Flashcards in Exam II Deck (291)
What three conditions can affect microbial growth?
different pH levels
different osmotic pressures
What are the cardinal temperatures?
What are the classification of organisms based on their cardinal temperatures?
Psychrophiles can only grow at temperatures less than _______.
20 C (-5 to 20)
Psychrotrophs typically have a growth range of ____ to ______
0 to 30 C
What percentage of bacteria can grow <= 10 C
Psychrophiles can be found in ____ ____, _______, and ________.
alpine soils, icefields, oceans
Psychrophiles are not human __________
Psychrotrophs can be found in ___, _____ ____, and in ______
soils, surface water, foods
Psychrotrophs can be human ______
Mesophiles have a typical range for growth of ___ to ____
15 to 40 C
Mesophiles have an optimal temperature that is approximately normal _____ _____ temperature.
Mesophilic bacteria can be human _______
Thermophiles have a typical range of growth of ____ to _____
40 to 75 C
Hyperthermophiles have a typical range for growth of ____ to _____
65 to 110 C
Thermophiles can be found growing in ____ ____
_______ can be isolated from ocean floor thermal vents/ridges.
pH is the concentration of _______ ions in a solution
pH is measured on a _______ scale from 0-14 based on the hydrogen concentration
Pure water is considered ______ and was assigned a pH of _____. This means that water has 10^-7 moles of H+ ions per liter.
As the concentration of H+ increases, the pH _____ and the solution becomes more _____
As the concentration of H+ decreases, the pH _____ and the solution becomes more ______
What are the three classifications of organisms based on the growth pH range?
Acidphiles grow well in acidic environments with a pH of <=
4.5 to 5.5
Alkaliphiles grow well in basic enviroments at a pH of >=
8 to 8.5
Acidophiles can be found growing in such places as ____ ____ _____ and the _____
acid mine drainage; stomach
Alkaliphiles can be found in the soil of ____ ____ or in places like the shores of Mono Lake, California where the pH is 10
Neutrophiles grow well at a neutral pH between ___ and ___
Most human ______ are neutraphiles since most bodily fluids are at neutral pH.
_____ is required by all forms of life including bacteria?
For bacteria ______ is necessary to maintian ____ pressure
______ pressure is the pressure inside a cell that is required for survival
If the correct turgor pressure is not maintained a bacterium could _____ (rupture) or ______ (shrink).
To regulate turgor pressure, bacteria maintain high concentration of ____ and ______ ions in their cytoplasm
High concentrations of potassium and sodium ions within the cell and lower concentrations of these ions outside the cell creates a _______ ______.
formation of a concentration gradient leads to ______
what is the movement of water from an area of low solute concentration to an area of high solute concentration in order to achieve equilibrium?
What is the force with which water flows from an area of low solute concentration to an area of high solute concentration?
What are the three types of osmotic environments a bacteria could encounter
In hypotonic enviroments, there is a _____ solute concentration inside the cell than outside which creates a ____ osmotic pressure, and water moves _____ the cell which causes the cell to ____.
higher; low; into; lysis
In isotonic environments, there is ______ solute concentration inside and outside the cell and water moves in and out of the cell at an ______ rate.
In hypertonic environments, there is a ____ solute concentration inside the cell than outside which creates a ____ osmotic pressure, and water moves ____ of the cell which causes the cell to ______.
lower; high; out; plasmolysis
The concentration of _____ in a solution can affect osmotic pressure.
Most bacteria survive and grow in salt concentrations
Bacteria that grow optimally at salt concentrations > 3% are called what?
Extreme halophiles can ONLY survive at salt concentrations between ____ and ____.
What type of bacteria can survive and grow over a wide range of salt concentrations?
Halophiles are used in the fermentation of foods products such as _____ ____.
What is the ability or inability to live in the presence of O2?
What must have O2 to survive and grow?
What can grow in the presence or absence of O2?
What do not need O2 but can survive in the presence of O2?
what survive only when O2 levels are low?
what can only survive when CO2 levels are high?
What can O2 kill?
