1. Explain the toxic effect of O2 on strict anaerobes.
With the absence of synthesis catalase, peroxidase, or superoxide dimutase, the toxic concentration of H2O2 cannot be degraded when these organisms are cultivated in the absence of O2.
2. Illustrate the chemical reaction involved in the degradation of hydrogen peroxide in the presence of catalase.
2H2O2 ------> catalase ------> 2H2O + O2
Wednesday, April 2, 2014
Page 216- Questions 3 and 4 Lupe
3. Would
catalase be classified as an endoenzyme or an exoenzyme? Explain
it would be an endoenzyme as it does
not put out into the environment, it has to have H2O2 added to it to work.
4. Account for the ability if
streptococci to tolerate O2 in the absence of catalase activity.
It means that they are facilitative anaerobes that can
survive in both environments, aerobic and anaerobic.
Tuesday, March 18, 2014
Homework chapter 22 - 25 (Due April 17th)
(Yoli) page 182 Question 1 - 4
It's done!
(Indy) Page191 question 1
In Fermentation an organic substrate serves as the final acceptor; whereas in respiration, either inorganic ion are (anaerobic) or oxygen is the final electron acceptor (aerobic).
(Indy) page 192 question 2 and 3
3)Describe a pathway used for the degradation of carbohydrates by strict anaerobes
Anaerobic organisms break down carbohydrates using the pentose-phosphate pathway. Glycolysis is used by aerobic and anaerobic organisms in energy production.
(Yaneli) page 192 question 4 and 5
4. From your experiment data, you know that P. aeruginosa did not utilize any of the carbohydrates in the test media. In this view of this how do these organisms generate energy to sustain their viability?
It may be using acetate, which is not a carbohydrate and ammonium, or some other simple organic compounds that are present in the agar, without needing to utilize the more complex carbohydrates in the test media. Regardless, it utilizes these compounds via aerobic metabolism and that is how it generates the energy it needs to sustain their viability.
5. Clostridium perfringers, an obligate anaerobe, is capable of utilizing the carbohydrates released from injured tissues as an energy source. During the infectious process, large amounts of gas accumulate in the infected tissues. Would you expect this gas to be CO2? Explain.
Probably not expect carbon dioxide to be produced as a consequence of carbohydrate fermentation, but in reality, this does occur because Clostridium has a varied fermentation pathway, some of which produces carbon dioxide.
(Yanel) page 201 question 1
1. Explain the function of the 0.1% agar in the nitrate medium.
It makes the media semi solid, which selects the organisms that are anaerobic, which is required for nitrate reduction.
It means that the bacteria had such
an active nitrate reductase it reduced the nitrate to ammonia and molecular
nitrogen gas. As a result it has a very fast metabolism for nitrate.
It's done!
(Indy) Page191 question 1
Distinguish
between respiration and fermentation
In Fermentation an organic substrate serves as the final acceptor; whereas in respiration, either inorganic ion are (anaerobic) or oxygen is the final electron acceptor (aerobic).
(Indy) page 192 question 2 and 3
2) Do
all microorganisms use pyruvic acid in the same way? Explain
No, they do not. Metabolism of pyruvate is
not the same for all microorganisms. A variety of end products results define their different fermentative
capabilities3)Describe a pathway used for the degradation of carbohydrates by strict anaerobes
Anaerobic organisms break down carbohydrates using the pentose-phosphate pathway. Glycolysis is used by aerobic and anaerobic organisms in energy production.
4. From your experiment data, you know that P. aeruginosa did not utilize any of the carbohydrates in the test media. In this view of this how do these organisms generate energy to sustain their viability?
It may be using acetate, which is not a carbohydrate and ammonium, or some other simple organic compounds that are present in the agar, without needing to utilize the more complex carbohydrates in the test media. Regardless, it utilizes these compounds via aerobic metabolism and that is how it generates the energy it needs to sustain their viability.
5. Clostridium perfringers, an obligate anaerobe, is capable of utilizing the carbohydrates released from injured tissues as an energy source. During the infectious process, large amounts of gas accumulate in the infected tissues. Would you expect this gas to be CO2? Explain.
