History & Scope of Microbiology(BHSc)

8/13/2019 History & Scope of Microbiology(BHSc)

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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

History & Scope of Microbiology(BHSc)

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