Micro Lab Midterm

What does BSL stand for, and what does an increase from BSL-1 to BSL-4 indicate?

Biosafety level; increasing biological risk and stricter containment

How does an immunocompetent person differ from an immunocompromised person?

An immunocompetent person has normally functioning immune defenses; an immunocompromised person has weakened immune defenses

What does acquiring an infection through inhalation of aerosols mean?

Becoming infected by breathing in tiny airborne particles containing infectious material

In biosafety terminology, how do indigenous and exotic microbes differ?

Indigenous microbes are native to a region

exotic microbes originate elsewhere or are unusual in that region

Which biosafety level involves minimal hazard to laboratory personnel and the environment, with microbes not known to consistently cause disease in immunocompetent adults?

BSL-1

Which biosafety level involves microbes that pose a moderate potential hazard to laboratory personnel and the environment?

BSL-2

Which biosafety level involves indigenous or exotic microbes that may cause serious or potentially lethal disease through inhalation?

BSL-3

Which biosafety level provides maximum containment for dangerous agents posing a high risk of life-threatening infection?

BSL-4

Which organisms are examples of BSL-1 microbes?

Low-risk strains of skin bacteria and yeast

Which microbes are examples of BSL-2 agents?

Herpes simplex virus

common cold viruses such as RSV

rhinoviruses

Salmonella

Which agents are examples of BSL-3 microbes?

Tuberculosis-causing bacteria

SARS-CoV-2

highly pathogenic avian influenza

Yersinia pestis

Which bacterium causes plague?

Yersinia pestis

Which viruses are examples of BSL-4 agents?

Ebola virus

smallpox virus

Why might an immunocompromised person become ill from a BSL-1 microbe?

Weakened immune defenses may fail to control a microbe that normally poses minimal risk to healthy adults

What is the function of a microscope’s body tube?

Maintains optical alignment and provides the light path toward the eyepieces

AKA the microscopes “Head”

What is the function of the prism in a binocular microscope?

Redirects light toward the eyepieces (prism is inside the body tube)

How do a microscope’s prism and body tube differ in function?

• Prism: Redirects light toward the eyepieces

• Body tube: Keeps the lenses aligned and provides a pathway for light

What does the revolving nosepiece do, and how should it be handled?

Holds the objective lenses and rotates to select another objective

(rotate it gently)

How do a microscope’s stage and slide clips differ?

-The stage supports the slide

-The clips secure it

What do a microscope’s mechanical stage controls adjust?

The slide’s horizontal position along the X and Y axes

(left/right & forward/back across the stage)

How do a microscope’s coarse and fine adjustment knobs differ?

Coarse: large, rough adjustments

Fine: small, precise adjustments

Both move the stage vertically

What do a microscope’s arm and base support?

Arm: upper components

Base: the entire microscope

How should a microscope be carried?

One hand gripping the arm

The other supporting the base

What are the functions of a microscope’s lamp and power switch?

Lamp: supplies light

Switch: turns the light on or off

What does the illumination lens near a microscope’s lamp do?

Directs lamp light toward the condenser

What does a microscope’s condenser do?

Focuses light onto the specimen

What does a microscope’s iris diaphragm do?

Controls the amount of light entering the condenser, affecting the image’s brightness and contrast

What is the main light path through a compound microscope?

Lamp → condenser → specimen → objective → ocular → eye

How is the scanning objective identified, color, what is it used for, and FOV?

4×

-Red band

-Used for finding and initially focusing the specimen

-Widest field of view

How is the low-power objective identified, color, what is it used for, and the FOV?

10×

Yellow band

General viewing of smaller structures

Large field of view

How is the high-power objective identified, color, what is it used for, and FOV?

40×

Blue band

Viewing cells and visible organelles in detail

Small field of view

How is the oil-immersion objective identified, color, what is it used for, and FOV?

100×

White band

Viewing bacteria and fine cellular detail

Smallest field of view

How is a microscope’s total magnification calculated?

Ocular magnification × objective magnification

With a 10× ocular, what total magnifications result from 4×, 10×, 40×, and 100× objectives?

4× = 40×

10× = 100×

40× = 400×

100× = 1,000×

How does increasing objective magnification affect field of view and illumination needs?

Smaller visible area; generally needs more light

How does magnification differ from resolution?

Magnification enlarges the image

Resolution separates closely spaced details

Where is immersion oil placed when using a 100× oil objective, and why?

Between the slide and objective

-Reduces light bending and improves resolution

How should a microscope be left after use?

Remove immersion oil as directed;

select 4×

turn off the light

What functions can a bacterial capsule serve?

• Protection and defense

• Attachment to surfaces or other organisms

• Nutrient reserve

What are the main functions of a bacterial cell wall?

• Maintains the cell’s shape

• Provides protection

What does a bacterial plasma membrane do?

Controls which substances enter and leave the cell

What is the bacterial cytoplasm, and what occurs there?

• The cell’s gel-like interior

• Cell growth

• Metabolism—chemical reactions

• DNA replication—copying DNA

What is the bacterial nucleoid?

The region containing the main chromosomal DNA

What is a bacterial plasmid?

• A small, circular DNA molecule

• Separate from the main chromosome

• Carries additional genetic information

What do bacterial ribosomes do?

Make proteins by translating genetic instructions

What is a bacterial pilus, and what does it do?

• A thin, hair-like surface projection

• Helps attach the bacterium to surfaces or other bacteria

How does a bacterial flagellum produce movement?