Probably not expect carbon dioxide to be produced as a consequence of carbohydrate fermentation, but in reality, this does occur because Clostridium has a varied fermentation pathway, some of which produces carbon dioxide.
(Yanel) page 201 question 1
1. Explain the function of the 0.1% agar in the nitrate medium.
It makes the media semi solid, which selects the organisms that are anaerobic, which is required for nitrate reduction.
(Lupe) page 202 question 2 – 5
2. Explain the functions of Solutions A and B
they show whether nitrate reduction
occurred by turning red. If no color change then nitrate has remained the same.
3. If a culture does not undergo a color change on
the addition of Solutions A and B, explain how you would interpret this
results.
1- Nitrates were not
reduced
2- Nitrates were
reduced beyond the nitrite stage to ammonia or molecular nitrogen
4. Explain why the development of a red color on the
addition of zinc is a negative test
Since zinc reduces nitrates to
nitrites, a pink or red color will appear and verifies the fact that nitrates
were not reduced to nitrites by the bacteria (a negative test).
5. Discuss the relationship between an organism’s
ability to reduce nitrate past the nitrite stage and the organism’s proteolytic
acitibity.
Wednesday, March 12, 2014
Janelly's work (page 152, questions 1-6)
1.
Compare the heat sensitivity of fungal spores to that of bacterial
endospores.
- Fungal spores are more sensitive to heat than bacterial endospores. For example, fungal spores can be killed at 60 C. However, the endospores of bacillus can stand 100 C. It takes 121 C in the autoclave to sterilize things.
2.
Compare
the effectiveness of autoclaving and dry heat.
- Sterilization in an autoclave is most effective when the organisms are either contacted by the steam directly or are contained in a small volume of aqueous (primarily water) liquid. Under these conditions, steam at a pressure about 15 psi; attaining temperature (121oC) will kill all organisms and their endospores in about 15 minutes.
- Dry heat sterilization can be an effective method of sterilization, using gravity or mechanical convection ovens. Dry heat can also sterilize items that can not be sterilized in steam or chemical sterilizers, such as powders and oils, or those that are prone to rust. In addition, Dry heat can be used for glassware, as it will not score or erode the surface as, steam might do, and dry heat will not corrode or rust instruments or needles.
- Give an example of an application (use) of thermal death time.
- In order to make sure our food is sterile enough to eat, we must know the thermal death time of whatever type of microbes might be living in it. An example is, when food canning is taking place.
- In the exercise, was the thermal death time or thermal death point determined?
5.
Give an example of a nonlaboratory use of each of the following
methods to control microbial growth:
- a. Incineration: cremation of the dead
- b. Pasteurization: milk
- c. Autoclaving: metals to be inserted into surgical tools and equipment
- Define pasteurization. What is the purpose of pasteurization?
- Pasteurization is a process of heating food, which is usually a liquid, to a specific temperature for a predefined length of time and then immediately cooling it after it is removed from the heat
- Its purpose is to reduce the bacterial population of a liquid such as milk and to destroy organisms that may cause spoilage and human disease.
Lupe's Work for March 12,2014
Critical Thinking
1.
Explain why fungi and Bacillus sometimes grow
better after heat treatment.
Fungi and Bacillus are producing endospores.
Heat activates these endospores meaning the bacillus and the fungi are able to
divide and replicate because the heat has activated the endospores.
2.
The decimal reduction time (DRT) value is the
time it takes to kill 90% of cells present. Assume that a DRT value for
autoclaving a culture is 1.5 minutes. How long would it take to kill all the
cells if 10^6 cells were present? What would happen if you topped the heating
process after 9 minutes?
It will take1.5
minutes to kill 90% of the cells. Therefore, after
1.5 minutes, 10% remain. After three minutes, 1% remain. So, to figure out how
long it would take to kill a million cells, you repeatedly multiply 10^6 by 0.1
until your answer is less than 1. So:
10^6 x (0.1)^7 = 0.1
Therefore, you need 10.5 minutes of killing to kill one million cells. 7 x 1.5 minutes = 10.5 minutes.
After 9 minutes you would have:
10^6 x (0.1)^4 = 100 cells left
Therefore, you need 10.5 minutes of killing to kill one million cells. 7 x 1.5 minutes = 10.5 minutes.