What removes most free O2 from media; however; as the media cools oxygen starts to diffuse back into the media?
when media is in a tube the diffusion of O2 back into the broth or agar results in a ______ ______
the surface of the media in a tube will have a high O2 concentration while the media at the bottom with have ____ O2.
Bacteria will grow where the O2 _______ in the tube is optimal for that organism
____ media is used in an agar deep stab to ensure that the bottom of the tube is anaerobic.
bacteria are stabbed once all the way to the ______ of the tube with an inoculating needle
What are the important ingredients in fluid thioglycollate medium?
What is the purpose of sodium thioglycollate?
reducing agent (reduces O2 to water)
What is the purpose of L-cystine?
reducing agent (reduces O2 to water
What is the purpose of Resazurin
turns red/pink in the presence of O2
straw color in the absence of O2
Tubes of aerotolerant organisms will appear what?
cloudy all over
facultative anaerobes will be appear how in a tube?
concentrated at top but growth throughout
Obligate anaerobes will grow where in a tube?
only at bottom
Obligate aerobes will grow where in a tube?
only at top
what are used to produce anaerobic conditions required for aerotolerance examination of plates?
The GasPak become activated by exposure to air and ______ is produced
How long does it take for anaerobic conditions to be reached with a GasPack?
around 2.5 hours
Methylene blue strip or tablet turns what color in the presence of O2?
Wht is the most common reason anaerobic conditions were not achieved?
not proper sealing; hole in plastic bag
The majority of bacteria are what in terms of oxygen tolerance?
are most anaerobic bacteria pathogens?
Anaerobic chambers are often used to study _____
Bacteria replicate by what?
What is the time taken to get from 2^x to 2^(x+1)
The average doubling time is generally between what?
20 to 60 minutes
environmental factors like temperature, pH, and nutrient availability can have a direct impact on the _____ ____ of an organism.
in a laboratory setting the effects of various environmental factors on a bacterium's growth rate can be examined using a _____ _____ ______.
Closed Growth System
A closed-growth system is an environment in which ____ nutrients are added and ____ waste products are removed
How many distinct phases of growth can be observed in a closed growth system and what are they?
4, Lag, Logarithmic, Stationary, Death
Which phase is the initial phase of the growth curve where the organisms are acclimating to a new environment?
During which phase is there no cell division but is a time of high metabolic activity in preparation for growth?
The more drastic the change in the environment, the longer the ____ phase is.
After a bacterium is acclimated to a new environment, it begins to divide during which stage?
During what phase is the maximum growth rate exponential and at regular intervals of time?
When the number of bacteria versus time is plotted on a ___ ____ the ascending straight line on the curve represents the exponential growth phase.
You can determine the generation time using which phase?
Which stage do nutrients become limited and the waste products begin to accumulate leading to an unfavorable environment?
Which phase does the growth rate equal the death rate?
The length of the stationary phase can vary among _____ bacterial species
During which phase are all the nutrients depleted and the levels of waste products toxic?
During which phase do bacteria begin to die faster than they grow?
Depending on what will the death occur at rapid rate or be gradual?
the bacterial species
If bacteria die but do not _____ there may not be a loss of turbidity and a obvious death phase will not be observed unless viable plate counts are done
A bacterial growth curve can provide the length of time the bacterium is in each ____ ____.
A bacterial growth curve can provide the ______ growth conditions of a bacterium
A bacterial growth curve can provide the mean _____ ____ of the organism
Bacteria replicate using what?
Nf equals what?
Environmental factors like what have a direct impact on the doubling time of an organism?
Temperature, pH, and nutrient availability
The average doubling time for bacteria is what?
20 to 60 min
What is used to observe the effects of various environmental factors on a bacterium’s growth rate?
Closed growth system
In a closed growth system, ______ nutrients are added and ______ waste products are removed.
What are the direct methods to measure the growth of bacteria
Filtration and plate counts
Most probably number (MPN)
What are the pros and cons of plate counts?
Pros - measures # of viable cells
Cons- time consuming and assumes that each bacterium grows and divides to produce a single colony
What are the pros and cons of filtration and plate counts?
