MicroBio Quiz 2 Cedarville University Prof Collins

Organisms grown only in the presence of oxygen

Obligate aerobes

Organisms grown in the presence and absence of oxygen

Facultative anaerobes

Organisms that cannot grow in the presence of oxygen

Obligate anaerobes

What is an anaerobic chamber?

Gas pack systems that are used to create anaerobic conditions in a growth chamber. Hydrogen and CO2 are created. O2 is prevented from entering the chamber which creates pressure on the chamber walls.

What does the hydrogen do in the anaerobic chamber?

binds with oxygen and makes water

What does CO2 do in the anaerobic chamber?

creates a positive pressure on the chamber walls, and prevents O2 from entering the chamber.

What is a psychrophile?

an organism who is cold-loving, the optimum growth is 0-15 degrees C

What is a psychrotolerant organism?

an organism that can grow in really cold temps of 0-15 degrees C but grow best in 24-45 degrees C

What is a mesophile?

organism that grows best at moderate temperatures between 25-45 degrees C

What is a thermophile?

an organism who is high heat loving, the optimum growth is above 55 degrees C

What type of organism are most pathogenic organisms?

mesophiles

Define cycrotolerant

Organisms that are capable of growth close to 0°C but with an optimum growth temperature of >20°C

How are microorganisms separated from their environment?

by a selectively permeable plasma membrane

What happens if a bacterium is placed in a hypotonic solution?

water will enter the cell and cause it to become rigid because of the cell wall

What happens if a bacterium is placed in a hypertonic solution?

water leaves and the plasma membrane shrinks away from the wall

Define Plasmolysis

the process in which cells lose water in a hypertonic solution and shrink

What is a halotolerant bacteria?

a bacterium that can tolerate high salt concentrations

What is a halophile?

an organism that grows best in environments with high salt

What is a non-halophile?

an organism that cannot grow in environments with high salt

What is an antiseptic?

A substance that inhibits the growth of bacteria and is commonly applied to the skin

What is a disinfectant?

substances used to kill microbes on inanimate objects

What is an antibiotic?

chemicals that are produced by the biochemical activity of a living organism that kills other living organisms

What is selective toxicity?

A drug that kills harmful microbes without damaging the host

True of False: good antibiotics display selective toxicity

true

What is the Kirby- Bauer method?

Antibiotics are impregnated onto paper disks and then placed on an agar plate using a mechanical dispenser or sterile forceps. After incubation the zone of inhibition is measured.

What is the zone of inhibition?

The area around the antibiotic disk in which bacteria cannot grow

What does a small zone of inhibition mean?

the bacteria is resistant to that antibiotic

What does a large zone of inhibition mean?

the larger the zone the more susceptible that bacterium is to the chemical.

What is the most important step in the Kirby-Bauer method?

removing excess liquid from the sterile disk

What is mode of action?

how an antibiotic attacks

What does penicillin do?

inhibits cell wall synthesis

What does Polymyxin B do?

disrupts cell membrane function

What does chloramphenicol do?

inhibits protein synthesis

What does Erythromycin do?

inhibits protein synthesis

What is selective media?

favor the growth of one organism over another

What are organisms selected for?

using dyes, bile salts, and nutritional sources

What is differential media?

distinguishes between different types of bacteria

What is an EMB plate?

Eosin Methylene Blue

How is an EMB plate selective?

dyes limit growth of gram positive, selects for gram negative

How is an EMB plate differential?

detection between lactose and non lactose fermenting bacteria

What happens if an EMB plate is lactose positive?

black or dark center colonies or green metallic colonies

What happens if an EMB plate is lactose negative?

clear to white colonies

What is a MSA plate?

Mannitol Salt Agar

How is an MSA plate selective?

selects for halotolerant bacteria due to high salt concentrations

How is the MSA plate differential?

contains mannitol and phenol red as a pH indicator

What happens if a MSA plate is a mannitol fermenter?

mannitol is reduced, pH drops and plate turnes YELLOW

What happens if a MSA plate is a non-mannitol fermenter?

mannitol is not reduced, no pH change, plate stays red

Can a blood agar plate be selective?

No

How is a blood agar plate differential?

differentiates between hemolytic and non-hemolytic bacteria

What are hemolysins?

enzymes that destroy red blood cells

What is alpha hemolysis?

partial hemolysis which causes a greening of the agar. Cells are left in tact, but hemin is chemically altered

What is beta hemolysis?

complete lysis of red blood cells resulting in a clear zone of agar

What is gamma hemolysis?

No hemolysis or discoloration of the agar