After 9 minutes you would have:
10^6 x (0.1)^4 = 100 cells left
3.
Indicators are used in autoclaving to ensure
that sterilization is complete. One type of chemical indicator turns color when
it has reached a specific temperature; the other type turns when it has reached
a specific temperature and been exposed to steam. Which type of indicator
should be used?
Tape indicators will change color when the temperature hits over 120. This
indicates that the required temperature
was attained and you are unlikely to have heat-resistant spores around. This is
the best indicators to be used.
4.
A biological indicator used in autoclaving is a
vial containing 10^9 Bacillus stearothermophilus cells that is placed in the
autoclave with the material to be sterilized. After autoclaving, the vial is
incubated and examined for growth. Why is this species used as opposed to E.
coli or B. subtilis?
The
substance is used because it can withstand high temperatures which are needed
to be sterilized without the bacteria dying. It is a thermophilic which has the
presence of heat-resistant endospores.
Monday, February 24, 2014
mcb2010L Chapter 15 - 17 (due feb. 27th)
Chapter 15 page 121, page 122, 123, 124
Yoslaine Albelo
Pg. 121
Generation Time
Direct Method: Requires enumeration of Viable cells in serially diluted samples of the test culture taken at 30 Min intervals.
Direct Method: Monitors bacterial growth by estimating Turbidity. This measurements is done by using a spectrophotometer where a beam of light is transmitted through a bacterial suspension to a light sensitive detector. This change of light would be the percentage of transmission and will also give you the logarithmic expression called absorbance. This method is more useful in measuring contamination of liquids by large numbers, rather than small numbers, of bacteria. This is done at a 30 min intervals as well.
Pg. 122
Review Questions
1. Does the term growth convey the same meaning when applied to bacteria and to multicellular organism?
- No, Growth when referring to bacteria, it means an increase in the number of individual organism or and increase in the size of a population. When referring to the growth in multicellular organism, its referring to an increase in the number of cells in a single individual organism.
2. Why do Variations in generation time exist?
A) Among different species of microorganisms?
- Because in any given environment, the optimal conditions will vary between species. A fast growing bacteria have generation times of 15-20 min under optimum growth conditions, in the other hand slow growing bacteria can take up to 24 hrs under optimum condition.
B) Within a single microbial species?
- Because generation time depends on several factors, temperature, PH, etc. Growth medium can influence growth within a single microbial species.
3. The generation time and growth rate of an organism grown in the laboratory can be each determined by constructing a typical growth curve.
A) Would you expect the growth rate of the infectious organisms found in an abscess that developed from a wound to mimic the growth curve obtain in the laboratory? Explain.
- No. Lab conditions usually have plentiful nutrients and ideal growth temperature. In an abscess from a wound, the fact that the bacteria has our immune system fighting them, and that they have to search for nutrients, would definitely slow down their rate of growth.
B) Would you expect antibiotic therapy to be effective without any other concurrent treatment of the abscess?
- In most cases no. Antibiotic are often unable to get into the abscess due to the abscess wall formed by adjacent uninfected cells around the abscess to prevent the spread of infection. Usually incision and/or drainage is required.
C) Is generation time a useful parameter to indicate the types of media best suited to support the growth of a specific organism? Explain.
- Yes. Organisms with a faster generation time can often grow quickly due to their non-specific requirements for growth and will be able to grow in a variety of different media. Slow growing organisms often have very specific nutritional requirements and will need a more complex media. This can be determined by using generation time measurements.
page 123, 124 (Indy Graph)
Chapter 16 page 139
Page 140 (Lupe)
Chapter 17 page 147 (Done), 148
Janelly Carrasco, page 148
4. Which of the experimental chemical compounds appear to have the broadest range of microbicidal activity? The narrowest range of microbicidal activity?
The chemical compounds that appear to have the broadest range of microbicidal activity is bleach and hydrogen peroxide. The narrowest range was LT.
Review Questions
1. Evaluate the effectiveness of a disinfectant with a phenol coefficient of 40.
It would be 40x more effective than phenol.
