When plates are incubated at 37°C, they should always be placed upside down to prevent condensation from pooling on the growing cultures.
Microscopes you will be using in lab to view your smears are:
•Delicate instruments that require care and daily maintenance
•Equipped with 100x objectives
•Compound light microscopes
Place the following in the order light travels from the light source to through the specimen (your smear) to your eye: a - light source; b - ocular lens; c - condenser; d - objective; e - smear; f - slide on the stage; g - your eye. (write your answer with no spaces or punctuation between the letters)
light source, condenser, slide on the stage, smear, objective, ocular lens, my eye
Preparing a smear is done using which of the following pieces of equipment?
inoculating loop. microscopic slide, bunsen burner or hot plate
When using the microscope, which of the following statements are true?
•You focus on the smear using the 10X objective first using the course adjustment knob.
•After you've focused with the 10X objective, you switch objectives to the 100X objective and use only the fine adjustment knob for focusing.
Which of the following most accurately describes how you should heat fix a smear if no slide warmer is available?
After letting smear air dry, quickly pass the slide over a flame
You are trying to view your simple stains using a microscope. When you are switching the objective lens from 10X to 100X, you should grab the objective lens to turn the nosepiece.
False, you should turn the revolving nosepiece to switch from the objective 10x to 100x.
In daily lab techniques and microscope care, you should follow the procedures in the lab manual. You will lose points if you:
•Clean your microscope lenses with paper towels
•Forget to clean your microscope with lens paper
•Leave your bunsen burner lit and leave the room
•Use the coarse focus with the 100X objective
What is the first thing you should do if you suspect the broth culture given to you is not a pure culture that might give you a hint that it is not pure by showing you the cell morphology or morphologies present in the culture?
stain a smear of the broth culture
You observed a stained slide under the microscope, and found some cells were random and rod shaped and the other cells were coccus shaped in chains. This smear was made from a pure culture.
If most of the cells on your smear look randomly arranged, but you find one grouping of cells that appears to be in a strepto arrangement, then this is sufficient evidence to conclude that your organism has a strepto cell arrangement.
Which of the following are used for a Gram stain?
A low agar concentration is used to test motility b/c:
Motile bacteria can move easier when agar concentrations are low
You look carefully at your simple stain of the culture for experiment 10 and see all purple rod-shaped bacteria, but some appear larger than others. You begin to think your culture is mixed. Which of following will give you more information than what you already have and help you determine if the culture is mixed?
streak plate and gram stain
Place the following in order of occurrence in performing a Gram stain: a - make a thin smear; b - cover smear with crystal violet for 1 min; c - cover smear with Gram's iodine for 1 min; d - cover with safranin for 1 min; e - heat fix the smear; f - rinse with ethanol for a few seconds; g - rinse with water; h - blot dry
make a thin smear, heat fix the smear, cover smear w/ crystal violet, rinse w/ water, cover smear w/ gram's iodine for 1 minute, rinse w/ water, rinse w/ ethanol for a few seconds, rinse w/ water, cover w/ safranin for 1 minute, rinse w/ water, blot dry
Polar flagella are attached at one or both ends of the cell, and peritrichous flagella are inserted at many locations around the cell surface.
•can be killed by autoclaving
•are problematic to the food industry b/c the bacteria that germinate and grow from the spores if ingested can produce deadly toxins.
•can survive heating, freezing, drying, exposure to various chemicals, radiation, and boiling water
Which of the following organisms did you see in lab that tested positive for motility?
In preparing the smear for the acid-fast stain, you
add egg albumin to help disperse the Mycobacterium
You did a simple stain and streak plate from a broth culture to try to determine if it is a pure culture. From what you saw you concluded the culture was pure. What information did the streak plate provide?
only one colony morphology was present
Place the organisms below in order from the hottest optimum growth temperature to coldest optimum growth temperature.
Thermophile, mesophile, psychrophile
The Bacillus cultures used for the endospore stains were grown on
slants lacking essential nutrients
Which of the following will you experimentally test for experiment 17A?
the ability of a bacterium to survive at a certain temperature for a brief period of time
To prepare your agar plate for experiment 17C you
swab your assigned bacteria over the entire agar surface
As a hospital lab technician you are given a blood culture from a patient and asked to determine if they have an active infection by Mycobacterium tuberculosis. How would you determine this?
an acid-fast stain
Describe the appearance of the Mycobacterium on a plate. With what cell component does this correlate?
compact, dry, wrinkled; mycolic acids in the cell wall
Which of the following statements regarding micropipettors is/are true?
•the pipette w/ the blue button should be used only for volumes b/t 200 and 1000ul. The pipettes w/ the gold button can accurately measure 20 - 200ul
•When picking up liquid the pipette plunger must be depressed to the first stop and slowly released. To dispense the liquid the plunger should be pushed to the first stop and then past to expel all of the liquid
•A fresh tip must be used for every transfer and the used tip must be ejected into the jar of vesphene on top of the bench
What do Bacillus sphaericus, Mycobacterium smegmatis, and Escherichia coli have in common?
A bacteria that can survive exposure to a temperature can also divide and grow at that temperature.
You are given a culture of Pseudomonas fluorescens which is psychrotolerant mesophilic bacterium to conduct experiment 17A.What temperatures do you expect it to survive?
0°C, 4°C, 37° C
Deinococcus radiodurans can survive UV exposure because it:
Has an extraordinary ability to repair its UV damaged DNA
What type of media will you be using for exp 17D?
plates with low, medium, high, very high amounts of salt
Ultraviolet radiation penetrates poorly and therefore cannot penetrate the lid of a Petri dish in order to reach the bacteria on the agar surface.
Which of the following is a disadvantage of the direct microscope count?
•it counts all cells, both live and dead.
•It requires the use of a hemacytometer
Which is the correct order of use of the three parts of the most probable number technique?
Presumptive, Confirmed, Completed
Which series of dilutions would give you an overall dilution of 10-7.
•10^-2, 10^-2, 10^-3
You will be inoculating 15 lauryl sulfate lactose broths (5 double strength and 10 single strength) for the presumptive MPN test.
You look at your plate from experiment 15 and find that your 10-4 plate contains 43 colonies. What is the cfu/ml ?
4.3 X 10^5
Which of the following statement(s) is/are true about the Most Probable Number Technique?
•Escherichia coli is used as the indicator organism for fecal contamination in the United States. •The selective component in the presumptive test is lauryl sulfate
•Coliforms ferment lactose and produce carbon dioxide within 48 hours of incubation.
•Many enteric diseases are transmitted from person to person via fecally-contaminated water.
You are using biosafety level 1 related species of 2 genera of human pathogenic bacteria for experiments 18 and 19. What are these genera?
You inoculated 1ml of a broth culture of E. coli into a bottle containing 99ml of sterile water. You then transfered 0.1ml onto a TSA plate. What is the overall dilution of that plate?
How will you prepare your plates for experiments 18 and 19?
by covering the entire surface to create a lawn of bacteria
What is the differential component in the confirmed and completed tests of the most probable number technique?
lactose in both the confirmed and completed tests
•Primary Stain - Malachite green
•"Mordant" - heat from steam drives stain into cells
•Decolorizer - water to remove stain from vegetative cells
•Counterstain - safranin
-Red vegetative cells & Green endospores
•Primary Stain - carbol-fuchsin
•"Mordant" - heat from steam drives stain into cells
•Decolorizer - acid alcohol removes the primary stain from non-acid-fast bacteria
•Counterstain - methylene blue
•does not form endospores but has radiation resistance due to incredible ability to repair DNA
•survives radiation but is sensitive to heat