LSU BIOL 2051 Lab midterm
Questions and Answers.
Culture medium - Answer microorganisms can be grown in them; composed of digests of
chemically undefined substances such as yeast and meat extracts
Defined medium - Answer precise chemical composition is known
Broth - Answer liquid culture medium
Solid medium - Answer culture medium containing a solidifying agent, usually agar
Plates - Answer solid media in Petri dishes
Deeps - Answer test tubes containing solid medium, usually used for anaerobic growth
Slants - Answer test tubes containing solid medium that has been allowed to solidify at an
angle and the surface of the agar is used for the maintenance of stock cultures of
microorganisms
Sterilization - Answer killing or removal of all living organisms and their viruses from a
growth medium
Autoclave - Answer sealed device that allows the entrance of steam under pressure, heated
to 121°C at 15 psi for 15 minutes; sterilizes liquid media and other items that are heat-resistant
Dry heat sterilization - Answer kills by oxidation effects; simplest kind is flaming
Hot air sterilization - Answer items to be sterilized are placed in an oven and heated to 170°C
for 2 hours; useful for glassware
Filtration - Answer sterilization of heat-sensitive liquids or gases
Gaseous chemosterilizers - Answer sterilization of other heat sensitive objects such as plastic
Petri dishes; one widely used gas is ethylene oxide
Cold sterilization - Answer method of sterilization without heat; ex. Gaseous chemosterilizers
, Electromagnetic radiation - Answer sterilization using microwaves, UV, x-rays, gamma rays,
and electrons
Ultraviolet (UV) radiation - Answer causes damage to the DNA (thymine dimers) leading to
the death of exposed organisms; useful in sterilizing only exposed surfaces
Ionizing radiation - Answer causes ions and other reactive molecules to be produced and
these reactive molecules can degrade or alter biopolymers such as DNA and proteins
Pathogenic - Answer disease-causing for humans; minority of microorganisms
Nosocomial - Answer hospital-acquired infections; prevented by proper sterilization
techniques (cleaning and washing hands are essential)
Infectious dose - Answer number of microorganisms of viruses sufficient to establish and
infection
Normal or resident microbiota (flora) - Answer establish themselves on or in the body, but
do not produce disease under normal conditions
Transient microbiota (flora) - Answer may be present on the body temporarily but do not
become firmly entrenched; come into contact with skin constantly, but most organisms are
unable to multiply there and will die
Acidic - Answer pH of the skin is acidic, ranging from 4 to 6
Colonies - Answer formed by microorganisms growing on a solid culture medium
Colony - Answer given rise to by a single cell replicating
Colony morphology - Answer shape of the colony, form of the colony margin, and elevation
and pigmentation of the colony; visible to the naked eye; see figure on page 14
Contaminant - Answer an unwanted organism which has been accidentally introduced into
the culture
Questions and Answers.
Culture medium - Answer microorganisms can be grown in them; composed of digests of
chemically undefined substances such as yeast and meat extracts
Defined medium - Answer precise chemical composition is known
Broth - Answer liquid culture medium
Solid medium - Answer culture medium containing a solidifying agent, usually agar
Plates - Answer solid media in Petri dishes
Deeps - Answer test tubes containing solid medium, usually used for anaerobic growth
Slants - Answer test tubes containing solid medium that has been allowed to solidify at an
angle and the surface of the agar is used for the maintenance of stock cultures of
microorganisms
Sterilization - Answer killing or removal of all living organisms and their viruses from a
growth medium
Autoclave - Answer sealed device that allows the entrance of steam under pressure, heated
to 121°C at 15 psi for 15 minutes; sterilizes liquid media and other items that are heat-resistant
Dry heat sterilization - Answer kills by oxidation effects; simplest kind is flaming
Hot air sterilization - Answer items to be sterilized are placed in an oven and heated to 170°C
for 2 hours; useful for glassware
Filtration - Answer sterilization of heat-sensitive liquids or gases
Gaseous chemosterilizers - Answer sterilization of other heat sensitive objects such as plastic
Petri dishes; one widely used gas is ethylene oxide
Cold sterilization - Answer method of sterilization without heat; ex. Gaseous chemosterilizers
, Electromagnetic radiation - Answer sterilization using microwaves, UV, x-rays, gamma rays,
and electrons
Ultraviolet (UV) radiation - Answer causes damage to the DNA (thymine dimers) leading to
the death of exposed organisms; useful in sterilizing only exposed surfaces
Ionizing radiation - Answer causes ions and other reactive molecules to be produced and
these reactive molecules can degrade or alter biopolymers such as DNA and proteins
Pathogenic - Answer disease-causing for humans; minority of microorganisms
Nosocomial - Answer hospital-acquired infections; prevented by proper sterilization
techniques (cleaning and washing hands are essential)
Infectious dose - Answer number of microorganisms of viruses sufficient to establish and
infection
Normal or resident microbiota (flora) - Answer establish themselves on or in the body, but
do not produce disease under normal conditions
Transient microbiota (flora) - Answer may be present on the body temporarily but do not
become firmly entrenched; come into contact with skin constantly, but most organisms are
unable to multiply there and will die
Acidic - Answer pH of the skin is acidic, ranging from 4 to 6
Colonies - Answer formed by microorganisms growing on a solid culture medium
Colony - Answer given rise to by a single cell replicating
Colony morphology - Answer shape of the colony, form of the colony margin, and elevation
and pigmentation of the colony; visible to the naked eye; see figure on page 14
Contaminant - Answer an unwanted organism which has been accidentally introduced into
the culture