2. Can the disinfection period (exposure time) be arbitrarily increased? Explain.
No, not without considering the toxicity of the chemical and environmental conditions that have to be considered before altering exposure time.
3. A household cleaner is labeled germicidal. Explain what this means to you.
This means that the antimicrobial agent is microbial. However, it does not indicate the type or types of microbes that the agent will kill effectively.
Yoslaine Albelo
Pg. 121
Generation Time
Direct Method: Requires enumeration of Viable cells in serially diluted samples of the test culture taken at 30 Min intervals.
Direct Method: Monitors bacterial growth by estimating Turbidity. This measurements is done by using a spectrophotometer where a beam of light is transmitted through a bacterial suspension to a light sensitive detector. This change of light would be the percentage of transmission and will also give you the logarithmic expression called absorbance. This method is more useful in measuring contamination of liquids by large numbers, rather than small numbers, of bacteria. This is done at a 30 min intervals as well.
Pg. 122
Review Questions
1. Does the term growth convey the same meaning when applied to bacteria and to multicellular organism?
- No, Growth when referring to bacteria, it means an increase in the number of individual organism or and increase in the size of a population. When referring to the growth in multicellular organism, its referring to an increase in the number of cells in a single individual organism.
2. Why do Variations in generation time exist?
A) Among different species of microorganisms?
- Because in any given environment, the optimal conditions will vary between species. A fast growing bacteria have generation times of 15-20 min under optimum growth conditions, in the other hand slow growing bacteria can take up to 24 hrs under optimum condition.
B) Within a single microbial species?
- Because generation time depends on several factors, temperature, PH, etc. Growth medium can influence growth within a single microbial species.
3. The generation time and growth rate of an organism grown in the laboratory can be each determined by constructing a typical growth curve.
A) Would you expect the growth rate of the infectious organisms found in an abscess that developed from a wound to mimic the growth curve obtain in the laboratory? Explain.
- No. Lab conditions usually have plentiful nutrients and ideal growth temperature. In an abscess from a wound, the fact that the bacteria has our immune system fighting them, and that they have to search for nutrients, would definitely slow down their rate of growth.
B) Would you expect antibiotic therapy to be effective without any other concurrent treatment of the abscess?
- In most cases no. Antibiotic are often unable to get into the abscess due to the abscess wall formed by adjacent uninfected cells around the abscess to prevent the spread of infection. Usually incision and/or drainage is required.
C) Is generation time a useful parameter to indicate the types of media best suited to support the growth of a specific organism? Explain.
- Yes. Organisms with a faster generation time can often grow quickly due to their non-specific requirements for growth and will be able to grow in a variety of different media. Slow growing organisms often have very specific nutritional requirements and will need a more complex media. This can be determined by using generation time measurements.
page 123, 124 (Indy Graph)
Chapter 16 page 139
Page 140 (Lupe)
Page 140
|
Chemotherapeutic Agent
|
Spectrum of Activity
|
Type(s) of Microorganisms
|
|
Penicillin
|
Narrow Spectrum
|
Gram Negative
|
|
Streptomycin
|
Broad Spectrum
|
Gram Negative and Gram Positive Bacteria
|
|
Tetracycline
|
Broad Spectrum
|
Gram Negative and Gram Positive
|
|
Chloramphenicol
|
Broad Spectrum
|
Gram Negative and Gram Positive
|
|
Gentamicin
|
Broad Spectrum
|
Gram Negative and Gram Positive
|
|
Vancomycin
|
Narrow Spectrum
|
Gram Positive
|
|
Sulfanilamide
|
Broad Spectrum
|
Gram Negative and Gram Positive
|
Review Questions
1.
Antibiotic
specially function to destroy the peptide cross-bridge of peptidoglycan (the
cell wall of bacteria). Since fungi cell wall compose of chitin, antibiotic
won't affect fungi.
Chapter 17 page 147 (Done), 148
Janelly Carrasco, page 148
4. Which of the experimental chemical compounds appear to have the broadest range of microbicidal activity? The narrowest range of microbicidal activity?
The chemical compounds that appear to have the broadest range of microbicidal activity is bleach and hydrogen peroxide. The narrowest range was LT.