Rotates like a propeller to move the bacterium

What are the plural forms of pilus and flagellum?

• Pilus → pili

• Flagellum → flagella

What was historically described as a bacterial mesosome?

An infolding of the plasma membrane

How do cocci and bacilli differ in shape?

• Cocci: spherical

• Bacilli: rod-shaped

What is a single, separate spherical bacterial cell called?

Monococcus

What arrangement consists of spherical bacterial cells in pairs?

Diplococci

What arrangement consists of spherical bacterial cells in chains?

Streptococci

What arrangement consists of four spherical bacterial cells in a square?

Tetrad

What are the three layers surrounding the bacterial cell, ordered from outermost to innermost?

• Capsule

• Cell wall

• Plasma membrane

What arrangement consists of spherical bacterial cells in cube-shaped packets, typically eight?

Sarcina

What arrangement consists of spherical bacterial cells in grape-like clusters?

Staphylococci

What is a single rod-shaped bacterial cell called?

Bacillus

What arrangement consists of rod-shaped bacterial cells in pairs?

Diplobacilli

What arrangement consists of rod-shaped bacterial cells in chains?

Streptobacilli

Why does having DNA alone not ensure that a bacterium can make proteins?

• DNA supplies the instructions

• Ribosomes must translate those instructions into proteins

Shines light upward through the slide (microscope)

light source or illuminator

what is located at the base of the microscope?

Contains the on/off switch and power cord

How do “bacillus” and “Escherichia” differ in meaning?

-Bacillus describes a rod-shaped bacterial cell
-Escherichia is a group of bacteria, including E. coli, whose cells are rod-shaped

Adjusts the size of the light beam reaching the slide, helps control image brightness and contrast (microscope)

diaphragm

Switches objective lenses to change magnification (microscope)

nosepiece

what magnification does the eyepiece have on a microscope?

Magnifies the image 10×

Keeps the optics aligned, provides the light path toward the eyepiece (microscope)

body tube

Which focusing knobs can be used with each of the four standard microscope objectives?

• 4× Coarse and fine

• 10× Coarse and fine

• 40× Fine only

• 100× Fine only

Which bacterial cell structure forms an outer protective layer, helps with attachment, and can serve as a nutrient reserve?

Capsule

Which bacterial cell structure maintains the cell’s shape and provides protection?

Cell wall

Which bacterial cell structure controls what enters and leaves the cell?

Plasma membrane

Which part of a bacterial cell is the gel-like interior where growth, metabolism, and DNA replication occur?

Cytoplasm

Which region of a bacterial cell contains the main chromosomal DNA?

Nucleoid

Which bacterial cell component is a small, circular DNA molecule separate from the main chromosome?

Plasmid

Which bacterial cell structures make proteins by translating genetic instructions?

Ribosomes

Which bacterial cell structure is a thin, hair-like projection that helps the cell attach to surfaces or other bacteria?

Pilus

Which bacterial cell structure rotates like a propeller to produce movement?

Flagellum

What term historically described an infolding of the bacterial plasma membrane that is now recognized as a preparation artifact?

Mesosome

What is the purpose of the hanging drop method?

• Observe living, unstained microorganisms in liquid culture

• Distinguish true motility from Brownian motion

How are the coverslip, culture drop, and depression slide positioned in a completed hanging drop preparation?

• Coverslip on top

• Culture drop is hanging under the coverslip

• Slide’s depression is beneath the drop, providing space for free movement

What three functions does petroleum jelly serve in a hanging drop preparation?

• Holds the coverslip in place

• Forms a seal that reduces drying

• Helps maintain a moist chamber that supports living microorganisms

Which objectives are used to locate and examine bacteria in a hanging drop preparation?

• 10× is used to locate the edge of the liquid drop

• 40× is used to examine bacterial cells just inside the drop’s edge

What is true bacterial motility?

Self-propelled movement from one location to another

What is Brownian motion, and what causes it?

• Random jiggling of suspended cells or particles

• Caused by collisions with smaller, fast-moving surrounding molecules

In which states of matter can Brownian motion occur?

• Liquids

• Gases

What do pole and tuft mean when describing bacterial flagella?

• Pole: An end of the bacterial cell

• Tuft: A group of flagella clustered together

Which bacterial flagellar arrangement consists of one flagellum at one end of the cell?

Monotrichous

Which bacterial flagellar arrangement has flagella at both ends of the cell?

• Amphitrichous

• May be shown with a single flagellum or a tuft at each end

Which bacterial flagellar arrangement consists of a tuft of flagella at one end of the cell?

Lophotrichous

Which bacterial flagellar arrangement has flagella distributed around the cell’s surface?

Peritrichous

A bacterium jiggles around roughly the same spot in a hanging drop. Is this sufficient evidence of true motility? Why?

• No

• Molecular collisions can produce Brownian motion without the bacterium propelling itself

A bacterium actively swims from one location to another in a hanging drop. What does this indicate?

True motility

What does the hanging drop method help determine about a microorganism?

Whether it shows true motility

Which two types of movement does the hanging drop method help distinguish?

True motility and Brownian motion

What is the staining status of microorganisms in a hanging drop preparation?

Unstained

Why must microorganisms remain alive when using the hanging drop method to assess motility?

True motility requires the organism to move under its own power

What holds the culture drop in a completed hanging drop preparation?

The underside of the coverslip

What type of microscope slide is used for a hanging drop preparation?

A depression slide, also called a cavity or well slide

What is the purpose of the hollow in a depression slide?

Provides space for the drop to hang and the microorganisms to move freely