Flashcards in Exam 2 Deck (300):
The complete set of genetic information is the ______, and the functional unit of this is the _____.
What makes up the genome of bacteria?
Chromosomes and plasmids
True or False: Across different species of bacteria, the genome is uniform in size.
False, they vary
What enzyme is responsible for DNA replication?
What enzyme is responsible for transcribing DNA to make mRNA?
What structure is responsible for Translating mRNA to a protein?
The ______ _______ ______ is a site that proteins recognize and bind to on DNA to form a replisome.
Origin of Replication
What happens in DNA replication in bacteria?
-Prior to cell division, two copies of DNA are made, and each daughter cell receives a copy.
_______ replication uses two replication forks and is used to replicate a circular genome.
What happens in semiconservative DNA replication?
The new DNA will contain one original strand and one newly synthesized strand
In what direction is DNA synthesized?
5' --> 3'
What does semidiscontinuous replication mean?
The leading DNA strand is synthesized continuously, while the lagging is synthesized discontinuously as Okazaki fragments
What are three properties of most bacterial DNA?
3. covalently closed
What two things does DNA polymerase need to begin replication?
1. Template strand
______ are the complex of several enzymes and proteins that coordinate replication
What do fluoroquinolones do?
They are antibacterials that target the enzyme DNA gyrase
What two things does RNA polymerase need to begin transcription?
1. A promoter
2. DNA template
After transcription, the new RNA sequence is ______ and ______ to the DNA template strand.
The RNA transcript is the same as which DNA strand and complementary to which strand?
-Same as coding
-complementary to template
Which DNA strand is the (+) or sense strand? Which is the (-) or antisense strand?
-(+) = Coding
-(-) = template
______ disrupts RNA polymerase and causes transcription to end.
What is a sigma factor?
The part of RNA polymerase that recognizes binds to the promoter
What are the four possible products of transcription? Which are stable?
1. Messenger RNA mRNA
2. Ribosomal RNA rRNA (stable)
3. Transfer RNA tRNA (stable)
4. Regulatory RNAs
______ are large complexes that have proteins and rRNA.
What are the four jobs of ribosomes?
1. Maintain the correct reading frame
2. Align the start codon
4. Catalyze peptide bonds between amino acids
Where are ribosomes located in bacteria?
______ deliver the correct amino acids to the ribosome, while aminoacyl-tRNA synthetases do what?
-Attach the correct amino acids to the correct tRNA
What is the open reading frame (ORF)?
-A defined sequence in mRNA where translation is designated to start and stop
The ______ _______ ______ defines that correct start site of translation and sets the reading frame.
Ribosome Binding Site
What does degenerate code mean for the genetic code?
-Several codon sequences will code for the same amino acid
How many reading frames are possible in a strand of mRNA?
Compare and contrast the location and timing of transcription and translation in prokaryotes and eukaryotes.
Prokaryotes: translation and transcription are coupled and occur at the same time, both take place in the cytoplasm
Eukaryotes: Transcription occurs in the nucleus, translation happens in the cytoplasm, do not happen at the same time
Compare and Contrast processing of mRNA in eukaryotes and prokaryotes.
Prokaryotes: no mRNA processing
Eukaryotes: pre-mRNA is processed to mature mRNA by adding a 5' cap and 3' poly (A) tail
Compare and contrast the genes per transcript in eukaryotes and prokaryotes.
Prokaryotes: polycistronic (encodes multiple polypeptides per RNA molecule)
Eukaryotes: Monocistronic (encodes one polypeptide per RNA molecule)
Compare and contrast introns and splicing in prokaryotes and eukaryotes.
Prokaryotes: mRNA does not contain introns
Eukaryotes: mRNA has introns that are removed via splicing
To sense and respond to environmental changes, what two-component regulation method is used?
1. Sensor proteins detect changes in the environment
2. Response regulators initiate the change in gene expression
A _____ is made up of genes transcribed as a polycistronic message.
True or False: An operon is made up of genes that are transcribed as a monocistronic message.
What is a regulon?
The network of genes and operons that are controlled by a common regulatory mechanism
_____ ____ is the chemical signaling that bacteria use to sens or talk to each other
Why is it beneficial for a bacterial cell to use quorum sensing to wait for a critical population density to turn on a gene?
This allows bacteria to be more effective and not waste energy or nutrients. For example, if only a couple bacteria around, they won't waste energy making virulence factors.
What are three examples of gene expression changes as a result of quorum sensing?
3. Motility (flagella)
What are constitutive genes?
Those that are always turned on and typically have an indispensable role in metabolism.
_______ genes are not routinely expressed and are turned on as needed.
True or False: Repressible genes are not routinely expressed ever
False. They are routinely expressed and are turned off as needed
Most genes need to be expressed at different ______ and at different _____.
What are two methods for controlling transcription?
1. Alternative sigma factors
2. DNA-binding proteins
_____ _____ _____ recognize different promoters and control expression of specific groups of genes, called regulons.
Alternative sigma factors
Sigma factors, as well as alternative sigma factors, are a part of what?
___________ are DNA-binding proteins that block transcription, resulting in negative regulation.
How do repressors work?
They bind to an operator, blocking RNA polymerase from transcribing the template DNA
During induction, a ______ molecule _____ repressor binding, turning the gene ______.
During repression, a _____ molecule _____ repressor binding, turning the gene _____.
Repressors result in _____ regulation.