Pros - measures # of viable cells in a small quantity
Cons - time consuming and assumes that each bacterium grows and divides to produce a single colony
What are the pros and cons of most probable numbers?
Pros - can be used for bacteria that cannot grow on solid media
Cons - only a statement that there is a 95% statistical chance that a bacterial population falls within a certain range
What are the pros and cons of direct counting using manual counting?
Pros - very accurate and relatively inexpensive
Cons - very tedious and time consuming
What are the pros and cons of direct counting using electronic cell counters?
Pros - very accurate and results obtained relatively quickly
Cons-expensive equipment that requires significant training in order to operate
What are some indirect ways to measure the growth of bacteria?
What indirect method assumes that the amount of the metabolic product is directly proportional to the # of bacteria present?
What is one of the quickest, easiest, and most common method for assessing bacterial growth?
What device is used to measure turbidity?
What kind of beam of light is used to measure the percent transmittance or absorbance
What is transmittance?
The fraction of incident light that passes through a sample
T= intensity of light out/intensity of light in
Produces an exponential curve
What is absorbance and what is it equal to?
The quantity of light that a sample neither transmits nor reflects; Optical density
What kind of relationship exists between absorbance and concentration?
Absorbance ranges from what to what?
0 to 1.99 A
If a sample is 1.99 A or above what should you do to it?
If a sample is diluted 1:5 and the absorbance of this diluted samples is 0.8 A. What was the absorbance of the original sample?
0.8 * 5 = 4
Each McFarland standard represents a specific what?
Bacterial cell concentration
How do you plot a standard curve using McFarland Standards?
Plot Absorbance vs Concentration
The Oxidation-Fermentation Test determines what?
What catabolic pathway a bacterium can use to break down a carbohydrate
What are examples of catabolic pathways?
In Aerobic respiration what is the final electron acceptor and what is required in the environment.
In fermentation what is the final electron acceptor and what can it occur in the presence or absence of?
Organic molecule; O2
Aerobic respiration occurs only in the presence of what?
During aerobic respiration a small amount of what are produced?
Acidic intermediate compounds
In fermentation large amounts of what are produced?
What are the two important media components of oxidation fermentation medium?
PH indicator like Bromthymol blue
The initial pH of the OF medium is ______ and the color of the medium is _______.
If the pH drops to _______ the media turns what color?
In order to produce an anaerobic environment to promote fermentation, the top of the OF medium can be overlayed with what?
Sterile mineral oil
If an organism can only use the oxidation pathway then the color of the OF tube overlayed with sterile mineral oil will be what?
If an organism can only use the oxidation pathway, then in the presence of oxygen the OF tube will show that a moderate amount of acidic compounds were produced so the media will be what color only at the top?
If an organism is capable of fermentation or fermentation and oxidation then the OF tube either overlayed with mineral oil or exposed to oxygen will be what color?
If an organism is a weak fermenter then the OF tube that is both covered with mineral oil or exposed to oxygen will be what color?
Yellow at the top of both
If the organism cannot metabolize the carbohydrate in the OF tube then both the mineral oil covered tube and the tube exposed to oxygen will be what color?
What test is used to determine what carbohydrate a bacterium can ferment?
Phenol Red broth test
The end products generated by fermentation are what?
Alcohols, acids, and gas
What are the three important points to remember about the fermentation pathway?
1. Glucose is not the only carbohydrate that can be used in glycolysis
2. The end products of fermentation include acidic compounds
3. Gas can also be an end product of fermentation
Is phenol red broth considered a differential media?
What are the important media components of phenol red broth?
1. It is purchased as a base broth that allows one to add any single carbohydrate for testing
2. Peptone which serves as a source of amino acids
3. Durham tube which is placed upside down in the broth to determine if a gas is produced.
The pH of the phenol red broth starts out as what which means the color of the media is what?
If the pH of phenol red broth drops to what the media turns what color?
If the pH of phenol red broth raises above what the media turns what color?
If the bacterium can ferment the carbohydrate in the phenol red broth then the media will be what color?
