MicroBio unit 3

Typical conditions used for sterilization are

121°C at 15 psi for 15 minutes.

Aqueous solutions of alcohol at a concentration of ______ are more effective than 100% alcohol.

60-80%

Eukaryotic cells have 80S ribosomes. Prokaryotic cells, however have ___ ribosomes, composed of a 50S and 30S subunit. The structure of these prokaryotic ribosomes is different enough from the eukaryotic ones that they can be selectively targeted by antibacterial drugs.

70S

Which of the following are systems bacteria can use to protect against invading DNA?

CRISPR immunoglobulin formation restriction-modification microarrays polymerase chain reaction

Controlling microbial growth is important in which of the following scenarios?

Caring for an open wound Manufacturing of food products Preparing a patient for surgery Testing a water sample for bacterial contamination Caring for an open wound Manufacturing of food products Preparing a patient for surgery

Which of the following are resistant to destruction by typical disinfection methods?

Clostridium endospores

Compared with antibacterial, antifungal, and antiviral drugs, why does relatively little research and development go into antiprotozoan and antihelminthic drugs?

Most parasitic diseases are concentrated in the poorer areas of the world where people simply cannot afford to spend money on expensive medications.

A patient has a urinary tract infection. Why is this a good example of an infection that can usually be treated well with bacteriostatic antimicrobials, e.g., sulfa drugs?

Once bacterial growth is stopped, urination can usually be counted on to flush the pathogens

To treat a case where the patient's defenses are unlikely to clear an infection, which would be the more appropriate choice of an antimicrobial drug, one that is bactericidal or bacteriostatic?

One that is bactericidal.

Lister developed his ideas on prevention of infection during medical procedures after studying the work of

Pasteur.

Because CRISPR systems involve bacteria using retained segments of DNA to identify and destroy future invading phage DNA, these systems are a form of ______.

adaptive immunity

When antimicrobials are used in combination, and their interaction is neither antagonistic nor synergistic, the combination is said to be ___

additive

A sterile object is free of ______.

all viable microorganisms and viruses

In conjugation the donor cell is recognized by the presence of

an F plasmid.

The antimicrobials produced by some molds and bacteria are generally called

antibiotics.

Chemicals used in the therapy of infectious diseases are called ___ medications.

antimicrobial

Chemotherapeutic agents that are used to treat microbial infections can be more specifically called ___ medications.

antimicrobial

Radio waves, X-rays, microwaves, UV light and gamma rays are all examples of ______.

electromagnetic radiation

The most highly resistant microbial structure is the bacterial ___

endospore

Medications effective against HIV include post-attachment inhibitors, CCR5 antagonists, and fusion inhibitors. These three groups are collectively called ___ inhibitors.

entry

The target of most antifungal drugs is ___, a sterol found in the plasma membrane of fungal but not human cells.

ergosterol

The target of most antifungal drugs is

ergosterol.

Compared with bacteria, there are relatively few drugs available for use against fungal pathogens because ______.

eukaryotic pathogens such as fungi more closely resemble human cells than do bacteria

True or false: Because helminths and protozoa were recognized to cause diseases long before the roles of bacteria and viruses were understood, much more research has gone into understanding these organisms. As a result, we have many more antiprotozoan and antihelminthic drugs available, which is why these diseases tend to get so little coverage.

false

True or false: Choosing which germicide to use is not that complicated since we only consider how effective it is against the target microbes.

false

True or false: In bacterial conjugation, all F+ donor cells are high frequency recombinant (Hfr) cells. True false question.

false

True or false: In bacterial conjugation, all F+ donor cells are high-frequency recombinant (Hfr) cells.

false

True or false: Most antibacterial medications interfere with metabolic pathways.

false

Which four of the following microbial groups are the most resistant to chemical control methods?

nonenveloped viruses Mycobacterium species vegetative bacteria protozoan cysts and oocysts enveloped viruses bacterial endospores nonenveloped viruses Mycobacterium species protozoan cysts and oocysts bacterial endospores

