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Microbiology Lab
Lab 4
| Question | Answer |
|---|---|
| In order to study bacteria in the laboratory they must first be _______ or _______ on a growth media. | In order to study bacteria in the laboratory, they must first be grown or cultured on a growth media. |
| The two forms of microbiological media: | The two forms of microbiological media are liquid and semi-solid (gel). |
| A liquid form of media is referred to as a _______ medium. | A liquid form of media is referred to as a broth medium. |
| A semi-solid media is referred to as an _______ medium. | A semi-solid media is referred to as an agar medium. |
| Agar is a derivative of: | Agar is a derivative of Japanese seaweed. |
| Agar, the derivative of Japanese seaweed, is usually used as the _______ agent. | Agar, the derivative of Japanese seaweed, is usually used as the solidifying agent. |
| True or False: In its natural form, agar, the derivative of Japanese seaweed, is usually used as the solidifying agent and is non-nutritive. | True |
| _______ material when mixed with _______ and certain _______, provides a semi-solid media that will support the growth of many types of microorganisms | Agar material when mixed with water and certain nutrients, provides a semi-solid media that will support the growth of many types of microorganisms. |
| _______ grams of agar with suitable nutrients in _______ _______ of water will produce an agar medium. | Fifteen grams of agar with suitable nutrients in one liter of water will produce an agar medium. |
| Agar is much more suitable as _______ agent than as a _______. | Agar is much more suitable as a solidifying agent than as a gelatin. |
| The two main reasons why agar is much more suitable as a solidifying agent than a gelatin: | 1. Because as a gelatin, agar liquefies above room temperature. 2. Because once liquefied, it is easily attacked by many microorganisms |
| While there's been two "types" of microbiological media identified in the lab manual (liquid and semi-solid [gel]), these "types" fall into three "categories" of microbiological media: | 1. Nutrient media 2. Differential media 3. Selective media |
| What is a nutrient medium? | It's any medium that will support and maintain the growth of a wide variety of microorganisms. |
| Nutrient media provides a _______ and _______ source plus a favorable _______. | Nutrient media provides a carbohydrate and nitrogen base, plus a favorable pH. |
| Two examples of nutrient media: | Two examples of nutrient media are nutrient agar and nutrient broth. |
| Define the term fastidious | Fastidious refers to a state of being excessively particular, or hard to please. |
| Some microbes are fastidious in their food requirements and must therefore be supplied with what? | Not only a basic nutrient media but also one which has "enriched" by the addition of certain specific requirements. |
| Give an example of an enriched medium. | Blood agar is an example of an enriched medium. |
| Blood agar is merely a nutrient agar to which this has been added (type and amount)... | Blood agar is merely a nutrient agar to which 5% human blood has been added (other animal types may be used). |
| Since blood makes agar highly enriched, it is suitable for cultivating many of the more fastidious microorganisms that include? | Since blood makes agar highly enriched, it is suitable for cultivating many of the more fastidious microorganisms that include human pathogens. |
| What is a differential medium? | A differential medium is a medium that will sustain the growth of a large number of microorganisms, but in so doing will differentiate one type from another. |
| Two examples of differential media include... | Two different types of differential media include MacConkey's and EMB. |
| What type of media is EMB, and what does "EMB" stand for? | EMB is a differential medium (EMB standing for: "Eosin Methylene Blue" agar). |
| What is "eosin"? | Eosin is a red to brown sodium or potassium salt especially used as a biological stain for cytoplasmic structures. |
| How does differential media get its differential properties? | Differential media is a microbiological media to which certain dyes and indicators have been added to give the media differential properties. |
| What type of media differentiates between those gram-negative bacilli that ferment lactose and those that do not? | MacConkey's agar differentiates between those gram-negative bacilli that ferment lactose and those that do not. |
| Define fermentation | Fermentation can be defined as, any group of living organisms, such as yeast, mold, and some bacteria, that through use of enzymes, convert sugar to ethyl alcohol. |
| Give an example of fermentation. | An example of fermentation is, yeast enzymes converting grape sugars to ethyl alcohol. |
| Since MacConkey's agar is a differential medium that differentiates between gram-negative bacilli that ferment lactose and those that do not, what observation is made which differentiates the two? | Gram-negative bacilli that are lactose fermentors appear as brick red colonies while the non-lactose fermentors are colorless. |
| A type of differential medium, what does EMB agar differentiate? | EMB agar differentiates between coliform and non-coliform organisms. |
| What is a coliform organism? | Coliform organisms are gram-negative, rod-shaped bacteria normally present in the intestines. |
| Provide an example of a common coliform bacteria. | Escherichia coli (E. coli). E. coli is a colon bacillus. |
| Coliform organisms are gram-negative, _______ forming bacilli that ferments _______... | Coliform organisms are gram-negative, non-spore forming bacilli that ferments lactose... |
| When coliform organisms ferment lactose, what is produced; in how long; and at what temperature? | A coliform organisms ferments lactose with acid and gas production occurring in forty-eight hours at 35 degrees Celsius (98 degrees Fahrenheit). |
| What visual appearance do coliform organisms have when found on EMB? | Coliform organisms appear as metallic green colonies on EMB. |
| If one were to use lactose broth and Durham inverted tubes in presumptive testing, what would he be testing for? | If one were to use lactose broth and Durham inverted tubes in presumptive testing, he would be testing for enteric organisms. |
| When performing presumptive testing for enteric organisms, you're testing the ability of what, to do what? | When performing presumptive testing for enteric organisms, you're testing the ability of coliforms to form gas from sugar. |