If the bacterium cannot ferment the carbohydrate in the phenol red broth then the media remains what color?
If the bacterium cannot ferment the carbohydrate but breaks down peptone in the media then the media will turn what color?
Both aerobic and anaerobic respiration consist of what 3 steps?
Glycolysis, the Kreb’s cycle, and the electron transport chain (ETC)
In what two steps are aerobic and anaerobic respiration identical?
Glycolysis and Krebs cycle
The difference in aerobic and anaerobic respiration during the ETC is what?
The final electron carrier
In Aerobic respiration what is the final electron acceptor?
In anaerobic respiration what is the final electron acceptor?
Non oxygen final electron acceptor (SO4^2-)(NO3-)(CO3^2-)
The electron transport chain passes electrons down a chain of molecules that alternate between becoming what?
Oxidized and reduced
For aerobes and facultative anaerobes the final electron acceptor is or can be what?
Premature electron leakage can occur in the ETC which produces what?
A bacterium must be able to break down superoxide due to its to toxicity. What enzyme breaks down superoxide?
When superoxide dismutase breaker down superoxide, it produces what toxic compound?
In order to survive when H2O2 is produced, organisms must be able to break down H2O2. What enzyme breaks down H2O2?
The presence of catalase is determined by the production of what?
In protein catabolism proteolytic enzymes (proteases) are used to break down proteins into peptides and peptides down to their basic what?
Amino acid components
Specific what break down amino acids?
What is decarboxylation?
The removal of the carbonyl group of an amino acid
What is decarboxylase?
An enzyme that catalyzes the removal of an amino acid’s carbonyl group
What coenzyme is required for decarboxylase activity?
What is a polyamine?
An organic compound with 2 or more primary amino (NH2) groups
Why are polyamines important?
-have role in the regulation of gene transcription and translation
-have role in biofilm formation
-associated with bacterial iron scavenging molecules
-involved in the bacterial response to low pH
The presence of what can help raise the intracellular pH?
Ornithine, lysine, and arginine decarboxylases are all regulated in a bacterium and are produced specifically under what conditions?
The by-products of decarboxylase reactions are alkaline compounds that can be used to what?
Neutralize and raise the low intercellular pH
What medium is used for a decarboxylation text?
Moller’s decarboxylase base medium
What are the important components of Mollers decarboxylase base medium?
-beef extract and peptone
-pyridoxal phosphate (coenzyme required for decarboxylase activity)
-Bromcresol purple pH indicator
- media is initially between pH 5.2 -6.2 so it appears copper in color
What can be added to Mollers decarboxylase broth to test for a specific decarboxylase?
A large amount of a specific amino acid
If the decarboxylase media starts out at a neutral pH something must be done to create what?
An acidic environment
What pathway produces a large amount of acidic products that can lower the pH of media?
The decarboxylase media contains what, which many bacteria can use for fermentation?
What conditions are the most favorable to promote fermentation of glucose?
If an organism cannot ferment glucose the color of the decarboxylation media will be what?
If an organism cannot ferment glucose under anaerobic conditions in the media the organism is considered what?
If an organism can ferment glucose but the decarboxylase is not present then the decarboxylation media will turn what color?
If then decarboxylation media turns yellow the organism is considered what?
If the organism can ferment glucose under anaerobic conditions and can decarboxylase the specific amino acid then the media turns what color?
If the decarboxylation media turns purple than the organism is considered what?
The last complex of the ETC is called what?
Cytochrome C oxidase (complex IV)
In a bacterium, cytochrome oxidase specifically transfers electrons from cyctochrome c to what?
Cytochrome oxidase does what to cytochrome c and oxygen?
Oxides cytochrome c and reduces O2
What is a chromogenic reducing agent?
A chemical that can donate an electron to another molecule and in so doing undergoes a color change
What chromogenic reducing agent is used in an oxidase test?
Tetramethyl - p - phenylenediamine (TMPD)
What color does TMPD turn when it becomes oxidized?
If there is no color change during an oxidase test then the TMPD remains in a reduced form and the organism is considered what?
