Microbiology Lab 1-7 Midterm Review

entero-

intestines

-osis

abnormal condition

-phage

virus

retro-

backwards

pneumo-

lung

myc(o)-/mycet(o)

fungi/fungus

baterio-/-bacter

relating to bacteria

vir(o)/vir

relating to virus

adeno-

relating to gland

gono-

relating to reproducive sys

meningo-

relating to meninges

strepto-

chain

spirillum/spirochete

 

spiral

staphylo-

cluster

vibrio

curved rod

diplo

two/pair

-coccus/-cocci

 

round

-bacillus/bacilli

 

rod shaped

Who was the first person to view bacteria using a microscope?

Antonie van Leeuwenhoek

coarse adjustment (focus) knob

roughly focuses the specimen using larg increments

condenser

lenses that sharpens light into a precise cone to illuminate specimen

light souce (lamp)

iluminates the specimen

ocular lens

the lens closest to the eye; specimen magnification

fine adjustment (focus) knob

focuses the specimen into small increments

stage

part where specimen slide is placed

objective lens

lens closest to the specimen; specimen magnification

The area of the specimen seen though the microscope is called ____________.

 

the field of view

The amount of detail you can see (the sharpness of the image) regardless of the specimen magnifications is ______________.

resolution

When switching from a lower power objective lens to a higher power one, what must be done to correct the contrast?

open the iris diaphragm to let in more light

Order the steps you follow when examining a bacterial sample with the compound light microscope.

1) add immersion oil
2) focus the slide with the 10x objective
3) focus the slide under the lowest power (4x) obejctive with the coarse focus knob
4) focus the slide with the 100x objective
5) focus the slide with the 40x objective

3, 2, 5, 1, 4

You have rotated the 10x objective into position and are ready to focus the image at 100x magnification. To do so, you should use the 

 

fine focus knob only

When you place a slide on the microscope stage, the slide clip should

hold the slide in place by gripping its edges

What part of the microscope is used to center the specimen in the middle of the field of view?

coaxial stage controls

When using a compound light microscope, as the magnification increases, the field of view

decreases

When viewing a slide of bacteria, you change to a total magnification of 1000x and you find you cannot bring the image into clear focus and that the image is dark with low contrast. Which of the following represents something you should check. Select ALL that apply.

adjust the iris diaphragm to increase the contrast.

check that you added immersion oil.

check that the 100x objective lens is touching the immersion oil.

You changed from the 10x objective lens to the 40x objective lens and suddenly the field of view went totally black. What is the most likely reason why this happened?

the objective lens is not locked into the correct position

You have been instructed only to use the coarse focus knob when initially focusing with the 4x objective. But another student questions this rule, claiming that the coarse focus lets you focus more quickly with most objectives. The following statements apply to using the coarse focus with higher objectives. Select ALL that apply. 

using the coarse focus could cause you to damage the objective lens.

using the coarse focus could cause you to crack your slide

A classmate is having trouble viewing a bacterial sample at a total magnification of 400x. The sample is very blurry and cannot be focused. The specimen looks like it is being viewed through a layer of vaseline. What does this problem indicate?

the 40x objective lens accidentally got immersion oil on it

When carrying a microscope which of the following should you NOT hold it by? Select all that apply.

only the arm

only the base

arm and stage

base and stage

only the stage

Why is immersion oil used when viewing a specimen with the 100x objective lens?  

it prevents the scattering of light away from the objective lens

What is the total magnification of a specimen if you are using a compound light microscope with the 40x objective lens?

400x

You are viewing a specimen using the 100x objective, but the image is fuzzy.  Assuming that the microscope is clean and functioning properly, what is the likely reason why the image isn’t clear?

you forgot to use immersion oil

True or False? All types of bacteria will grow in general nutrient media such as tryptic soy broth (TSB) and tryptic soy agar (TSA).

False

True or False? A microbiologist knows the exact composition of complex media.

False

What would be the best form of TSA media used to grow anaerobic bacteria?

TSA deep

What would be the best form of TSA media used to transport organisms from the hospital to the Lab?

TSA slant

What would be the best form of TSA media used to assess bacterial mobility?

TSA semi-solid

What would be the best form of TSA media used to separate different species of bacteria from a mixed culture?

TSA plate

What is the best temperature to store bacterial cultures for up to a month?

 

4 degrees Celsius

What is the best way to store cultures for over one month?