Which type of DNA repair is shown in this figure?

nucleotide excision repair

The first antibiotic, ___, was discovered in 1928 by Alexander Fleming.

penicilin

This figure shows the steps of ______, a process that repairs thymine dimers by breaking the covalent bonds that have formed between adjacent thymines.

photoreactivation

Heat treatment, irradiation and filtration are examples of ______ used to control microorganisms.

physical processes

The act of delaying spoilage is ______.

preservation

High- ___ processing (HPP) is used to decrease the number of microbes in food while maintaining the color and flavor.

pressure

Entry inhibitors are a new group of drugs effective against HIV that ______.

prevent the virus from penetrating the host cells

Antivirals that interfere with viral uncoating ______.

prevent viral replication by preventing the nucleic acid from separating from the protein coat

Repair of nucleotide incorporation errors during the process of DNA replication is accomplished by ___ by DNA polymerase and by ___ repair.

proofreading and mismatch

Medically useful antimicrobial drugs exhibit ___ ___, meaning they cause greater harm to microbes than to the human host.

selective toxicity

Medical instruments are classified into three categories according to their risk for transmitting pathogens. These are: critical instruments, ___ instruments, and ___ instruments.

semicritical; noncritical

The main effect of low temperature storage is to ______.

slow the activity of microbes

Trimethoprim and sulfonamides have a(n)

synergistic effect.

True or false: An antimicrobial medication is a chemical used to treat an infectious disease. True false question.

true

True or false: Compared to conventional methods of antimicrobial susceptibility testing, commercial modifications are less labor-intensive.

true

true or false: Boiling is very effective at removing most common waterborne pathogens.

true

Which organization recently published a document that lists the most serious threats with respect to antibiotic resistance?

CDC

Planar molecules used as chemical mutagens are called

intercalating agents.

Tavaborole is one of the more recently developed antifungal medications. It inhibits protein synthesis by ______.

interfering with an enzyme that "charges" a tRNA molecule by attaching the correct amino acid

One of the most dramatic examples of antimicrobial resistance are the enterococci, a group of bacteria that is part of the normal microbiota of the ______ and a common cause of healthcare-associated infections.

intestine

Liquid media containing heat-sensitive components would best be sterilized by

membrane filtration.

The lowest concentration of a specific antimicrobial drug needed to prevent the growth of a given bacterial strain in vitro is known as the ___ ___ concentration

minimum inhibitory

Household bleach applied at 55C is ________ effective in killing bacteria than if it were applied at 50

more

A(n) ____ is a change in the nucleotide sequence of DNA that is passed on to daughter cells.

mutation

Although antimicrobial resistance can result from the acquisition of new genes, it can also be due to the altering of existing genes via spontaneous ___

mutation

The source of variation among microorganisms that were once identical is

mutation.

During repair of oxidized guanine, which enzyme removes the damaged nucleobase from the sugar-phosphate backbone?

DNA glycosylase

Fluoroquinolones typically target

DNA gyrase.

In humans, two of the genes associated with the development breast cancer encode enzymes involved in ______.

DNA repair

True or false: A point mutation always leads to a shift of the reading frame from the point of mutation downstream.

False

When certain bacteria are said to have intrinsic (innate) resistance, this means they have ______

some inherent property that makes them generally more resistant to the effect of some antimicrobials

Mutations that arise naturally during cellular metabolism, and not as a result of exposure to mutation-causing agents, are called ___ mutations

spontaneous

Following treatment to remove all viable microorganisms, including viruses, an object is considered to be ___

sterile

The process of killing or removing all of the microorganisms in or on a material is called

sterilization.

A common application of dry heat in the microbiology laboratory is to

sterilize the inoculating loop.

Which of the following does not kill microbes but physically removes them?

Filtration

Which of the following antimicrobials inhibit nucleic acid synthesis?