If the paper turns dark blue during an oxidase test then the cytochrome c oxidase was present and the organism is considered what?
TMPD is unstable so the test must be read within what?
20 to 30 seconds
If nitrate (NO3-) is used as the final electron acceptor then the bacteria can perform either what or what?
Nitrate Respiration (Denitrification) or Ammonification
What is denitrification?
A multi step process performed by a group of enzymes that leads to the production of nitrogen gas from NO3
What is ammonification?
A multi step process performed by a group of enzymes that leads to the production of ammonia from NO3
The first step of either denitrification or ammonification is what?
The reduction of nitrate (NO3) to nitrite (NO2)`
What enzyme reduces nitrate?
What is the purpose of the nitrate reduction test?
To determine if an organism can use nitrate for either denitrification of ammonification
What are the key components of a nitrate broth?
Potassium nitrate (KNO3)
A Durham tube
The broth is clear prior to inoculation
If the organism used in a nitrate test is a non fermentor as determined by a fermentation test (OF or phenol red broth) then the gas must be produced through what?
If there is gas in the nitrate reduction test then the organism is what? What is the source of gas? What is the gas?
Non-fermentor; denitrification; nitrogen gas
If an organism produces gas in the nitrate reduction test the organism is determined to be what?
Nitrate reductase positive
If the organism was determined to be a fermentor from an OF test then the type of gas produces is what?
If there is growth overnight but no gas produced or gas production occurred and organism is a fermentor, what must be added to the culture?
Sulfanilic acid and naphthylamine
After addition of sulfanilic acid and naphthuylamine the broth will turn red in color and the organism will be considered what?
Nitrate reductase positive
If the addition of the reagents to the nitrate reduction test produce no change in color what must happen?
If after reagents are added to a nitrate reduction test and there was no change in color, what can be added to catalyze the reduction of any nitrate source in the broth to nitrite?
If the broth turns red after zinc is added the organism is considered what?
Nitrate reductase negative
If after zinc is added to the nitrate reduction test there is no change in color, then the organism is considered what?
Nitrate reductase positive
What test determines whether a bacterium can perform mixed acid fermentation?
Methyl Red Test (MR)
What test determines whether a bacterium can perform 2,3-butanediol fermentation?
Votes Proskaur Test (VP)
Mixed acid fermentation produces what acids?
MR and VP broths are the same and consist of what components?
Peptone, acts as a source of proteins
Phosphate buffer which maintains the media at a neutral pH at low amounts of acid.
If after several drops of MR are added, at a pH of 4.4, the color will be what?
If after several drops of MR are added at a pH of 6.2 the color will be what?
If a bacterium can not perform mixed acid fermentation only a small amount of acid is produced so the color will be what?
If bacterium can perform mixed acid fermentation, large amounts of acids are produced and the methyl red indicator will be what color.
In 2,3-butanediol fermentation pyruvate is converted to what first and what second?
First acetoin and then 2,3-butanediol
Why cant a pH indicator be used to detect 2,3 - butanediol fermentation?
The acidic compounds quickly convert to neutral alcohols
The VP test detects what?
What two reagents are added to detect acetoin?
Alpha-naphthol and potassium hydroxide
When the reagents are added in the presence of acetoin what is produced?
What color does the media turn if diacetyl reacts with guanidine form the peptone in the media?
If no acetoin is present the color produced at the surface of the culture will be what color?
What are used to determine if a bacterium can survive and grow in the presence of a single carbon source or nitrogen source?
Nutrient utilization test
In a citrate utilization test what is used as the only carbon source and what is used as the only nitrogen source?
Citrate; ammonium phosphate
Citrate can enter the bacterium through the action of what enzyme?
Once inside the cell citrate is broken down into what by what enzyme?
Oxaloacetate and acetate; citrase
Oxaloacetate is then converted to what which can be further broken own to produce energy?
Ammonium phosphate is converted to ammonia and ammonia by-products which are all what?
