EXAM 2 MCB3020 BACUSMO

The process of forming a cross wall between two daughter cells during the bacterial cell cycle is called

CYTOKINESIS

The collective process of the cytoplasm being divided into the daughter cells is called

cytokinesis

Bacteria and archaea mainly reproduce by

binary fission

One role of the cell wall in bacteria is to protect cells from bursting due to excessive

turgor pressure

The complete sequence of events extending from formation of a new cell through the next division is called the_____ cycle.

cell

Broth cultures that are grown without the addition of fresh media are called____ cultures.

batch

In general, which of the following organisms tends to have a single circular chromosome composed of DNA?

bacteria

Which process forms cross walls between daughter cells during cytokinesis?

septation

The component of the bacterial cell envelope that protects the cell from swelling and bursting from turgor pressure is

peptidoglycan

The length of time that it takes a culture to double in cell number is called the _______ time.

generation

Microorganisms that can grow under very harsh conditions are called

extremophiles

In a hypotonic solution, cells will often Blank______ if they are unable to counter the effects of osmosis.

burst

One role of the cell wall in bacteria is to protect cells from bursting due to excessive Blank______

turgor pressure

Cells are likely to shrivel when placed in a _______ solution, in the absence of a response to osmosis

hypertonic

If the environment has a higher solute concentration than the interior of the cell, the environment is Blank______.

hypertonic

Consider a culture that has a generation time of 15 minutes. After 1 hour of growth in exponential phase there will be Blank______ generations.

4

Which type of microbe is most likely to be cultured from the Great Salt Lake?

Halophiles

The negative logarithm of the hydrogen ion concentration of a solution is its Blank______.

pH

Which growth temperature iS considered one of the three cardinal temperatures?

MINIMUM, MAXIMUM, OPTIMUM

An organism's optimal growth temperature is closest to its Blank______.

maximum growth temperature

Microbes that grow best at temperatures of 15°C are called

psychrophiles (cryophiles)

Microbes that grow best at 37°C are called

mesophiles

Microaerophiles and aerotolerant anaerobes are different because Blank______.

microaerophiles require oxygen but aerotolerant anaerobes do not

Microbes that can grow at high physical pressures are considered to be

piezophilic (barophilic)

True or false: Maximum growth temperature for an organism is invariable, a strict characteristic of each organism, determined by the properties of its molecular components.

False

The type of electromagnetic radiation most harmful to cells is Blank______.

Multiple choice question.

ultraviolet

visible

ionizing

infrared

ionizing

Microorganisms that grow well in refrigerated food are best described as Blank______.

psychrophiles

Habitats that are low in nutrients are called_________ environments.

oligotrophic

A microorganisms whose generation time is shortest at 37°C is called a(n) Blank______.

mesophile

Match each term describing a type of oxygen tolerance with its definition.

Instructions

1. obligate aerobe

2. microaerophile

3. facultative anaerobe

4. aerotolerant anaerobe

5. obligate anaerobe

1. completely dependent on atmospheric oxygen

2. require oxygen at levels below atmospheric oxygen

3. grows with or without oxygen, but grows faster with oxygen

4. tolerates oxygen in its environment but does not use it

5. killed by prolonged exposure to oxygen

The two interchangeable terms that describe an organism that requires high pressure of more than 1 atm for growth are ______ and ______.

barophilic / piezophilic

Microbes that naturally live attached to surfaces in aquatic environments are Blank______.

sessile

Using molecular signals to communicate microbial density is referred to as ___________ sensing

quorum

Environments that are high in nutrients are Blank______.

eutrophic

Which two of the following are effective ways to inhibit the growth of microorganisms?

Multiple select question.

- Stimulating reproduction by binary fission

- Increasing the level of nutrients in the

- growth medium

- Starvation

- Poisoning

starvation

poisoning

Which of the following best defines biocides?

Multiple choice question.

A. A biocide kills microbes.

B. The term biocide describes all antimicrobials that can be used to control microbes.

C. The term biocide refers only to chemical treatments that kill microbes.

D. A biocide inhibits the growth of microbes but does not kill them.

B. The term biocide describes all antimicrobials that can be used to control microbes.

Microbes that naturally live free-floating in aquatic environments are ______.

PLANKTONIC

When an object is totally free of viable microorganisms, spores, viruses, prions, and other infectious agents, it is said to be _______.

STERILE

The exchange of signaling molecules to coordinate gene expression between members of a bacterial population is called Blank______.

Multiple choice question.

A. quorum sensing

B. binary fission

C. biofilm formation

D. transcription

Quorum Sensing

Which of the following terms describes a chemical that is used destroy all infectious agents (including viruses and endospores) on an object?

sterilant

Which of the following microbial systems are most commonly exploited to control the growth of microorganisms?

Multiple choice question.

Photosynthesis

Membrane biogenesis

Microbial nutrition

Genetic exchange

microbial nutrition

Disinfection is the removal of Blank______ from an object.

microorganisms that may cause disease

The terminology used to describe different microbial control agents is important to understand because Blank______.

- some treatments have different effects depending on the conditions

- some of the words are in common use with imprecise meanings

The process of controlling microbial growth on living tissue is called

antisepsis

Choose two phrases that describe "disinfection".

Multiple select question.

The destruction of potential pathogens

The elimination of all microbes

The conversion of viable cells to persisters

The reduction of the microbial population

-The destruction of potential pathogens

-The reduction of the microbial population

The D value of a biocidal agent is measured in units of

time

On which two objects would you use a disinfectant to control microbial growth?

-diaper changing table

- bathroom sink

FIltration is an effective means of sterilization for liquid solutions. Its effect on microorganisms is to Blank______.