Fluoroquinolones, rifamycins, and metronidazole

One of the earliest antimicrobials isolated from a bacterium was

streptomycin.

Base ______ mutations occur when an incorrect nucleotide is incorporated in place of another during DNA synthesis.

substitution

The most common type of mutation is base ___, where an incorrect nucleotide is incorporated during DNA replication.

substitution

When selecting an appropriate chemical disinfectant, it is important to realize that the death rate is significantly influenced by ______.

temperature pH

Drugs in a family called echinocandins interfere with synthesis of β-1,3 glucan. As a result, ______.

the fungal cell wall will be weakened and the cell will burst

Why is it much more difficult to develop drugs that will effectively control fungal pathogens than it is to control bacterial ones?

Humans and fungi are both eukaryotes, so antifungal drugs are likely to have adverse effects on the human as well.

Antibacterials like daptomycin and polymyxin B essentially make holes in the bacterial membrane. Why, in terms of the function of the membrane, is this deadly to bacteria?

It makes the membranes no longer selectively permeable.

What is a special consideration when giving antimicrobials to patients who have kidney or liver dysfunction?

They may excrete or metabolize drugs more slowly, so their dosages should be adjusted accordingly to avoid toxic levels.

Why is it so difficult to selectively target viruses with drugs?

They rely almost exclusively on the host cell's metabolic machinery for their replication, so there are few targets for selective toxicity.

Why do antimicrobials that target the bacterial cell wall usually have a very high therapeutic index?

They target peptidoglycan synthesis, which is only found in bacteria, not eukaryotic cells, so they have low toxicity.

Antimicrobials that are effective against a wide range of bacteria are known as ___ - ___ antimicrobials.

broad-spectrum

The consequences of not repairing damaged DNA in cells include ______.

cancer (in animals) increased activity of RNA polymerase cell death cells that have fewer mutations

One of the first chemicals used by Lister to prevent surgical infections was

carbolic acid.

Chemicals that cause cancer are known as ______, and most of them are ______. Multiple choice question. mutagens; teratogens

carcinogens; mutagens

Quaternary ammonium compounds are

cationic detergents that help wash surfaces.

Adding sorbic, propionic, and benzoic acid to foods affects ______ of microbes.

cell membrane function

Antimicrobial medications (also referred to as antimicrobial drugs or simply antimicrobials) are best defined as ______.

chemicals that inhibit the growth of or kill microorganisms

Protease inhibitors are used to treat HIV infections by inhibiting the HIV-encoded protease, preventing it from ______.

cleaving the translated polyprotein into individual proteins

The genes that are present in all strains of a given species are called the ______.

core genome

A surgical scalpel is rated as a ______ instrument because it penetrates skin and mucous membranes and therefore must be sterile.

critical

Ultraviolet radiation at the bactericidal wavelength destroys bacteria by

damaging nucleic acid.

What are four common mechanisms of acquired resistance to antimicrobial medications?

increased elimination of the drug production of a drug-inactivating enzyme decreased uptake of the drug alteration in the target molecule ^ alteration of the DNA in response to the drug

An auxotroph can be isolated from a prototrophic parent strain by ______ selection.

indirect

___ selection is used to isolate an auxotroph from a prototrophic parent strain, because no selective medium exists to inhibit the parent.

indirect or negative

Mutations that are caused by external influences such as radiation or chemicals are called ______ mutations.

induced

Drugs that are bacteriostatic

inhibit the growth of bacteria.

Irradiation of cells with ultraviolet light may cause

thymine dimers.

The mechanism by which genes are transferred into bacteria via viruses is called

transduction.