What are the components of Simmons Citrate Agar
1. Defined media
2. Only carbon source is citrate
3. Only nitrogen source is ammonium phosphate
4. Contains pH indicator (bromothymol blue)
The initial color of a neutral citrate agar is what?
If the citrate agar increases to a pH of 7.6 what color does it change to?
In a citrate utilization test, if there is no growth, no pH change the media will be what color and what does that mean the organism is defined as?
Green; citrate negative
If the organism grows but the media remains green during a citrate utilization test, then the organism is considered what?
If the organism can utilize the nitrogen source then it will grow on the on the slant and the media turns what color? What is the organism defined as?
Blue; citrate positive
What is deamination?
The removal of the amine group from an amino acid
What is deaminase?
An enzyme that catalyzes the removal of an amino acid’s amine group
Specific deaminases act on specific what?
The removal of the amine group can produce what?
Pyruvate; acetyl-CoA; Krebs cycle intermediate compounds
Each of these products can be used to generate energy
Deamination reaction requires what?
The co-enzyme pyridoxal phosphate
Products of tryptophan deamination are what?
Pyruvate, ammonia and indole
what does an indole test use to determine whether a specific product has been made
What reagent is added to determine the presence of indole?
If indole is present, the color will change to what?
Red and will be along the surface
What components are used for the indole test broth?
Tryptone broth, consisting of amino acid produced front he break down of proteins by the enzyme trypsin
High concentration of tryptophan
Does not contain pH indicators
If an organism does not possess tryptophanase, then what is missing?
Red rosindole dye
IMViC tests are typically used to differentiate between what?
Enteric bacteria and/or coil forms
If indole and MR are negative, VP is either negative or positive, and citrate is either negative or positive what kind of bacteria is present?
If Indole and VP are negative but MR is positive and Citrate is either positive or negative what type of bacteria might you have?
If indole is negative, MR and VP are positive, and Citrate is either negative or positive then the type of bacteria might be what?
If the indole and MR tests are positive, the VP negative, and the citrate either positive or negative the bacteria may be what?
What is starch?
An extremely large polysaccharide made up of glucose molecules linked by glycosidic bonds to form very long chains
What are the two types of molecules that make up the structure of starch?
Amylose and amylopectin
Amylose is what?
A long chain of glucose molecules
What is amylopectin?
Branded chains of glucose molecules
What enzyme breaks down glycosidic bonds?
What is the content of starch agar?
If bacteria have alpha-amlyase it will do what on the starch agar?
Secret it and diffuse into the agar
Iodine reacts with starch to produce what color?
Iodine does not react with what?
If the agar around the bacteria still contains starch and is what color, the organism is determined to be what?
Dark brown/black; alpha-amylase negative
If the agar around the bacteria does not turn dark brown/black the the organism is considered what?
What contains between 200 and 220 amino acids?
Casein is what type of protein?
There are 4 different types of casein which account for what percentage of the proteins found in cow’s milk?
What enzyme breaks down casein?
When secreted, casease can break the peptide bonds between what?
Adjacent amino acids
What is the component for milk agar?
Powdered nonfat milk
If there is not a color change on the milk agar the bacteria is determined to be what?
If there is a zone of clearing around the bacteria on a milk agar then the bacteria is determined to be what?
What is collagen?
A protein found mostly in fibrous tissues
What is gelatin?
Product from the hydrolysis of collagen
Gelatin is an abundant source of what?
What enzyme breaks down gelatin?
Gelantinase (a proteolytic enzyme)
What is the media used in the gelatinase test?
If the media remains solid after inoculation during a gelatinase test, the organism is determined to be what?
If the growth media becomes liquified during a gelatinase test the organism is determined to be what?
What is urea?
The product of the decarboxylation of certain amino acids
What is urease?
An enzyme present in certain bacteria that can hydrolyze urea into ammonia and CO2.
Because it is a basic compound, ammonia can do what within the bacterium?
Neutralize the acidic conditions
What are the important components of a urea broth?
A trace amount of yeast extract
Potassium phosphate (buffer)
Phenol red pH indicator
If the broth remains peach or slightly yellow during a urease test, the organism is determined to be what?