 

cryopreserved (frozen)

What is the term for taking a sample of stock culture or patient specimen and transferring it to fresh medium on which the microbes can grow?

inoculation

Why do we flame an inoculating loop if it hasn’t be exposed to bacteria yet?

dust in the air could have contaminated the loop

Why would aerosolization of bacteria be a concern?

bacteria could contaminate your workspace

Which of the following could possibly lead to contamination when transferring a stock culture to fresh nutrient media? Select all that apply

 

sneezing

 

dust in the air of the lab

 

an inoculating loop that was not flamed

A researcher wants to observe colony morphology of a bacterial culture. Which medium would be the most appropriate to use?

agar plate

A researcher wants to culture large quantities of bacteria. Which medium would be the most appropriate for this task?

broth

Why is it important to wait for the loop to cool before obtaining an inoculum. Select all that apply

to prevent burning the media with the hot loop

to avoid heat-killing the bacteria as you insert the hot loop into the liquid culture media

to avoid aerosolizing the bacteria, which could lead to contamination

True or False? When labeling an agar plate, the lid should be labeled.

False

The Bunsen burner is lit and you have labeled your uninoculated media. What is the next step in aseptic technique?

sterilize the inoculating loop

You have just obtained an inoculum from a stock broth culture of Serratia marcescens to be aseptically transferred to an agar plate. What should to do next?

flame the lip of the tube

You have just uncapped a test tube containing fresh nutrient broth. What should you do next?

sterilize the lip of the broth test tube in the flame

A patient’s sample was contaminated with Coccidioides, a soil fungus. At what point could the patient’s sample been contaminated? Select all that apply

during sample collection when the lid was off the tube

when the sample was opened in the lab

when the sample was transferred to culture media in the lab

Which of the following is a possible outcome if aseptic technique is not used in a clinical laboratory? Select all that may apply

a patient sample may give a false-positive result, leading to an incorrect diagnosis and possible incorrect treatment plan for the patient

 

samples and/or culture media may become contaminated with unwanted microbes

 

time and money would be wasted since contaminated media must be discarded and diagnostic tests would have to be repeated

 

a lab technician may inadvertently become contaminated with lab microbes and fall ill

A nervous intern just started a position in a research laboratory. The intern sets an inoculating loop on the benchtop after transferring a pathogenic strain of Pseudomonas aeruginosa into nutrient broth. Unfortunately, the intern forgot to flame the loop after inoculating the broth. Unknowingly, a coworker grabs the loop with an ungloved hand, places it in the loop holder, and then sets a lab notebook on the bench. Which of the following is a possible outcome in this situation? Select all that may apply

 

transfer of P. aeruginosa to the coworker's lab coat leading to contamination of other areas of the lab

 

contamination of the lab notebook with P. aeruginosa

 

the coworker could develop an infection if P. aeruginosa enters any breaks in the skin

When a patient is suspected of having meningitis, a sample of spinal fluid is taken and tested in the laboratory. Normally, spinal fluid is sterile, so if bacteria grow after the sample has been inoculated on media, the doctor knows that it is a bacterial infection and antibiotics must be prescribed. If there is no bacterial growth, a viral infection is usually suspected, and supportive therapies are provided to help alleviate symptoms. For a patient with bacterial meningitis, which of the following steps is most important for avoiding a misdiagnosis of viral meningitis?

do not flame the inoculating loop after the sample has been obtained

Identifying contamination of an agar slant or agar plate is somewhat easy because you can see the differences of colonies on the surface. But how could you identify contamination in a nutrient broth culture after inoculation and incubation?

Actually, unless you distinctly remember breaching the aseptic protocol, identifying contamination in a broth culture is not really possible.

Which of the following scenarios would result in no growth on nutrient media? Select all that apply

agar plate lid inoculated instead of the agar surface

loop not properly cooled

loop flamed after collecting bacteria AND before inoculating media

Which of the following scenarios would result in possible contamination of growth on nutrient media? Select all that apply

loop not flamed prior to collecting bacterial inoculum

agar plate lid is left completely open during the entire inoculation procedure

Which of the following scenarios would result in expected growth on nutrient media? Select all that apply

 

loop flamed until red hot, then cooled 20 seconds prior to obtaining bacterial inoculum

True or False? Antiseptics are chemicals that can be used on living tissue to limit microbial numbers.