The genetic transfer mechanism shown here is called ___

transformation

Which of the following are the three main methods of gene transfer in bacteria?

transformation transposition conjugation competition translocation transduction

Mutagens that are DNA segments that can insert into genes and thereby inactivate them are called ______.

transposons

Segments of DNA that can move to new positions within the genome of a single cell are called ___

transposons

true or false: The more bacteria one starts with, the longer it will take to kill them all.

true

Germicidal chemicals ______.

usually react irreversibly with proteins, DNA, cytoplasmic membranes, or viral envelopes are often poorly understood with regards to mechanisms of action

Restriction-modification systems were discovered ______.

while studying why certain bacterial strains are relatively resistant to phage infection

Match each characteristic with the appropriate nucleic acid molecule.

contains an origin of replication- both plasmids and chromosomes made of double-stranded RNA- neither plasmids nor chromosomes typically do not encode genes essential to the life of the cell- plasmids only found in all eukaryotes and prokaryotes- chromosomes only

In E. coli, less than 50% of the genes are found in all strains. These conserved genes are called the ___ genome.

core

The antifungal drug griseofulvin interferes with the action of tubulin, the protein that polymerizes to form microtubules and a factor necessary in nuclear division. Tubulin is found in all eukaryotic cells. How can the selective toxicity of griseofulvin be explained?

Greater uptake by fungal cells

Drugs that prevent HIV from inserting the DNA copy of its genome into that of the host cell are called integrase strand transfer inhibitors (INSTIs), or simply ___ inhibitors.

integrase

The figure shows results from the ___ - ___ disc diffusion test for determining the susceptibility of a given bacterial strain to a variety of antimicrobial medications.

Kirby-Bauer

Which test provides qualitative results regarding antibiotic susceptibility and is reported as susceptible, intermediate, or resistant?

Kirby-Bauer test

The Kirby-Bauer disc diffusion test is routinely used to determine ______.

the susceptibility of a given bacterial strain to an assortment of antimicrobial drugs

The toxicity of a given drug is expressed as the

therapeutic index.

A new antifungal medication, tavaborole, inhibits protein synthesis by interfering with an enzyme that "charges" a tRNA molecule by attaching the correct amino acid. It is used ______.

topically to treat nail infections

Which mechanism of gene transfer involves the uptake of "naked" DNA by competent bacterial recipient cells?

transformation

In prokaryotes, genes can be transferred from a donor to a recipient via three different mechanisms: ___, ___, and ___.

transformation, transduction, and conjugation

The drug griseofulvin targets cell division by interfering with the action of ___, the protein that polymerizes to form microtubules and a necessary factor in nuclear division.

tubulin

Errors by DNA polymerase that incorporate the wrong nucleotide into replicating DNA can be repaired quickly by which two mechanisms?

Proofreading by DNA polymerase Mismatch repair Photoactivation Excision repair SOS repair

The process of bacterial ___ involves the uptake of "naked" DNA by competent bacterial recipient cells.

transformation

Random genetic changes that result from normal cellular processes are ______.

spontaneous mutations

The mechanism by which bacterial DNA is moved from one bacterium to another by a bacteriophage is called ___

transduction

Segments of DNA capable of moving from one area in the DNA to another are called

transposons.

True or false: The risk of developing a fatal infection after surgery has substantially decreased since the late 19th century because modern hospitals now have procedures in place to avoid microbial contamination.

true

Many enterococci have R plasmids; some strains, called ___ - ___ ___ (VRE), are even resistant to vancomycin.

vancomycin- resistant enterococci

Match each antibacterial medication with its appropriate mechanism of action.

vancomycin-cell wall (peptidoglycan) synthesis fluoroquinolones-nucleic acid synthesis daptomycin-cell membrane integrity trimethoprim-metabolic pathways (folate biosynthesis) aminoglycosides-protein synthesis

Antiviral drugs that interfere with nucleic acid synthesis target ______.

virally encoded enzymes that replicate viral nucleic acid

Cancer-causing chemicals are called ___

carcinogens

Consider the following classes of antibacterial medications. Match each with its correct target.

β-lactam drugs- matches Choice, cell wall (peptidoglycan) synthesis rifamycins-nucleic acid synthesis polymyxin B-cell membrane integrity sulfonamides-metabolic pathways (folate biosynthesis) tetracyclines-protein synthesis

Integrase inhibitors offer a new option for treating HIV infections by ______.

preventing the virus from inserting the DNA copy of its genome into that of the host cell

Consider the use of low temperature storage for the preservation of food. Which of the following are accurate statements?

