MIC 206 Pre-lab quizzes
Bacterial spores have a very thick protective covering called a spore coat, which makes the spore impermeable to many molecules, including many of the stains. How can the spores be stained if they are impermeable to many compounds?
The primary dye is driven into the spore by the application of heat
The transformation procedure we used in the lab did NOT involve
damaging the cell wall by calcium chloride treatment
Which of the below can influence the size of the zone produced around the antibiotic disks that are used with the Kirby-Bauer tests? Select all that apply.
depth of the culture medium rate of diffusion of the antibiotic the pH of the medium the incubation temp the concentration of the antibiotic.
The MacConkey Agar plate you will be using is
differential and selective for G- bacteria
The MacConkey Agar plate you will be using is
differential and selective for gram -
During preparation of a smear that will be used in a simple positive staining procedure, the immediate next step after spreading bacterial cells on a slide is to:
dry the smear
An organism that does not produce any bubbles when a catalase test is performed on it would be classified as a strict aerobe.
false
Antibiotics that are produced by many different types of bacteria are called broad spectrum antibiotics
false
Antibiotics that are produced by many different types of bacteria are called broad spectrum antibiotics.
false
Differential media allows growth of specific bacteria and eliminates unwanted organisms.
false
Endospore production is a method of reproduction for bacteria.
false
In the Kirby-Bauer test, any visible zone of inhibition around the antibiotic disk indicates that the bacterium is sensitive to that antibiotic.
false
Indole test detects ability of bacteria to break down amino acid indole. Group of answer choices
false
Molds are eukaryotic cells and yeasts are prokaryotic cells.
false
Most often, the trophozoites life stage is used for identification of cyst-forming protozoans.
false
Organisms like Mycobacteria are refered to as ""acid-fast"" because they prefer an acidic growth environment.
false
Proper preparation of a bacterial smear for a capsule stain involves a heat-fixation step to allow bacteria to stick to the slide without destroying the capsule.
false
Sodium thioglycolate broth medium can not be used to grow an obligate anaerobe because there is oxygen present in the bottom of the medium.
false
Streptococcus pyogenes, a group A, beta hemolytic streptococcus, will produce bubbles on a catalase test but Streptococcus pneumonia will not.
false
Urease enzyme is able to break down urea slowly upon extended time of incubation.
false
Differential media allows growth of specific bacteria and eliminates unwanted organisms.
false (a selective plate is )
All of the following can be a used to describe a possible growth pattern in broth culture except: pellicle filiform turbidity sediment
filiform
Which of the following regarding the pVIB plasmid we used is FALSE?
gives the bacteria a survival advantage when grown on plain Luria Bertani agar plates that does not contain ampicillin.
Which of the following is/are considered good aseptic technique practices?
holding the mouth of the test tube after opening the cap in front of incinerator for few seconds. opening the plate only when ready to inoculate or get the sample
What reagent will you use to perform a catalase test on an organism growing on one of your agar plates?
hydrogen peroxide
In an aqueous environment with a nearly neutral pH, the bacterial cells will carry an overall __________ charge.
negative
In the transformation experiment, you followed a procedure to transform E. coli cells with a plasmid containing an ampicillin resistance gene. After incubation, you got a "confluent lawn of growth" when the transformation mixture was spread on the Luria agar plates without ampicillin. When the same number of cells was spread over the LB plates containing ampicillin, you got only several colonies and not a confluent lawn of growth. Why?
not all of the cells picked up the plasmid and only the ones that picked up the plasmid could survive
This is an image of an E-test performed on a microorganism that was isolated from a patient. If this organism was inoculated into a test tube with media containing 0.5 microgram/ml of the antibiotic clarithromycin (Cl), it would ______________ .
not be able to grow
You want to sub-culture a bacterium that grows only at the bottom of a thioglycollate broth. You prepare a streak plate using this bacterium. Where/how would you incubate your plate?
on a plate placed in an anaerobic jar
Optical density closely correlates with number of ____________ when the culture is in the exponential phase of growth.
only the number of living cells
Which of the following tests could be used to separate Streptococcus pneumonia from Streptococcus mitis and other alpha hemolytic streptococci?
optochin susceptibility
Antibiotics are produced by all of below except
viruses
Antibiotics are produced by all of the following except: bacteria fungi viruses chemical synthesis
viruses
What would likely happen if you did not properly clean the microscope slide before making a bacterial smear?
