Microbiology Lab 1 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 viruses

adeno-

relating to a gland

gono-

relating to reproductive system

meningo-

relating to the meninges

strepto-

chain

spirillum/spirochete

spiral

staphylo-

clusters (of grapes)

vibrio

curved rod

diplo-

two/double/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 subject in large increments

condenser

lenses that sharpen light into a precise cone to illuminate specimen

light source (lamp)

illuminates the specimen

ocular lens

the lens closest to the eye: specimen magnification

fine adjustment (focus) knob

focuses the specimen using small increments

stage

part of the microscope that the specimen slide is placed

objective lense

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) objective 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

A) check that the revolving nosepiece has the 10x objective lens locked into correct position

B) check that you added immersion oil

C) check that the 100x objective lens is touching the immersion oil

D) adjust the iris diaphragm to increase the contrast

B, C, D

You are examining a properly stained slide of bacteria at 1000x total magnification. After opening the iris diaphragm you see this pale image shown here. Which of the following explains why the cells are hard to see?

opening the iris diaphragm allowed in too much light, decreasing the contrast and lowering the resolution

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.

A) you can achieve sharp focus more quickly by using the coarse focus that the fine focus

B) using the coarse focus could cause you to crack your slide

C) the coarse focus lets you move the stage horizontally and vertically

D) using the coarse focus could cause you to damage the objective lens

B, D

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.

A) arm and stage

B) base and stage

C) only the arm

D) arm and base

E) only the stage

F) only the base

A, B, C, E, F

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?

inoculating

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

A) dust in the air of the lab

B) sneezing

C) flaming the lip of the culture tube

D) an inoculating loop that was not flamed

A, B, D

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

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

B) to prevent burning the media with the hot loop

C) to avoid aerosolizing the bacteria, which could lead to contamination

D) to avoid burning yourself

A, C

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

A) when the sample was incubated

B) when the sample was opened in the lab

C) during transport when the tube was tightly capped

D) when the sample was transferred to culture media in the lab

E) during sample collection when the lid was off the tube

B, D, E

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

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

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

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

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

ALL

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

A) transfer of P. aeruginosa to the coworker's lab coat leading to

B) contamination of other areas of the lab

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

ALL

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

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

B) agar plate lid inoculated instead of the agar surface

C) loop not flamed prior to collecting bacterial inoculum

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

E) loop flamed after collecting bacteria AND before inoculating media

F) loop not properly cooled

B, E, F

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

A) loop flamed after collecting bacteria AND before inoculating media

B) loop not flamed prior to collecting bacterial inoculum

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

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

E) loop not properly cooled

F) agar plate lid inoculated instead of the agar surface

B, D

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

A) loop flamed after collecting bacteria AND before inoculating media

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

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

D) agar plate lid inoculated instead of the agar surface

E) loop not flamed prior to collecting bacterial inoculum

F) loop not properly cooled

B

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?

A) the loop was not cooled prior to inoculation

B) improper aseptic technique

C) contamination of the media

D) multiple bacteria in the patient sample

B, C, D

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

You are examining a properly stained slide of bacteria at 1000x total magnification. After opening the iris diaphragm you see this pale image shown here. Which of the following explains why the cells are hard to see?