Microbiology Quiz 2 Flashcards
Organisms growing only in the presence of O2 are called
obligate aerobes
organisms that are able to grow in the presence and absence of O2 are called
facultative anaerobes
organisms that stricly only grown anaerobically and are actually harmed by the presence of O2 are called
obligate anaerobes
which bacteria is a facultative anaerobe?
E. coli
which bacteria is an obligate aerobe?
a. faecalis
which bacteria is an obligate anaerobe?
C. sporogenes
____________ are often used to create anaerobic conditions in a growth chamber. In the gas pack system. hydrogen and CO2 are produced. The palladium catalyst in the growth chamber catalyzes the formation of water from hydrogen and oxygen while CO2 prevents O2 from entering the chamber by creating pressure on the chamber wall
gas pack systems
microorganisms that grown at tempreatures ranging from 015 degrees celsius are known as
psychrophiles
organisms that can grow in cold temperatures, but grow optimally at temperatures between 25-45 degrees celsisus are called
psychotolerant
organisms growing at temperatures between 25-45 degrees celsius are known as
mesophiles
organisms that grow at temperatures above 55 degrees celisus are called
thermophiles
which type of bacteria is a mesophile
S. aureus
Which type of bacteia is a psychotolerant?
P. Plfuorescens
Which type of bacteria is a thermophile?
Bacillus stearothermophilus
bacteria that are able to tolerate high salt concentrations are called
halotolerant
bacteria that thrive in high salt concentrations are known as
halophiles
bacteria that are unable to handle high salt concentrations are
non-halophiles
which bacteria is a non-halophile?
E. coli
Which bacteria is a halotolerant?
S. aureus
What makes EMB selective?
dyes limit growth of gram positive, selects for gram negative
What makes EMB differential?
detection between lactose/non-lactose fermenting bacteria
what makes MSA selective?
selects for halotolerant bacteria such as staphylococcus due to high salt concentrations
what makes MSA differential?
contains mannitol and phenol red as a pH indicator
what does lactose positive look like on an EMB palte?
black or dark center colonies or green metallic colonies
what does lactose negative look like on an EMB plate?
clear to white colonies
what does mannitol fermenter look like on a MSA plate?
Mannitol is reduced, pH drops and plate turns yellow
what does non-mannitol fermenter looks like on a MSA plate?
mannitol is not reduced, no pH change, plate stays red
which bacteria’s colony description is lactose?
E. coli and the plate is green metallic
which bacteria’s colony description is non-lactose?
P. aeruginose and the plate is pink
Which bacteria’s color of agar is mannitol ferment?
S. aureus and the plate is yellow
which bacteria’s color of agar is non-mannitol ferment?
S. epidermidis and the plate is pink
how is blood agar differential?
differentiates between hemolytic and non-hemolytic behavior
what is hemolysins?
enzymes produced that destroy red blood cells
what is partial hemolysis that causes a greening of the agar. The cells are left intact but the hemin is chemically altered
alpha hemolysis
what is complete hemolysis that is caused by the obliteraion of the red blood cells. It produces a clear zone of agar and you can completely see through the palte?
Beta hemolysis
what is no hemolysis, no effect on red blood cells?
gamma hemolysis
which organism has beta hemolysis?
S. aureus and it’s agar description is complete
Which organism has alpha hemolysis?
A. faecalis and it’s agar description is green
Which organism has gamma hemolysis?
S. faecium and it’s agar description is no color
How is blood agar differential?
Differentiates between hemolytic and non-hemolytic behavior
What is hemolysins?
Enzymes produced that destroy red blood cells
What is partial hemolysis that causes a greening of the agar. The cells are left intact but the hemin is chemically altered.
Alpha hemolysis
What is complete hemolysis that is caused by the obliteration of the red blood cells. It produces a clear zone of agar and you can completely see through the plate?
Beta hemolysis
What is no hemolysis, no effect on red blood cells.
Gamma hemolysis
Which organism has beta hemolysis?
S, aureus and it’s agar description is complete
Which organism has alpha hemolysis?
A. faecalis and it’s agar description is green
Which organism has gamma hemolysis?
S. faecium and it’s agar description is no color.
Substances that are commonly applied to the skin are called
antiseptics
Substances usually employed to kill microbes on inanimate objects are called
disinfectants
Chemicals that are produced by the biochemical activity of a living organism that kills other living organisms are called
antibiotics
How are antibiotic sensitivity determined?
Kirby-Bauer Method
What is the Kirby-Bauer method?
Antibiotics are impregnated on thin paper disks. Disks are delivered by a mechanical dispenser or using sterile forceps. After incubation, the ‘zone of inhibition’ is measured. A small zone or no zone indicates that the organism is resistant to the antibiotic. A large zone indicates that the organism is susceptible to the antibiotic.
What does the term selective toxicity mean?
‘Good antibiotics’ display selective toxicity and are limited in the type of organisms that they kill than are antiseptics and disinfectants.
How do antibiotics attack the bacterial cell?
They kill other living organisms.
Which type of media favors the growth of a particular organism while inhibiting the growth of other organisms?
Selective Media
What type of media distinguishes between different types of bacteria?
Differential Media
If bacterium is placed in a ________ solution, water will enter the cell and cause it to become rigid due to the cell wall?
Hypotonic
When bacteria are placed in a _______ solution, water leaves and the plasma membrane shrinks away from the wall?
Hypertonic
What is process called of the plasma membrane shrinking away from the wall?
plasmolysis