water containing the bacteria would form beads and the bacteria would clump
Magnification is defined as the ability of the microscope to enlarge an object.What is the second factor equally important in order to view a sharp and distinct image of the specimen?
resolving power
Justin makes TSA plates to use for isolating pure cultures using the streak plating technique. The day after he realizes that he used 10 grams of dehydrated TSB powder per liter of media by mistake instead of 20 grams/liter as indicated on the bottle, but added the correct amount of water (1L) and agar (15 g/L). He continues on with streaking his plates because he doesn't have enough time to remake the media correctly. Because of this mistake, one would expect the colonies that form after an overnight incubation to be:
smaller than normal because they would run out of nutrients faster
Why should petri plates be incubated with the lid on the bottom?
so that the condensation that forms will not drop on to the bacterial growth
The application of which of the following is considered the most critical in the success of a Gram staining procedure?
the decolorizer
A countable plate is one where:
there are between 30-300 colonies
Organisms in the family Enterobacteriaceae all have these characteristics in common:
they are all gram - bacilli they all ferment glucose they do not have cytochrome c oxidase they can reduce nitrate to nitrite but do not reduce nitrite further
Which of the following is FALSE about broad spectrum antibiotics?
they are effective against a variety of bacteria and viruses
Acid-fast organisms do not take up stains easily becaue
they have large amounts of mycolic acid in their cell walls
A dimorphic fungus is one that can grow either as a yeast or mold, depending on its environment.
true
A pH indicator dye is often added in the culture medium to detect a specific biochemical reaction has happened that can be observed by change in the color of the medium .
true
A properly prepared smear should be somewhat difficult to see with the naked eye without staining .
true
An organism that produces bubbles when a catalase test is performed on it could be a strict aerobe or a facultative anaerobe.
true
Enterococcus grows on Bile Esculin media and hydrolyzes esculin, which produces a dark brown color on the media.
true
If an organism makes the enzyme catalase, it can break down hydrogen peroxide into water and oxygen which causes bubbles to be produced.
true
One can become ill with malaria if bitten by an Anophelesmosquito carrying the protozoan Plasmodium.
true
The differentiation among Gram positive cocci can be done by using : Choose all answers that apply.
type of hemolysis cell arrangement catalase rxn colony appearance
Clostridium tetani is considered an obligate anaerobe. Which of the following could be used to culture and incubate a clinical specimen in which you expect to find Clostridium tetani? Select all that apply.
In a gas pak jar in a thioglycollate broth
Iodine serves as a mordant in the Gram stain procedure. What is the best explanation of iodine's role in the Gram stain?
Iodine binds to the primary stain and forms a large crystal violet-iodine complex that becomes trapped in the cell wall.
If you place 0.5 ml of sample into 4.5 ml of water, you would be doing a __________ dilution.
1/10 (0.5/(0.5+4.5) = 0.5/5 = 1/10.)
If you place 0.1 ml of sample into 9.9 ml of water, you would be doing a __________ dilution.
1/100
In scientific notation, 1/100 dilution is written as:
10-2
The Total magnification is calculated by multiplying magnifying power of objective lens by the magnifying power of ocular lens. If the specimen is observed using oil immersion objective lens and ocular lens with 10X magnifying power. What will be total magnification?
1000x
In a standard plate count method, if you counted 34 colonies on the 10-6 plate, how many colonies would you expect to see on the 10-5 plate of the same dilution series? Type the number only in the box.
340
The optical density of cells can be best measured at a wavelength of _____________ using a spectrophotometer.
600
What is the minimum inhibitory concentration (MIC) of this antibiotic for the organism tested?
8ug/mL
Which of the colonies shown has an "entire" margin?
A
Which of the tubes of thioglycollate medium show the growth pattern of aerotolerant anaerobe bacterium ?
A A shows even growth throughout the medium suggest that they are aerotolerant anaerobe because they do not use oxygen but grow/ tolerate oxygen . They are catalase negative.
You are given the plate seen in the picture to use to observe colony characteristics . Which of the marked areas is the best to use to observe colony morphology?
B
Which of the following would you use if you were in need of an ample bacterial culture in a very short period of time?
Broth culture
Toxoplasma gondii is a protozoan that can cause severe birth defects if a woman is infected during her pregnancy. How does one get infected with Toxoplasma? Select all that apply.
By cleaning cat litter boxes and encountering the oocysts from cat feces. By ingesting undercooked hamburger that is infected
Which of these plates shows an uncontaminated culture?
