon host cells for this process
Conventional viruses have their genetic material
packed in capsules
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All organisms other than viruses and
prions are made up of cells
Prions cause diseases such as:
Creutzfeldt-Jakob disease
kuru, scrapie and bovine spongiform
encephalopathy (BSE) appear to lack nucleic acid
and consist only of proteinaceous infectious
particles.
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All organisms other than viruses and prions
are made up of cells All other organisms have a cellular organization
Their bodies being made up of single cells (most
'microbes') or of many cells
Each cell has genetic material (DNA) and
cytoplasm with synthetic machinery, and is
bounded by a cell membrane
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Normally Microorganisms are
unicellular
Bacteria are prokaryotes, all other organisms are
eukaryotes
There are many differences between the two major
divisions-prokaryotes and eukaryotes-of cellular
organisms
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Summary of Bacteria
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Two ways to classify fungi
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Protozoa
Protozoa are single-celled animals, ranging in sizefrom 2 m to 100 m
Many species are free-living, but others areimportant parasites of humans
Some free-living species can infect humansopportunistically, and some parasites cause severe
disease only in immunocompromised individuals
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Protozoa Infections are most prevalent in tropical and
subtropical regions, but also occur in temperateregions
Protozoa may cause disease directly (e.g. the
rupture of red cells in malaria), but more often thepathology is caused by the host's response
Most infections are not life threatening (except inimmunocompromised patients), but malaria killsmore than 1.5 million people each year, mostlyyoung children
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Protozoa can infect all the major
tissues and organs of the body
Protozoa infect body tissues and organs such as:
Intracellular parasites in a wide variety of cells (redcells, macrophages, epithelial cells, brain, muscle)
Extracellular parasites in the blood, intestine or
urinogenital system.
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Downloaded from: StudentConsult (on 11 January 2010 11:23 AM)
2005 Elsevier
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Viruses
Viruses differ from all other organisms in their
structure and biology, particularly in their
reproduction
Although viruses carry conventional genetic
information in their DNA or RNA, they lack the
synthetic machinery necessary for this information
to be processed into new virus material
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Viruses
A virus by itself is metabolically inert-it can
replicate only after infection of a host cell, when
it can parasitize the host's ability to transcribe
and/or translate genetic information
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Viruses
Viruses infect every form of life
They cause some of the commonest and many of
the most serious diseases of humans
Viruses
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Some insert their genetic material into the human
genome and can cause cancer
Viruses are difficult targets for chemotherapy, but
many can be controlled by effective vaccines
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Viruses share some common structural
features
Viruses range from very small (poliovirus, at 30
nm) to quite large (vaccinia virus, at 400 nm, is
as big as small bacteria). Their organization
varies considerably between the different
groups, but there are some general
characteristics common to all:
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Viruses share some common structural
features The genetic material, in the form of single-
stranded (ss) or double-stranded (ds), linearor circular RNA or DNA, is contained within a
capsule or capsid, made up of a number ofindividual protein molecules (capsomeres).
The complete unit of nucleic acid and capsidis called the 'nucleocapsid', and often has adistinctive symmetry depending upon the
ways in which the individual capsomeres areassembled
Symmetry can be icosahedral, helicalorcomplex.
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Virusesshare some common structural
features In many cases the entire 'virus particle' or 'virion'
consists only of a nucleocapsid
In others the virion consists of the nucleocapsidsurrounded by an outer envelope or membrane
This is generally a lipid bilayer of host cell origin,
into which virus proteins and glycoproteins are
inserted
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Symmetry and Construction of viral
nuleocapsid
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Construction of an enveloped virus
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Virus particles enter the body of the
host in many ways Via inhaled droplets (e.g. rhinovirus)
In food or water (e.g. hepatitis A) By direct transfer from other infected hosts
(e.g. HIV)
From bites of vector arthropods (e.g. yellow
fever)
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Routes by which viruses enter the body
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History
Spontaneous Generation Theory
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