Review Questions
1. Evaluate the effectiveness of a disinfectant with a phenol coefficient of 40.
It would be 40x more effective than phenol.
2. Can the disinfection period (exposure time) be arbitrarily increased? Explain.
No, not without considering the toxicity of the chemical and environmental conditions that have to be considered before altering exposure time.
3. A household cleaner is labeled germicidal. Explain what this means to you.
This means that the antimicrobial agent is microbial. However, it does not indicate the type or types of microbes that the agent will kill effectively.
Thursday, February 6, 2014
chapter 11-13 lab
Chapter 11 -
page 95
Purpose :
The purpose of acid-fast staining is to identify acid-fast organisms that belongs to genus mycobacterium.
pg 96 (Yoli)
Questions
1. What are the large stained areas on the sputum slide?
- Mainly white blood cells and non acid-fast organisms
2. What is the decolorizing agent in the gram stain?-Ethanol2b. In the acid-fast stain?
- Acid alcohol
3. What diseases are diagnosed using the acid-fast stain?
-Tuberculosis (caused by Mycobacterium tuberculosis), Leprosy, Nacordiosis.
4. What is phenol (carbolic acid), and what is its usual application?
-Phenol is an alcohol with a benzene ring attached. It s an aromatic compound and it is used as a disinfectant because it controls the growth microorganisms.
Critical Thinking!
1. Assuming you could stain any cell, would an acid-fast organism be gram-positive or gram-negative? Explain.
-It would be gram positive (a weak or abnormal gram positive) because acid-fast organism have a wax-like lipid called mycolic acid that makes them impermeable to most stains, it won't pick up the blue/purple color correctly but the color that it does pick up it won't be decolorized at all by the decolorizing agent so it would give a weak positive gram result.
2. How do the acid-fast properties relate to the gram stain?
-Acid-fast organism retain the primary stain even after the decolorizing agent, Gram-positive also retains the primary stain after the decolorizing agent and Gram-negative would lose the primary stain when washed with the ethanol. Acid-fast staining is used to differentiate between different types of bacteria, which is the same use of the gram stain.
3.Clinical specimens suspected of containing Mycobacterium are digested with sodium hydroxide (NaOH) for 30 minutes prior to staining. Why is this technique used? Why isn't this technique used for staining other bacteria?
-Its used to remove debris and contaminating bacterias. This technique cannot be used for staining other bacterias because they would be killed in the process, acid-fast bacteria have a really strong and impermeable wall and it won't be killed with the sodium hydroxide.
Chapter 12 - page 102, 103 Janelly
Chapter 113 - page 107 Lupe
2. The microscopic appearance of S. aureus is a dark purple color hue and it's shape and appearance is considered coccobacillus (a cluster of irregular cells). The appearance of E. coli is of white color hue and it is single bacillus (irregular single cells). The last one, B. cereus is of dark purple color hue and its arrangement is single bacillus.
1. No methylene blue cannot be used in place of nigrosin for negative staining. Methylene blue is is a basic stain that is positively charged. Negative staining requires an acidic stain that is negatively charged.
2. The advantages of negative staining are that it does not require heat fixing, cell is highlighted which makes it easier to see, and it is simple and quick.
3. The bacteria remains unstained, because with negative staining, the staining will occur around the organism.
page 95
Purpose :
The purpose of acid-fast staining is to identify acid-fast organisms that belongs to genus mycobacterium.
pg 96 (Yoli)
Questions
1. What are the large stained areas on the sputum slide?
- Mainly white blood cells and non acid-fast organisms
2. What is the decolorizing agent in the gram stain?-Ethanol2b. In the acid-fast stain?
- Acid alcohol
3. What diseases are diagnosed using the acid-fast stain?
-Tuberculosis (caused by Mycobacterium tuberculosis), Leprosy, Nacordiosis.
4. What is phenol (carbolic acid), and what is its usual application?
-Phenol is an alcohol with a benzene ring attached. It s an aromatic compound and it is used as a disinfectant because it controls the growth microorganisms.
Critical Thinking!