C. Image downloaded
An obligate aerobe will not be able to grow in thioglycollate broth because thioglycollate eliminates all oxygen from the media.
False
Bacteria are ubiquitous. This means that microorganisms are unique.
False
In the transformation exercise we did in the lab, we selected for transformants (cells that are transformed)on LB+amp plate by their ability to glow in the dark.
False
Which of the following statement is TRUE about In the Kirby-Bauer antibiotic sensitivity test?
For anyOne has to refer to the standard reference chart to check if bacteria is sensitive even if a large zone of inhibition is obtain for antibiotic against a bacterium.
Which of the following information can be obtained from Kligler's Iron Agar? Select all that apply.
Glucose fermentation Lactose fermentation H2S gas production
Which of the following is the most accepted explanation of why some organisms stain Gram positive and others stain Gram negative? Group of answer choices
Gram negative organisms have a low peptidoglycan content in their cell walls and the crystal violet-iodine complex leaks out of their cell walls.
What reagent is added on the colonies to perform catalase test?
Hydrogen peroxide
Neisseria gonorrhea grows best in reduced oxygen concentrations and in an increased carbon dioxide environment of about 10%, but cannot grow in the absence of oxygen. How would you classify Neisseria gonorrhea?
Neisseria is a microaerophilic organism
Oxygen is essential for growth of Neisseria gonorrhea but it grows best in reduced oxygen concentrations and cannot tolerate atmospheric levels of oxygen well. How would you classify Neisseria gonorrhea?
Neisseria is a microaerophilic organism.
Which of the following step is incorrect if performed during the streak plating for isolation?
One should not sterilize the loop each time when streaking the sample on to the next quadrant ( section).
Staphylococcus aureus is coagulase positive. What media/ substance do we inoculate to determine this?
Rabbit plasma
Match the correct answers. Your colleague Jill rushes into your office as you are about to leave and asks you to quickly determine the response of this unknown organism to the antibiotics simply by looking at this picture of the KB test she performed on a patient sample. To which of the antibiotics would you tell her that this organism is resistant or sensitive? AMP CL CTT IMP
Resistant resistant cannot determine cannot determine
Bill and Bob are working on the same project involving identification of an unknown microorganism which was provided as a pure culture. Together they made one single streak plate of their unknown organism and left it in the incubator. They observed the colony morphology of their unknown organism independently of each other when they got a chance. When they got together to compile their results, they were surprised that Bill defined the colonies as white, small, circular with entire margins, while Bob defined them as orange, large, irregular with undulate margins even though there was only one type of colony on the plate. They were worried about this discrepancy because both were very careful about their observations and used dissection scopes to examine the colonies. Whose result would you believe? What would be your explanation for the discrepancy they observed? Type your answer in the text box below. (Word limit: 30 words).
Since Bill and Bob were both observing the same streak plate, but independently of each other, they must have looked at the plate on different days during the incubation period. Remember, colonies can change their characteristics significantly upon extended incubation. So, both are correct in their definitions
The Minimum Bactericidal Concentration (MBC):
The lowest concentration of an antibiotic that kills the test cells.
Why do we use special media like Sabouroud Dextrose Agar to grow fungi?
The media has a pH of 4.5-5.6 which supports fungal growth and inhibits most bacterial growth.
Which of the following is NOT true about broad spectrum antibiotics?
They are effective against a variety of bacteria and viruses
The graph shows the correlation between optical density (absorbance) of a culture and cell density in terms of CFU/ml. If you were asked to start an experiment using a culture at a concentration of 2.5 x 108 CFU/ml, to what optical density would you grow your culture? Hint: pay attention to the exponent it is asked for!
To find the answer, you would first need to convert the 2.5 x 108 to the 107-exponent equivalent, which would be 25 x 107. Since 107 is already included in the axis label, the number would be just 25. Then you would need to find 25 on the X-axis and trace it to the point where it meets the best line and find its value on the Y-axis, which in this case is about an absorbance value of 1.
A pH indicator dye is often added in the culture medium to detect a specific biochemical reaction has happened that can be observed by change in the color of the medium .
True
Bacteria acquire drug resistant gene from other bacterial cell via horizontal gene transfer.
True
For the standard plate count technique, use of the term "colony forming units (CFU)" is preferred over "number of cells" when expressing cell densities because CFU takes into account the fact that colonies could develop from single cells or from multiple cells clustered together.
True
One can identify the size, shape , and cell arrangement of bacteria by simple staining them.
