MIcrobio Lab Exam 1

Which of the following biosafety levels contain organisms that pose the greatest risk to your health (ex: Ebola virus).

BSL 4

What is the name of microscope part 3 in the image below?

Objective lens

What is the name of microscope part 5 in the image above?

Coarse adjustment knob

Hand washing removes both transient and normal flora from the surface of the skin.

False

Which picture below shows yeast as seen through a microscope? Circle the correct image.

400x

Which objective do you need to use to properly view bacteria?

100x

Which picture below shows bacilli as seen through a microscope? Circle the correct image.

1000x

When using aseptic technique, you want to place test tube lids onto the lab bench while you are removing or adding bacteria to the test tube.

False

What are two ways you can control the amount of light passing through your specimen when viewing a slide with a microscope?

Adjust the iris diaphragm and the light intensity knob

Growth media

Bacteria food source that is sterile

Incubate

After adding bacteria to media, this is the act of placing that media in a certain temperature/environment to allow bacteria to grow

Culture

Pre-grown bacteria for you to use during lab

Inoculate

The act of intentionally adding bacteria to sterile media

During the last class you placed an inoculated petri plate into a plastic jar. Which plate did you place into this jar?

Anaerobic plate

Which of the following gasses do we use to create an anaerobic environment for the

growth of anaerobic microbes?

Hydrogen (H)

Human pathogens are categorized as __________.

mesophiles

The standard plate count procedure (SPC) uses the lawn plate technique to create the petri plates

False

Based on the name, which growth temperature category do you think Bacillus

stearothermophilusbelongs to?

Thermophiles

What is the purpose of the standard plate count (SPC) procedure?

Determine the number of live cells in a microbial population

Bacteria that cause the milk in your fridge to spoil would be categorized as __________.

Psychotrophs

Turbidity is a sign of…

Bacteria growth

when focusing a microscope on bacteria, which of the following objectives do you need to use during this process?

All four objectives

how do you fast release/blowout the sample from a stereological pipe using a pipe pump

Depress the white button on the side to dispense

which of the following can you confidently say is a pure culture?

A colony on a streak plate

From which of the following situations would you need pure bacterial cultures?

To study bacterial characteristics

when performing technique how many times should you pull your sterilized loop through streak one when making streak two and three streak two making streak three

Two

how do you make a pour plate?

Add bacteria to an empty sterile plate pour liquid of agar into plate swirl

why do we use stains to view bacteria?

Bacterial cells are basically transparent, so we need stains to see them

the simple stain technique uses a basic die, which will stain the cells and leave the background of the slide unstained

true

Which technique below did you use to determine if the organisms in your sample are motile

Wet mount

uses a stain that is negatively charged (acidic) like nigrosin

Negative stain

uses no stain organisms were suspended in water

Wet mouth

uses a stain that is positively charged (basic) like methylene blue

Simple stain

require requires the slide to be heat fixed before staining

Simple stain

why do we heat fix slides before performing certain stains?

To dehydrate bacterial cells and attach them to the slide

which choice below describes the type of stains you used in the capsule stain

Two stains: one died the background one died the cell

what color is the capsule following the capsule stain?

Clear

the Graham stain needs to be heat fixed before stating

true

The thickness of the peptidoglycan layer is thick. Is it gram-positive or gram-negative?

Gram-positive

Gram-negative bacteria is pink

True

Suppose you perform a Graham stain on a slide that contains only a gram-positive organism when you look at the slide with the microscope, you noticed that half of the cells are purple half or pink what is the most likely cause of this?

Added too much 95% ethanol or over decolorization

which of the following organisms did you use to perform the cell viability stain the method we used to involve the stain methylene blue

SACCHAROMYCES CEREVISIAE (yeast)

decolorizing agent used in the Gram stain

95% ethanol

secondary stain used in the Graham stain

Safranin

primary stain used in the Gram stain

Crystal Violet

substance that fixes the primary stain into the cell wall in the Gram stain (mordant)

Grams iodine

Psychrophiles

Found in the ocean, Arctic and Antarctic habitats

psychotrophs

Include some food spoilage organisms

mesophiles

Numerous human pathogens

thermophiles

Composting material and Hot Springs

extreme thermophiles

Hot ocean floor riches

strepto

chain

staphyl

clusters

Disinfectant

Used on inanimate surfaces

antiseptic

Used on living tissues

Examples of disinfectant are

Lysol and bleach

Examples of antiseptic are

Hydrogen peroxide and isopropyl alcohol

What is the purpose of the Kirby Bauer method?

To determine if an antibiotic is effective against a bacterium of interest

As seen below, E. coli grew in both aerobic and anaerobic conditions. Based on these results,
how would you classify E. coli based on aerotolerance?

Facultative anaerobe

If your 10-5 plate from the SPC procedure has 107 colonies, approximately how many
colonies would you expect to see on your 10-6 plate?

~11

You count 483 colonies on your 10-4 plate. What is your next step?

Invalid plate – too many colonies so you need to count the 10-5 plate

What do antiseptics do?

Decrease the amount of bacteria on skin

When preparing an antiseptic, you want to make sure it is as strong as possible to make sure it will work.

False

Based on the table below, how would you categorize Ps. fluorescens in terms of its growth temperature requirements?

psychotrophs

Number the steps of the flamed forceps technique in order. There may be some steps in the list that are not part of the procedure.

Did forceps in ethanol

Quickly pass forceps through the flame

Hold forceps in the flame until they turn orange/red

Use newly sterilized forceps

re-Sterilize forcepss after each use

UV light is an excellent choice to use as a non-chemical based antiseptic because it will kill all the bacteria on the skin.

false

When testing the effectiveness of different antiseptics and disinfectants against E. coli,
you notice that there is a large zone of inhibition surrounding the bleach and isopropyl
alcohol discs and no zone surrounding the Lysol or hydrogen peroxide discs. Based on
this information, which antiseptic should you use against E. coli?

Isopropyl alcohol

The plates below were exposed to UV light for 120 seconds. As you can see, there is still significant growth on the B. megaterium plate while the S. marcescens has been killed. Why do you think B. megaterium was able to survive?

B. megaterium makes endospores

While testing the effectiveness of ampicillin against S. epidermidis, you measured the zone of inhibition and found it was 18 millimeters (mm) in diameter. Based on the information provided in the Kirby-Bauer chart shown below, this strain of S. epidermidis is ___________________ ampicillin.

R (Resistant) I (Intermediate) S (Susceptible)
E. coli < 11mm 12-13mm > 14mm
S. epidermidis < 28mm > 29mm

Resistant to