1. Assuming you could stain any cell, would an acid-fast organism be gram-positive or gram-negative? Explain.
-It would be gram positive (a weak or abnormal gram positive) because acid-fast organism have a wax-like lipid called mycolic acid that makes them impermeable to most stains, it won't pick up the blue/purple color correctly but the color that it does pick up it won't be decolorized at all by the decolorizing agent so it would give a weak positive gram result.
2. How do the acid-fast properties relate to the gram stain?
-Acid-fast organism retain the primary stain even after the decolorizing agent, Gram-positive also retains the primary stain after the decolorizing agent and Gram-negative would lose the primary stain when washed with the ethanol. Acid-fast staining is used to differentiate between different types of bacteria, which is the same use of the gram stain.
3.Clinical specimens suspected of containing Mycobacterium are digested with sodium hydroxide (NaOH) for 30 minutes prior to staining. Why is this technique used? Why isn't this technique used for staining other bacteria?
-Its used to remove debris and contaminating bacterias. This technique cannot be used for staining other bacterias because they would be killed in the process, acid-fast bacteria have a really strong and impermeable wall and it won't be killed with the sodium hydroxide.
Chapter 12 - page 102, 103 Janelly
PAGE 102 & 103
1. Why is heat necessary in spore staining?
Heat is necessary in spore staining because it is important that heat penetrates the endospore wall. Therefore, the imperiate coat that spores contain around them can loosen up the cortex and allow it to accept the stain.
2. Explain the function of water in spore staining.
The function of water in spore staining is to decolorize the vegative components. It also washes off the excess primary stain, but not the spore.
3. A.) Tap water is normally used as the decolorizing agent to wash off excess stain. When using acid-alcohol, it decolorizes the cells and results in removing the stain.
B.) When you use safranin as the primary stain and malachite green as the secondary stain, the cells will stain green.
C.) When heat is not applied during the primary stain, the spores are not stained and t hey appear colorless.
4. Explain the medical significance of a capsule.
Capsules essentially “hide” the bacteria. Encapsulated bacterial cells generally have greater pathogenicity because capsules protect the bacteria against phagocytes, so that the WBC's can't attack it. It is also used for biofilms, which can form on non-living materials in catheters, IUD's and pacemakers.
5. Explain the function of copper sulfate in this procedure.
The function of copper sulfate in this procedure is that it is used as a decolorizing agent that washes away the purple primary stain out of the capsule.
Show less1. Why is heat necessary in spore staining?
Heat is necessary in spore staining because it is important that heat penetrates the endospore wall. Therefore, the imperiate coat that spores contain around them can loosen up the cortex and allow it to accept the stain.
2. Explain the function of water in spore staining.
The function of water in spore staining is to decolorize the vegative components. It also washes off the excess primary stain, but not the spore.
3. A.) Tap water is normally used as the decolorizing agent to wash off excess stain. When using acid-alcohol, it decolorizes the cells and results in removing the stain.
B.) When you use safranin as the primary stain and malachite green as the secondary stain, the cells will stain green.
C.) When heat is not applied during the primary stain, the spores are not stained and t hey appear colorless.
4. Explain the medical significance of a capsule.
Capsules essentially “hide” the bacteria. Encapsulated bacterial cells generally have greater pathogenicity because capsules protect the bacteria against phagocytes, so that the WBC's can't attack it. It is also used for biofilms, which can form on non-living materials in catheters, IUD's and pacemakers.
5. Explain the function of copper sulfate in this procedure.
The function of copper sulfate in this procedure is that it is used as a decolorizing agent that washes away the purple primary stain out of the capsule.
Chapter 113 - page 107 Lupe
2. The microscopic appearance of S. aureus is a dark purple color hue and it's shape and appearance is considered coccobacillus (a cluster of irregular cells). The appearance of E. coli is of white color hue and it is single bacillus (irregular single cells). The last one, B. cereus is of dark purple color hue and its arrangement is single bacillus.
1. No methylene blue cannot be used in place of nigrosin for negative staining. Methylene blue is is a basic stain that is positively charged. Negative staining requires an acidic stain that is negatively charged.
2. The advantages of negative staining are that it does not require heat fixing, cell is highlighted which makes it easier to see, and it is simple and quick.
3. The bacteria remains unstained, because with negative staining, the staining will occur around the organism.
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