BIO 175 Exam #2 Questions and Answers
discuss characteristics of biofilms that differentiate them from planktonic bacteria -
biofilms are communities of bacteria and/or other microbes that are attached to a surface and to
each other, forming a multilayer conglomerate of cells and intracellular material
-bacteria can use quorum sensing to interact with other members of the same species, as well as
members of other species that are close by
-eventually large complex communities are formed, which have different physical and biological
characteristics in different locations of the community
-the bottom of a biofilm may have a very different pH and oxygen conditions than the surface of
a biofilm; it is clearly established that microbes in a biofilm, as opposed to those in a planktonic
(free floating) state, behave and respond very differently in their environments
-different genes are even activated in the two situation and at any rate, a single biofilm is actually
a partnership among multiple microbial inhabitants and thus cannot be eradicated by traditional
methods targeting individual infections
summarize the steps of cell division used by most bacteria -binary fission: the formation
of two new cells
,-the parent cell enlarges, duplicated its chromosome, and then starts to pull its cell envelope
together in the center of the cell using a band of protein that is made of substance that resemble
actin and tubular (the protein in microtubules in eukaryotic cells)
-the cell wall eventually forms a complete central septum and this process divides the cell into
two daughter cells and then is repeated
define doubling time and describe how it leads to exponential growth -doubling time:
also called generation, the time required for a complete fission cycle, from one parent cell to two
new daughter cells
-each new fissions cycle increases the population by a factor of 2, or doubles it and as long as
conditions are favorable it will continue
-the shortest generation can be 10 to 12 mins
compare and contrast the four phases of growth in a bacterial growth curve -growth
curve: a graphical representation of the change in population size overtime; has four phases
-lag phase: the early phase of population growth which no signs of growth occurs, but cell is
doubling contents
-exponential growth (log) phase: cells reach the maximum rate of cell division as long as cells
have adequate nutrients and the environment is favorable
,-stationary growth phase: survival mode in which cells either stop growing or grow very slow;
the decline in the growth rate is caused by depleted nutrients and oxygen plus excretion of
organic acids and other biochemical pollutants in the growth medium, due to the increased
density of cells
-death phase: end of the cell growth due to the lack of nutrition, depletion of environment, and
accumulation of wastes, population begins to die
identify one culture based and one non culture based method used for analyzing bacterial growth
-non culture based method is turbidity which relies on the simple observation that a tube
of clear nutrient solution becomes cloudy, or turbid, as microbes grow in it
-culture based method is counting which counts cells that are spread across a slide under a
microscope but an inaccuracy is that there is no distinction between dead and live cells so both
are included in the count
clearly define the terms sterilization, disinfection, decontamination, sanitization, antisepsis, and
degermation -sterilization: process that destroys or removes all viable microorganisms
(including viruses); the term sterile should be used only in the strictest sense to refer to materials
that been subjected to the process of sterilization (there is no such thing as slightly sterile); an
example is sterilants (chemical agents capable of destroying endospores)
-disinfection: physical process or a chemical agent to destroy vegetative pathogens but not
bacterial endospores, removes harmful products of microorganisms (toxins) from material;
, normally used on inanimate objects bc the concentration of disinfectants required to be effective
is harmful to human tissue; examples include bleach, iodine, and heat (boiling)
-decontamination/sanitization: cleansing technique that mechanically removes microorganisms
as well as other debris to reduce contamination to safe levels; important to restaurants, dairies,
breweries, and other commercial entities that handle large numbers of soiled utensils/containers;
examples include soaps, detergents, and commercial dishwashers
-antisepsis/degermation: reduces the number of microbes on the human skin, a form of
decontamination but on living tissues; involved scrubbing the skin (mechanical friction) or
immersing it in chemicals; examples include alcohol and surgical hand scrubs
identify the microorganisms that are most resistant and least resistant to control measures
-bacterial endospores have traditionally been considered the most resistant microbial
entities
-most gram-postive bacteria and enveloped viruses are considered less resistant
compare the action of microbicidal and microbistatic agents -microbicide: is compared to
germicide (an agent lethal to non endospore forming pathogens), are chemicals that kill
microorganisms
-the root -cide meaning "having the capacity to kill;" bactericide is a chemical that destroys
bacteria except those for those in the endospore stage, fungicide can kill fungal spores hyphae
and yeasts, sporicide is capable of destroying bacterial endospores