-Psychrotrophic and some psychrophilic microorganisms can grow at refrigeration temperatures. -Refrigeration inhibits the growth of many pathogens and spoilage microorganisms by slowing or stopping critical enzyme reactions.

Which of the following statements about transformation is correct?

-Transformation depends on a donor cell containing an F plasmid and a recipient cell that does not. -Transformation is the uptake of naked DNA from the environment. -Transformation involves the formation of a sex pilus through which plasmid DNA is shared between bacteria. -Transformation is the transfer of DNA from one bacterial cell to another by means of a bacteriophage.

Genetic change in bacteria occurs through which two mechanisms?

1. Horizontal gene transfer 2. vertical gene transfer 3. mutation HORIZONTAL GENE TRANSFER and MUTATION

Which of the following types of radiation are mutagenic?

1. Ultraviolet rays 2. X-rays 3. Infrared rays ULTRAVIOLET RAYS and X-RAYS

Which of the following are physical ways to remove or destroy microbes?

Autoclaving Incineration Filtration Ultraviolet radiation

For which of these organisms is there a large increase in antibiotic resistance resulting from a lack of patient compliance with the 6 -12 month course of daily antibiotics?

?? Staphylococcus.

Explain how drug resistance develops in bacteria and ultimately limits the usefulness of all known antimicrobials.

Antimicrobials kill or inhibit sensitive organisms, providing a selective advantage to resistant strains; these strains spread in the population.

Which of the following species are the four major producers of antibiotics?

Aspergillus (fungus) Histoplasma (fungus) Bacillus (bacterium) Cephalosporium (fungus) Mycobacterium (bacterium) Streptococcus (bacterium) Penicillium (fungus) Streptomyces (bacterium)

Chemical mutagens can cause two types of mutations: ___ substitutions and ___ mutations.

Base and frameshift

Antimicrobials differ not only in their action and activity but also in how they are distributed, metabolized, and excreted by the body. Match the following drug properties that need to be considered with the appropriate usage.

Drugs that are unstable at low pH-Administered through intravenous or intramuscular injection Drugs that can cross from the blood into the cerebrospinal fluid-Used to treat meningitis Short half-life-Taken often, typically multiple times each day Long half-life-Taken infrequently, often only once a day or less

One of the earliest researchers to explore the use of chemicals to kill microbial pathogens was

Ehrlich.

When integrated F plasmid DNA in an Hfr cell is excised from the chromosome, an excision error can result in the removal of chromosomal DNA along with the F plasmid DNA, creating a plasmid called ______.

F'

When an excision errors produces a plasmid containing both chromosomal and F plasmid DNA, the resulting plasmid is called a(n) ___ plasmid.

F' or F prime

______ is the destruction of microbes by subjecting them to extremes of dry heat, reducing them to ashes.

Incineration

______ provides an alternative to heat for sterilization and disinfection, but the process damages some types of plastics.

Irradiation

The majority of antifungal drugs target ergosterol. Why is this so?

It is a sterol found in the cytoplasmic membrane of fungal, but not human, cells.

In 1928, Alexander Fleming noticed that colonies of Staphylococcus aureus growing near a contaminating mold looked as if they were dissolving. He identified the mold, which was producing the first discovered antibiotic, as a species of ___

Penicillium

Chemicals called ___ are used to prevent the growth of undesirable organisms in foods and beverages.

Preservatives

Which of the following use moist heat to destroy microbes?

Pressurized steam Pasteurization Boiling

A common environmental organism that may even grow in certain chemical disinfectants is

Pseudomonas aeruginosa.

Extensively damaged DNA activates the ___ repair mechanism, which cannot always determine the correct nucleotide sequence, thus introducing mutations resulting from the repair process itself.