Multiple choice question.

remove them from the solution

Which two of the following describe a depth filter?

Multiple select question.

- Thin layer of material with straight channels

- Thick layers tightly bound together with no channels

- Thick layer of fibrous or granular materials

- Contains narrow, twisting channels

- Thick layer of fibrous or granular materials

- Contains narrow, twisting channels

A numerical measure of the efficiency of a biocidal agent is the time required to kill 90% of the culture. This number is the_____ value.

D

True or false: Treatment with moist heat affects nucleic acids, proteins, and cell membranes.

T

Choose three commonly used physical methods for sterilization.

Multiple select question.

Bacteriophage

Phenolics

Heat

Radiation

Filtration

Heat

Radiation

Filtration

Which of the following would not be killed by a treatment of boiling for 10 minutes?

Multiple choice question.

Fungal cells

Bacterial cells

Fungal spores

Bacterial endospores

Bacterial endospores

The device used for steam sterilization in a microbiology lab is the .

autoclave

Filtration is an effective means of sterilization for which two of the following?

Multiple select question.

Gases

Medical instruments

Powdered media

Chemical solutions

-Gases

-Chemical solutions

Standard conditions for sterilization in an autoclave are Blank______.

121°C and 15 pounds of pressure

Which three of the following cellular components are most sensitive to moist heat?

Multiple select question.

Cell wall

Membranes

DNA

Proteins

Peptidoglycan

Cell wall

Membranes

DNA

Color change on autoclave tape indicates that Blank______.

the tape and the contents of the autoclave have been heated

Boiling water is best described as which of the following?

Disinfectant

During pasteurization, milk is treated for a defined time at what temperature?

Heated but not to boiling

What temperature of moist heat will eliminate most bacterial endospores?

Multiple choice question.

Temperatures above 100°C

In the microbiology laboratory, the inoculating loop is sterilized by holding it in the flame of a burner until it glows red hot. This is an example of sterilization by Blank______.

oxidation

UV light at a wavelength of Blank______ nm is lethal, due to the formation of thymine-thymine dimers in DNA.

Multiple choice question.

260 nm

Standard autoclave conditions (121°C, 15 pounds of pressure, 15 minutes) will sterilize which two of the following?

Multiple select question.

-250 ml empty Pyrex flasks

-3 ml bacterial broth culture in a test tube

Verification of the success of an autoclave run is measured by Blank______.

including bacterial endospores in the run and testing their viability following the run

Which of the following statements regarding chemical disinfectants is correct?

Multiple choice question.

- A good disinfectant should have a distinctive odor to monitor its use.

- A good disinfectant will tingle on the skin as it works.

- A good disinfectant must be hydrophobic to penetrate membranes.

- A good disinfectant will be effective against a variety of infectious agents.

- A good disinfectant will scrub the finish off of delicate surfaces.

- A good disinfectant will be effective against a variety of infectious agents.

What time frame is appropriate for heating objects in an oven at 160° to 170°C for sterilization?

2-3 hours

UV radiation around 260 nm causes thymine-thymine dimerization of DNA which prevents which two of the following processes?

Multiple select question.

Transcription of RNA

DNA replication

The first widely used antiseptic and disinfectant was Blank______.

phenol

The primary mechanisms of action of alcohols on bacterial cells are to Blank______.

Multiple select question.

oxidize proteins

denature nucleic acids

denature proteins

dissolve membrane lipids

denature proteins

dissolve membrane lipids

Which three properties are important for a good, general purpose, chemical disinfectant?

Multiple select question.

Effective against a range of microorganisms

Contains viricidal properties

A strong recognizable odor

Acidic pH

Non-toxic to humans or animals

-Effective against a range of microorganisms

-Contains viricidal properties

-Non-toxic to humans or animals

Which one of the following halogens is used as an antiseptic?

Multiple choice question.

Astatine

Fluorine

Iodine

Bromine

iodine

What is the mechanism of action of heavy metals on bacterial cells?

Multiple choice question.

-Solubilize the plasma membrane

-Complex with sulfhydryls on proteins to inactivate them

-Disrupt ion gradients across the cell membrane

-Denature the chromosomal DNA

-Complex with sulfhydryls on proteins to inactivate them

The primary mechanisms of action of quaternary ammonium compounds are Blank______.

Multiple select question.

denaturation of nucleic acids

disruption of microbial membranes

denaturation of proteins

oxidation of protein sulfhydryls

-disruption of microbial membranes

-denaturation of proteins

Phenol was promoted to reduce the risk of infection during surgery by Blank______.

Multiple choice question.

Joseph Lister

Which two of the following terms describe the effects of sterilizing gases on microbial cells?

Multiple select question.

Microbicidal

Fungistatic

Sporicidal

Microbistatic

-Microbicidal

-Sporicidal

What is the primary mechanism of action of halogens against microbial cells?

Multiple choice question.

Solubilizes cell membranes

Denatures proteins

Denatures nucleic acids

Oxidizes cell constituents

Oxidizes cell constituents

Which heavy metal is an effective algicide?

copper

An organic antimicrobial agent with an amphipathic structure, having both polar and nonpolar components, is termed a(n) Blank______.

Multiple choice question.

antibiotic

detergent

disinfectant

antiseptic

detergent

On the left side of the figure, which component of a Gram negative cell is affected by glutaraldehyde?

Proteins in the outer membrane

What are the primary mechanisms of action of ethylene oxide gas as a sterilizing agent?

Multiple select question.

Alkylates nucleic acids

Alkylates proteins

Oxidizes proteins

Solubilizes membranes

Alkylates nucleic acids

Alkylates proteins

On the right side of the figure, which component of a Gram positive cell is affected by glutaraldehyde?

Peptidoglycan in the cell wall