discuss characteristics of biofilms that differentiate them from planktonic bacteria -
biofilms are communities of bacteria and/or other microbes that are attached to a surface and to
each other, forming a multilayer conglomerate of cells and intracellular material
-bacteria can use quorum sensing to interact with other members of the same species, as well as
members of other species that are close by
-eventually large complex communities are formed, which have different physical and biological
characteristics in different locations of the community
-the bottom of a biofilm may have a very different pH and oxygen conditions than the surface of
a biofilm; it is clearly established that microbes in a biofilm, as opposed to those in a planktonic
(free floating) state, behave and respond very differently in their environments
-different genes are even activated in the two situation and at any rate, a single biofilm is actually
a partnership among multiple microbial inhabitants and thus cannot be eradicated by traditional
methods targeting individual infections
summarize the steps of cell division used by most bacteria -binary fission: the formation
of two new cells
,-the parent cell enlarges, duplicated its chromosome, and then starts to pull its cell envelope
together in the center of the cell using a band of protein that is made of substance that resemble
actin and tubular (the protein in microtubules in eukaryotic cells)
-the cell wall eventually forms a complete central septum and this process divides the cell into
two daughter cells and then is repeated
define doubling time and describe how it leads to exponential growth -doubling time:
also called generation, the time required for a complete fission cycle, from one parent cell to two
new daughter cells
-each new fissions cycle increases the population by a factor of 2, or doubles it and as long as
conditions are favorable it will continue
-the shortest generation can be 10 to 12 mins
compare and contrast the four phases of growth in a bacterial growth curve -growth
curve: a graphical representation of the change in population size overtime; has four phases
-lag phase: the early phase of population growth which no signs of growth occurs, but cell is
doubling contents
-exponential growth (log) phase: cells reach the maximum rate of cell division as long as cells
have adequate nutrients and the environment is favorable
,-stationary growth phase: survival mode in which cells either stop growing or grow very slow;
the decline in the growth rate is caused by depleted nutrients and oxygen plus excretion of
organic acids and other biochemical pollutants in the growth medium, due to the increased
density of cells
-death phase: end of the cell growth due to the lack of nutrition, depletion of environment, and
accumulation of wastes, population begins to die
identify one culture based and one non culture based method used for analyzing bacterial growth
-non culture based method is turbidity which relies on the simple observation that a tube
of clear nutrient solution becomes cloudy, or turbid, as microbes grow in it
-culture based method is counting which counts cells that are spread across a slide under a
microscope but an inaccuracy is that there is no distinction between dead and live cells so both
are included in the count
clearly define the terms sterilization, disinfection, decontamination, sanitization, antisepsis, and
degermation -sterilization: process that destroys or removes all viable microorganisms
(including viruses); the term sterile should be used only in the strictest sense to refer to materials
that been subjected to the process of sterilization (there is no such thing as slightly sterile); an
example is sterilants (chemical agents capable of destroying endospores)
-disinfection: physical process or a chemical agent to destroy vegetative pathogens but not
bacterial endospores, removes harmful products of microorganisms (toxins) from material;
, normally used on inanimate objects bc the concentration of disinfectants required to be effective
is harmful to human tissue; examples include bleach, iodine, and heat (boiling)
-decontamination/sanitization: cleansing technique that mechanically removes microorganisms
as well as other debris to reduce contamination to safe levels; important to restaurants, dairies,
breweries, and other commercial entities that handle large numbers of soiled utensils/containers;
examples include soaps, detergents, and commercial dishwashers
-antisepsis/degermation: reduces the number of microbes on the human skin, a form of
decontamination but on living tissues; involved scrubbing the skin (mechanical friction) or
immersing it in chemicals; examples include alcohol and surgical hand scrubs
identify the microorganisms that are most resistant and least resistant to control measures
-bacterial endospores have traditionally been considered the most resistant microbial
entities
-most gram-postive bacteria and enveloped viruses are considered less resistant
compare the action of microbicidal and microbistatic agents -microbicide: is compared to
germicide (an agent lethal to non endospore forming pathogens), are chemicals that kill
microorganisms
-the root -cide meaning "having the capacity to kill;" bactericide is a chemical that destroys
bacteria except those for those in the endospore stage, fungicide can kill fungal spores hyphae
and yeasts, sporicide is capable of destroying bacterial endospores