SOS

______ repair is activated by extensive DNA damage and uses a polymerase that lacks proofreading ability, ultimately resulting in mutations.

SOS

______ destroy all microbes, including viruses and endospores.

Sterilants

When treating an infection with a combination of antimicrobials, why might a bacteriostatic drug be antagonistic when used with a bactericidal drug?

The bactericidal drug relies on actively dividing cells to work; the bacteriostatic drug prevents cells from actively dividing.

After testing to determine the susceptibility of an organism to various drugs, what are important considerations when choosing a drug to use?

The drug should act against as few other bacteria as possible. The drug should act against the pathogen. The drug should kill as many species of bacteria as possible. The drug should have a low therapeutic index.

What is one disadvantage of using heat treatment to sterilize plastic items?

The items may melt.

What allows for selective toxicity in a medication?

The medication acts against an essential component or biochemical process of human cells that does not exist in microorganisms.

Considering that all cells synthesize proteins, how is it possible to selectively target prokaryotic protein synthesis with antibacterials?

The structure of the prokaryotic 70S ribosome is sufficiently different from the eukaryotic 80S ribosome.

Compared to conventional methods, commercial modifications of antimicrobial susceptibility testing offer what advantages?

They are more effective at testing for anaerobic microorganisms. The results can be obtained more quickly. They can test for microbes that cannot be tested via the other methods. They are less labor-intensive. The results can be obtained more quickly. They are less labor-intensive.

Effective antimicrobial drugs would need to demonstrate selective toxicity. What does this mean?

They cause greater harm to microbes than to the human host.

There are a few antibacterial medications that interfere with cell membrane integrity. How do they lead to bacterial cell death?

They cause the cells to leak.

Why do fungal cell walls make a good target for some antifungals?

They contain some components not produced by animal cells.

What best explains why the first-line drugs are generally given in combination of two or more to patients who have active tuberculosis, caused by Mycobacterium tuberculosis?

To reduce the chance that resistant mutants will develop.

_______ is the transfer of bacterial DNA from a donor to recipient via a bacteriophage.

Transduction

______ are segments of DNA that can move from one location to another in a cell's genome.

Transposons

In conjugation in E. coli, an Hfr cell refers to ______.

a cell in which the F plasmid has been integrated into the cell chromosome

A broad-spectrum antimicrobial is most likely effective against ______.

a wide range of both Gram-positive and Gram-negative bacteria

Intercalating agents

act during DNA synthesis AND often result in frameshift mutations.

Choosing the correct antimicrobial procedure depends on many factors including ______.

approval by the Centers for Disease Control and Prevention (CDC) composition of item environmental conditions type and number of microbes composition of item environmental conditions type and number of microbes

Competent cells

are able to take up naked DNA, occur naturally, AND can be created in the laboratory.

It is often difficult to choose which germicide to use because often the most effective options ______.

are not the safest

Many bacteria are able to recognize and destroy invading DNA. It is thought this ability evolved ______.

as a defense against phages

Chemical mutagens that mimic the naturally occurring bases are called

base analogs.

The type of DNA damage repair illustrated here is _______.

base excision repair

Beta-lactamases

break the beta-lactam ring

A bacterial cell described as ___ can take up DNA from the surrounding environment.

competent

Cells that have the ability to take up DNA from the environment are called ______ cells. Multiple choice question.

competent

Sulfonamides work as

competitive inhibitors.

Because viruses have no cell wall, ribosomes, or any other structure targeted by antibiotics, viruses are ______.

completely unaffected by antibiotics

In bacteria, ___ refers to DNA transfer requiring cell to cell contact.

conjugation

Selecting penicillin-resistant mutants by plating them on a medium containing penicillin is an example of ______ selection.

direct

Mutants that can grow under conditions in which the parent (wild type) cells cannot are easily isolated by ___ selection.

direct or positive

Sulfonamide and trimethoprim are both

examples of metabolic inhibitors AND folate inhibitors.