True

A researcher grabs a tube of fresh nutrient broth and notices the media is cloudy and has a red hue. How should the researcher proceed?

obtain a new tube of fresh media

A laboratory technician in a diagnostic lab notices multiple colony types with different colors on an agar plate. What could cause this result?

multiple bacteria in the patient sample

 

improper aseptic technique

 

contamination of the media

A laboratory supervisor asked a technician to transfer a stock culture to an agar slant. If the technician accidentally flamed the loop right before inoculating the slant, what would be the result?

The stock bacteria on the slant would not grow

True or False? The transfer of genetic material from parents to their offspring is called horizontal gene transfer.

False

Two organelles that are theorized to have evolved from prokaryotic cells are ______________ and _________________.

mitochondria; chloroplasts

True or False? Organisms in domain archaea are more closely genetically related to organisms in domain bacteria than domain eukarya.

False

Which of the following support the endosymbiotic theory of mitochondria and chloroplast evolution? Select all that apply.

mitochondria and chloroplasts have 70S ribosomes

 

mitochondria and chloroplasts have a single double-stranded circular chromosome

What molecule is a component of both Gram-positive and Gram-negative bacterial cell walls?

peptidoglycan

Organisms in domain archaea have cell walls that contain _______________.

pseudopeptidoglycan

Many extremophiles such as halophiles, thermophiles, and acidophiles belong to domain _______________.

archaea

Prokaryotes reproduce asexually mainly by a process called ____________.

 

binary fission

A patient presents with nausea and diarrhea, and informs you that he was recently in Africa and drank water from a stream. Tests for various parasitic infections were negative, so the illness is likely caused by a bacterial infection. After further testing the patient is diagnosed with chlorea caused by the bacterium, Vibrio cholerae. Using the information ascertained from the bacteria's name, what shape do you think this organism is?

comma shaped

Using your knowledge about the charge of various bacterial cellular components, predict what charge an acidic dye has. 

the ion is negatively charged

examples are crystal violet and methylene ble

basic dye

stains microbial cells

basic dye

colorful portion of the dye is negatively charged

acidic dye

colorful portion of the dye is positively charged

basic dye

examples include nigrosin and India ink

acidic dye

repelled by microbial cells

acidic dye

Put the steps of making a bacterial smear from a broth culture then simple staining the sample in the order they occur.

1. spread the cells n a clean slide

2. air dry the smear

3. heat fix the smear

4. flood smear with methylene blue

5. rinse smear with deonized water

6. blot the slide dry

Which of the following actions should be taken when preparing a bacterial smear for staining with a basic dye? Select all that apply.

 

air-dry the smear completely prior to heat-fixing

cool the wire loop sufficiently after flame sterilization prior to taking your bacterial sample

Your medical laboratory receives a clinical specimen from a patient believed to have inhalation anthrax. Your lab assistant has stained the specimen with methylene blue and observes rods arranged in chains. Which of the following arrangements best describes the observed cellular shape and arrangement?

streptobacilli

You are preparing a bacterial smear from a broth culture for simple staining. You just spread a loopful of cells on a glass slide. What is the next step in the process?

air-dry the slide

Your clinical lab technician misplaced the stock of methylene blue. The technician want to stain the cells directly and asks if it would be acceptable to substitute acid fuchsin, an acidic dye, for methylene blue. Would this be an acceptable substitution?

No, methylene blue is a basic dye which stains cells and acid fuchsin is an acidic dye that stains the background.

Your eager lab partner decides to skip the step of resuspending the cells in a broth culture tube, saying, "I see a sediment at the bottom of the tube; I will just pick up cells from there." How should you respond?

 

 

Resuspending the culture ensures even sampling and appropriate smear thickness.

Correctly order the procedural steps in the left-hand column to indicate how the inoculum to prepare a smear is aseptically obtained.

1. uncap culture tube

2. flame sterilize tube lip

3. obtain one loopful of culture

4. flame sterilize tube lip and recap tube 

5. replace tube

You just transferred one loopful of inoculum to a slide. What would be the likely result if you added several more loopfuls of culture. Select all that apply.

Heat-fixation may be inadequate for some cells, resulting in staining inconsistencies.

 

Cell layering would make cellular morphology more difficult to determine.

How is a solid culture smear preparation different from a broth culture smear preparation?

water must first be added to the slide

You are preparing a bacterial smear from a solid culture for simple staining. You just transferred deionized water onto the glass slide. What should you do next?

 

flame sterilize and cool the loop

Your impatient lab partner doesn't want to wait for the slide to fully dry before heat-fixing the specimen. What do you advise?

Skipping the air-drying step may cause the cells to boil, distorting their morphology.