CHAPTER 3
Basic Techniques in the Manipulation of Microorganisms
The 5 I's summarize the kinds of laboratory procedures used in microbiology.
Inoculation
Incubation
Isolation
Inspection
Identification
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Inoculation
Introduction of inoculum into a growth medium.
The observable growth is called a 'culture'.
Pure culture = axenic culture.
Inoculating tools include:
Loops
Neeedles
Pipettes
Swabs
Obligate parasites (including viruses and some bacteria) can not grow on artificial media.
These organisms require live cell cultures or host animals.
Sterile conditions: a basic requirement for microbiological work.
Contamination is caused by unwanted microorganisms of uncertain identity.
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Colony
A macroscopically visible population of cells growing on solid medium, arising from a single cell
A macroscopically cluster of cells appearing on a solid medium, each arising from the multiplication of a single cell
A visible assemblage of microorganisms growing on a solid surface (agar).
Generally originated from the reproduction a single cell.
A microbial colony has distinctive size, shape, color and texture.
Colonies
originate pure cultures.
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Strain
A
group of descendants of an original cell.
Bacterial strains of E. coli belong to the same species.
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Microbial Culture
A particular strain or kind of organism growing in a laboratory medium.
The
visible accumulation of microorganisms in or on a nutrient medium.
A strain growing in a laboratory medium.
The largest collection of fungal, bacterial, algal and viral cultures is the American Type Culture Collection located in Rockville, Maryland, USA.
There
are culture collections in research centers, institutions, universities and
others sites around the world.
Microbial germplasm collections preserve genetic pool.
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Subculturing
It is the removal of a small sample from a culture and its transference to a separate container or media.
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Growth media
Medium (singular), media (plural)
Microbiologists have many types of media at their disposal, with new ones, being develop all the time.
Some microbes require only a very few simple inorganic compounds for growth; others need a complex list of specific inorganic and organic compounds.
At least 500 different types of media are used in culturing and identifying microorganisms.
Culture
media are contained in Petri dishes, test tubes, flasks and inoculated with
loops, needles, pipettes, and swabs.
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Types of media
Media can be classified according to three properties:
Physical state
Includes liquid, semisolid, liquefiable solid, or nonliquafiable solid.
Chemical composition
Includes synthetic or nonsynthetic, depending on the precise content of their chemical composition.
Functional type
As either general-purpose media or media whith one or more specific purposes.
Includes enriched, selective, differential, transport, assay, and enumerating media.
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Remember to read
your textbook, study tables, graphs and illustrations.
Develop a strategy to administer your time so that when exams come you do not
have to cram.
Attend lectures and ask questions.
Lecture notes are posted BEFORE lecture is given thereafter they will be removed.