| provide the full definition of a coliform organism. | A coliform organism may be defined as a gram-negative, non-spore forming bacilli that ferments lactose with acid and gas production in forty-eight hours at 35 degrees C. Coliform organisms appear as metallic green colonies on EMB. |
| How may a media be made selective? | A media may be made selective by the addition of various dyes, antibiotics, or other chemical compounds. |
| How does a selective media work? | By adding various dyes, antibiotics, or other chemical compounds, certain media may be made to inhibit selectively the growth of some microorganisms, while permitting the growth of others, specifically, if they are present. |
| Define the term bacteriostatic. | Bacteriostasis (bacteriostatic) is the inhibition of the growth of bacteria without destroying it. |
| Brilliant green dye is bacteriostatic to what? | Brilliant green dye is bacteriostatic to gram-positive bacteria. |
| Since brilliant green dye is bacteriostatic to gram-positive, and its addition to a media makes the media "selective," the presence of what specific microorganism is being tested? | Gram-negative, non-spore forming bacilli - more specifically, the test assesses the Since brilliant green dye is bacteriostatic to gram-positive, and its addition to a media makes the media "selective," the presence of coliform organisms (enteric bacteria |
| How would the inclusion of brilliant green dye to the confirmatory media, BGB broth, make the media selective, enabling it to culture for coliform bacilli? | Since coliform bacilli are gram-negative, and brilliant green dye is bacteriostatic to gram positive, that is, it inhibits the growth of gram-positive bacteria without destroying the gram-negative bacteria, if coliform bacilli are present, they will colon |
| The inclusion of brilliant green dye, a dye bacteriostatic to gram-positive bacteria, in the _______ media, _______ _______, is used to culture for the presence of coliform bacilli. | The inclusion of brilliant green dye, a dye bacteriostatic to gram-positive bacteria, in the confirmatory media, BGB broth, is used to culture for the presence of coliform bacilli. |
| What type of test may be used as an indicator of pathogenic staphylococci? | The coagulase test may be used as an indicator for the pathogenic staphylococci. |
| In the coagulase test, how is the presence S. aureus determined? | If after having been inoculated with bacteria, a tube of plasma coagulates, the test is positive for the presence of S. aureus - which produces the coagulase enzyme - an enzyme that reacts with factors in the plasma to initiate clot formation. |
| When activate (cleaved), what does plasminogen (a plasma protein) become? | When the plasma protein, plasminogen, is cleaved (activated), it becomes plasmin. |
| What is plasmin? | Plasmin is a protein splitting enzyme - formed after plasminogen is cleaved - which destroys fibrin and other plasma proteins. |
| Does plasminogen ever activate to form fibrin, through normal mechanisms? Explain. | Normally, the plasma protein, plasminogen, is activated when certain normal events occur, causing it to (once activated) form plasmin, which is a protein splitting enzyme that destroys fibrin and other plasma proteins. |
| How does the bacterium S. pyogenes (streptococcal pyogenes)activate plasminogen? | Instead of waiting for plasminogen to become activated by other host proteins through normal mechanisms, which would form plasmin, S. pyogenes binds to the plasminogen, and once bound, it secretes streptokinase - an enzyme that cleaves plasminogen - causi |
| By definition, any isolate that coagulates plasma is...? | By definition, any isolate that coagulates plasma is S. aureus, because all other bacteria are coagulase negative. |
| Is Streptococcus pyogenes (S. pyogenes) gram-positive or gram-negative? | S. pyogenes is gram-positive. |
| Is Staphylococcus aureus gram-negative, or gram-positive? what's it look like under a microscope? | Like S. pyogenes, it's gram-positive. both S. pyogenes and S. aureus are spherical (coccus). S. aureus looks like clusters of grapes. |
| What type of hemolytic is S. pyogenes on blood agar? | It's B-hemolytic (beta hemolytic) |
| What is a hemolysin; and what is it a product of? | A hemolysins are products of metabolism (metabolites)that have the ability to destroy red blood cells. |
| When checking for hemolysins, what bacterium is present if hemolysins are present; and what type of medium is used in the test? | Hemolytic activity indicates pathogenicity of streptococci. The test is done on blood agar, which is basically 5% whole blood. |
| Organisms inoculated on blood agar may affect it in one of three ways. They are? | 1. Alpha hemolysis 2. Beta hemolysis 3. Gamma hemolysis |
| If hemolysins are present, but only partially lyse the red blood cells, what type of hemolysis is this; and what characteristic would it have on blood agar? | This would be alpha hemolysis. Alpha hemolysis would produce a greenish zone around the colonies. |
| Explain beta hemolysis and the characteristics it'd have on blood agar. | Beta hemolysis is a complete lysing of red blood cells, which would leave a clear zone around the colonies. |
| Explain gamma hemolysis and the characteristics it'd have on blood agar. | In gamma hemolysis, there really is no hemolysis, which would have no zone around the bacteria. |
| Generally, _______ that are beta hemolytic are most virulent and are usually associated with acure _______ _______. | Generally, Streptococci that are beta hemolytic are most virulent and are usually associated with acute fulminating infections. |
| Is hemolysin production confined to Streptococci? | Hemolysin production is NOT confined to Streptococci. |
| Procedure I of lab number 4 involved checking for hemolysis on blood agar plates that had already been inoculated so that students could observe them. What three types of inoculates were used (one on each separate plate). | In procedure I of lab 4, the three bacteria used were: 1. S. pyogenes 2. S. faecalis (Streptococcus faecalis) 3. S. mitis (Streptococcus mitis). |
| The second procedure in lab 4 involved doing what type of swab? | The second procedure in lab 4 involved doing a throat swab. |
| Document the procedure used in procedure II of lab 4, when the throat swab was done. | 1. We used a sterile swab on the back of our throats 2. We then inoculated a blood agar plate. 3. After inoculating the plate, we incubated it at room temperature for one week. 4. The following week, we examined the plate looking for signs of he |
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bkachaylo
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