True
Presence of cytochrome C oxidase enzyme in bacterial culture suggests that it has mitochondrial like ETC .
True
Two genes designated such as gene for amp resistance and a gene for luciferase enzyme are located on a single plasmid. If you selected for amp resistance gene in the growth medium, the cells will also contain gene for luciferase enzyme as a result of transformation.
True
We streak for isolation , particularly from clinical sample such as a throat swab so as to obtain a pure culture of the pathogen to be identified that most likely present as a mixed culture in the clinical sample.
True
Which of the following is NOT a true statement about a simple stain?
a simple stain involves the use of two or more dyes
Which of the below is a "pure culture" of bacteria? Select all that apply: a. a plate culture which contains only one single colony b. a liquid of solid culture vessel containing a single strain of bacteria c. a broth culture that originated from a single cell d. a plate culture containing multiple different colony types
a, b, c
You inoculate an unknown organism into a thioglycollate broth and after 48 hours you observe the growth pattern as growth only on the surface of broth in the methylene blue layer. What would this organism be classified as according to its oxygen requirement? What would be its catalase reaction if you tested it? Select one classification and one catalase reaction for full credit (caution: incorrect choices lead to points deduction).
aerobe and catalase positive
Which of the factors below can influence characteristics of bacterial colonies such as size, appearance ? age of colony location of colony type of medium and available nutrients
all the above
Protozoa are defined as eukaryotic organisms that are unicellular and have no cell wall. These organisms may use __________ for locomotion.
all the above (flagella, cilia, and pseudopods)
Which of the following bacteria are capable of producing endospores?
bacillus and clostridium
Which of the following tests can be used to differentiate Streptococcus pyogenes from other beta-hemolytic streptococci?
bacitracin sensitivity
Hemolysis can be used to differentiate bacteria. Staphylococcus aureus produces a clear zone around the bacterial colonies by secreting an enzyme that completely ruptures the red blood cells and leads to breakdown of the hemoglobin. Staphylocccus aureus usually produces a double zone of hemolysis creating a "halo" effect on the media. What kind of hemolysis does Staphylococcus aureus produce?
beta
Which of the following is NOT a property of capsules?
bind negatively charged dye
Which of the following can reduce nitrate to nitrite?
both nitrate reductase and Zn dust
In this lab the type of microscope we will be using is called a ___________ microscope.
brightfield
While Rebecca Lancefield classification of Streptococci into serological groups is based on the antigens on their cell walls (Group A, B, C, etc.). In the laboratory we also classify them initially by which of the following means?
by their type of hemolysis
If you were bitten by a tsetse fly in Africa, you could get a Trypanosoma infection that causes African Sleeping Sickness. If you were bitten by the "kissing bug" in Arizona you might get a Trypanosoma infection called
chagas disease
What is the only/ sole source carbon source present in Simmon citrate Agar?
citrate
Which of the following lens concentrates the light beam and directs it through the specimen?
condenser lens
Which of the following information can be obtained from Kligler's Iron Agar? Select all that apply.
glucose fermentation lactose fermentation H2S gas production
A bacterium that grows very well in less than 2 % salt concentration (example on regular TSA plate with 0.5% NaCl) and is also able to grow on a TSA plate containing 12 % salt is classified as a:
halotolerant
Capsules may be made up of polysaccharides, glycoproteins or polypeptides and
have no net charge
The Minimum Inhibitory Concentration (MIC):
is the lowest concentration of an antibiotic that is able to inhibit the growth of a test organism
The Minimum Inhibitory Concentration (MIC):
is the lowest concentration of an antibiotic that is able to inhibit the growth of a test organism.
What is the purpose of adding an antibiotic to the media used in the transformation exercise?
it is a way to select for the cells that picked up the plasmid
The lenses of the microscopes can be cleaned with:
lens paper only
Match the type of objective lens with the correct magnifying power.
low power objective lens: 10x High-dry objective lens: 40x oil immersion objective lens: 100x scanning power objective: 4x
If a bacterium grows at 15% NaCl concentration but does not grow below 2% NaCl concentration, it would be classified as:
moderate halophile
Part of the scientific description of these colonies includes "pink." This term describes their:
pigmentation
What color will bacteria be on a gram - stain?
pink
You will be observing several organisms on Mannitol Salt Agar during this laboratory session. What type of a medium is Mannitol Salt Agar?
selective and differential
Molds are usually identified in the laboratory by all of the below except for their:
size of colonies