True or false: Antibiotics are completely safe to use.

false

True or false: There are no useful antimicrobials that inhibit nucleic acid synthesis because the processes are essentially the same in both eukaryotic and prokaryotic cells, making the drugs too toxic to humans.

false

True or false: Ultraviolet rays are chemical mutagens.

false

true or false: Prions are easily destroyed by common sterilization procedures.

false

true or false: Viruses are very effectively treated with antibiotics.

false

Among the most useful antibacterial medications that interfere with metabolic pathways are the ___ biosynthesis inhibitors: sulfonamides and trimethoprim.

folate

Resistance to antimicrobials can result from the alteration of existing genes via spontaneous mutation, or via horizontal ___ transfer from another organism.

gene

Match the examples given to the type of method used to control microbial growth.

heat treatment, filtration, irradiation-physical method of control antimicrobial chemical-chemical method of control

Although generally less reliable than heat, germicidal chemicals are especially useful for treating ______.

heat-sensitive items large surfaces

The autoclave treatment may be monitored by

heat-sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus.

To reduce or eliminate disease-/spoilage-causing organisms, food is often treated with

heat. chemical additives. radiation. cold.

With a few exceptions, most of the antiviral drugs that interfere with nucleic acid synthesis are limited to treating infections caused by ______.

herpesviruses rhinoviruses Ebola virus influenza viruses HIV coronaviruses herpesviruses HIV

Disinfectants that destroy all viruses and vegetative organisms but not endospores are referred to as - ___ level disinfectants.

high

Disinfectants that destroy all viruses and vegetative organisms but not endospores are referred to as ___ -level disinfectants.

high

Most antibiotics come from species of bacteria and fungi that normally live _______.

in soils

Ethylene oxide is a gas that

is very useful for sterilizing heat- or moisture-sensitive items.

Adding preservatives such as benzoic acid to food is important because ______.

it inhibits growth of many bacteria and mold

In terms of treating infections in humans, why is the bacterial cell wall such a good drug target for antimicrobials?

it is unique in containing peptidoglycan; antimicrobials that interfere solely with peptidoglycan synthesis do not affect eukaryotic cells.

Microorganisms that are free living are ______ to chemical disinfectants than microorganisms in a biofilm.

less resistant

Because of concerns about antibiotic resistance, the CDC published a document that lists the most serious threats, categorizing them by ______.

level: urgent, serious, and concerning

A solution of sodium hypochlorite is more effective against bacteria at _______ pH.

low

Organisms most fit to survive in a given environment will predominate because they can reproduce more rapidly than others. This phenomenon is called ___

natural selection

The process by which organisms best adapted to a given environment will predominate in that environment is called _______.

natural selection

Alcohols are not reliably effective at destroying

non-enveloped viruses AND endospores.

Virally encoded enzymes required for the assembly and release of viral particles are the targets of medications used totreat certain viral infections. These medications include chemicals called ___ ___ (PIs).

protease inhibitors

When boiling or pasteurizing a sample, microorganisms are destroyed because their ______.

proteins are irreversibly denatured

This image highlights a bacterial defense against invading bacteria called the ___ ___ system

restriction; modification

CRISPR systems involve ______.

retained segments of phage DNA used by bacteria to recognize and destroy future invading DNA

Inhibitors of protein synthesis typically act on

ribosomes

X-rays

cause breaks in DNA molecules.

High pressure (130,000 psi) is thought to kill microbes by altering their ______.

cell membranes proteins

Conjugation in bacteria requires ______.

contact between donor and recipient cell

Mutant cells in bacterial cultures can be isolated by ___ selection and ___ selection methods.

direct; indirect

Only two drugs target viral uncoating, amantadine and rimantadine, which block ___ viruses. Although both prevent or reduce the severity of the disease, their usefulness is limited, because viral strains develop resistance easily.

influenza or influenza A

Flucytosine is taken up by yeast cells and then converted by yeast enzymes to a form that interferes with nucleic acid synthesis by ______.

inhibiting an enzyme required for nucleic acid synthesis

Which is true of aminoglycosides?

They irreversibly bind to the 30S ribosomal subunit AND they are bactericidal.

All of the following are examples of electromagnetic radiation EXCEPT ______.

UV light microwaves X-rays visible light sound waves sound waves

Antibiotics that are most likely to disrupt the normal microbiota are termed

broad-spectrum.

How do aqueous solutions of alcohol usually affect microbes?

by damaging lipid membranes by denaturing proteins

Two methods used to identify mutants in a culture are ______ and ______ selection.

direct; indirect

Certain bacteria are inherently resistant to the effects of some antimicrobials. Inherent resistance is called ___ resistance.

intrinsic

The minimum inhibitory concentration (MIC) is the ______.

lowest concentration of a specific antimicrobial drug needed to prevent the growth of a given bacterial strain in vitro

The major class(es) of antibiotics that inhibit protein synthesis include all of the following EXCEPT

macrolides. aminoglycosides. tetracyclines. bacitracins. streptogramins. bacitracins

Soap generally does not destroy most microbes, but it aids in their ______.

mechanical removal

___ are circular pieces of bacterial DNA that do not usually encode information essential to the life of a cell.

plasmids

A high-solute environment damages microbial cells by causing ______.

plasmolysis

After sulfa drugs and penicillin were introduced, people hoped such drugs would eliminate most bacterial diseases. Unfortunately, this has not happened. Why is this?

Drug resistance limits the usefulness of all known antimicrobials.

The F or fertility plasmid contains genes that are required for bacterial ______.

conjugation

Gene transfer that requires cell-to-cell contact is

conjugation.

A plasmid that can directs its own transfer from donor to recipient cells is called a(n) ___ plasmid.

conjugative

All of the following are examples of mechanisms of acquired antimicrobial drug resistance EXCEPT ______.

development of a mutation in response to an antimicrobial porin proteins preventing or reducing uptake of the drug into the cell production of an enzyme that modifies the drug, inactivating it an alteration in the target molecule, preventing the drug from binding an efflux pump increasing the rate of elimination of a drug from a cell development of a mutation in response to an antimicrobial

A(n) ___, mutation results from an insertion or deletion of nucleotides, leading to a shift of the reading frame from the point of mutation downstream.

Frameshift

True or false: Susceptibility of a pathogen to a specific antimicrobial drug is almost always predictable.

false

A suffix used to describe a killing action would be

-cidal.

True or false: There is a standard antimicrobial procedure available from the Centers for Disease Control and Prevention (CDC) that can be used for all different microorganisms under any condition.

False

_______ does not actually destroy microbes or inhibit their growth but instead removes them physically from samples.

Filtration

_______ is a physical means used for destroying or removing microorganisms.

Filtration

true or false: When you eat food that has been irradiated, you are exposed to radiation.

false

The straining of a fluid or air through a membrane to trap microorganisms is known as ___

filtration

A group of medications called the ___ - ___ drugs are preferred for use against species of Mycobacterium, because they are the most effective as well as the least toxic.

first-line

A common dry heat sterilization method used in the microbiology laboratory is ______.

flaming the inoculating loop

Because nucleic acid synthesis is a common feature of all eukaryotic cells, it is generally a poor target for antifungal drugs. How is the drug flucytosine able to effectively target this process in yeast versus human cells?

It is taken up by yeast and converted by yeast enzymes to an active, inhibitory form

Washing hands with plain soap and water works by ______ removing microbes.

mechanically

All of the following are true statements about antimicrobials EXCEPT ______.

-they are completely safe to use -they have saved countless lives -when properly prescribed and used, they are extremely valuable drugs with lifesaving properties -their benefits, when properly used, dramatically outweigh the risks

Salting and drying decrease the availability of water in food, resulting in an environment that is ______ relative to microbes, thereby preventing their growth.

hypertonic