Both DNA-binding proteins and alternative sigma factors are _____.
What is normal for a repressor during induction? Repression?
-In induction, a repressor normally binds to the operator, but an inducer molecule prevents this
-In repression, the repressor alone cannot bind to the DNA, so a corepressor binds and promotes repressor binding
_____ promote transcription and are part of positive regulation.
How do activators work?
Activators bind DNA near the promoter and interact with RNA polymerase
True or False: Inducers work both in activators and repressors.
In induction, inducer molecules promote ______ binding or prevent _____ binding.
An activator is inactive until a _____ molecule binds and makes it functional.
What genes are in the lac operon?
-Genes needed for lactose utilization
What happens to the lac Operon when lactose is and is not present?
-Lactose present: lactose is converted to allolactose, which serves as an inducer and binds to the repressor, preventing it from binding to the operon. The lac genes are turned on
-No lactose: The repressor binds to the operon and prevents transcription. The lac genes are turned off.
Transcription of the lac operon occurs only when ______ levels are low. Why does this happen?
-Glucose is the preferred energy source over lactose
What happens to the lac Operon when glucose is and is not present.
-Glucose present: cAMP levels are low, CAP cannot bind to the DNA, and transcription is not activated. The lac genes are off.
Glucose not present: cAMP levels are high, cAMP binds CAP which binds to a promoter, transcription is activated. The lac genes are on
When glucose levels are low and lactose is present, _____ binds to the repressor, and _____ binds to ____ to bind near a promoter.
What is CAP?
Catabolite Activator Protein
How is diauxic growth seen in E. Coli. in glucose/lactose media?
When the primary energy source, glucose, is used up, there will be a temporary pause in growth as enzymes are made to begin using lactose.
Bacteria are ______, so they only have one copy of a gene with no backup.
A ______ change leads to a change in genotype, which may lead to a change in the ______.
True or False: A phenotypic change always results from a genotypic change.
False, it doesn't guarantee a change in a certain gene
True or False: A change in genotype doesn't guarantee a change in phenotype.
What two ways to bacteria deal with changing environments?
1. Genetic regulation
2. Genetic changes
In bacteria, what are two sources of genetic change?
2. Horizontal Gene transfer
What are the two major types of mutations in bacteria?
1. Base substitution
2. Addition/Deletion (frameshift)
______ _____ mutations are when an incorrect nucleotide is incorporated during DNA synthesis. A _____ mutation is an example, resulting in a single base pair change.
What are the three possible outcomes of a base substitution mutation?
1. Silent mutation (codes for the same amino acid)
2. Missense Mutation (codes for a different amino acid)
3. Nonsense Mutation ( Codes for a Stop codon)
What is a knockout or null mutation?
A mutation that causes a loss of function in the gene and it is inactivated
The addition or deletion of one or two nucleotides causes a _________ mutation.
The addition or deletion of three nucleotides results in what?
The addition or deletion of a codon
Transposons are a type of _____ mutation that encode the enzyme ______.
What are four properties of transposons.
1. Move from one location in the genome to another
2. Can contain additional genes such as antibiotic resistance
3. Will often inactivate the gene that it inserts into
4. Cannot replicate independently
________ mutations occur during normal cell processes. They are random and infrequent, but at characteristic rates.
What is the term for the probability of a mutation with each cell division?
True or False: Mutations are passed onto daughter cells through horizontal gene transfer.
False, vertical gene transfer
______ is when a mutation occurs and then is changed back to the wild-type gene.
Are mutations beneficial?
They can be beneficial if they allow the organism a certain advantage in the environment so that they can better survive and reproduce.
______ mutations occur when an agent damages or changes DNA and increases the mutation rate. The agent that does this is called a ______.
______ mutagens can modify DNA or resemble DNA bases, and often result in _____ _____ mistakes.
Alkylating agents and nitrous acid are a type of ______ mutagen. What do they do?
-change DNA bases
Base analogs are a time of ________ mutagen. What do they do?
-They are nucleotide base "look-alikes" that incorporate into DNA instead of the normal nucleotide base
Why are base substitutions more common in aerobic environments?
In aerobic environments, Reactive Oxygen Species are produced and can damage DNA
_________ ______ are ______ mutagens that insert into the DNA, and can result in frameshift mutations.
How can UV radiation serve as a mutagen? How can X rays serve as a mutagen?
-UV rays induce thymine dimer formation
-X rays can cause a break in the DNA backbone or alter bases
True or False: Light energy can serve as a mutagen.
True (UV radiation)
True or False: Mutations are common, and many are not repaired before cell division.
False, they are rare and are usually repaired
What are the first and second lines of defense for DNA repair mechanisms?
First: DNA polymerase proofreading
Second: DNA repair mechanisms
In DNA repair mechanisms, ______ repair repairs base substitutions, ______ finds and removes oxidized guanine, _______ reverses thymine dimers, and _______ repair cuts out distorted DNA.
What does SOS repair do?
-last-ditch repair mechanism following extensive DNA damage
-Uses recombination and error-prone DNA polymerase
-Increases mutation rate
True or False: In SOS repair, DNA polymerase does not proofread, so DNA synthesis occurs much faster.
What are the 3 methods of horizontal gene transfer?
1. Transformation (naked DNA uptake by bacteria)
2. Transduction (DNA transfer by bacteriophages)
3. Conjugation (direct DNA transfer between bacterial cells)
Transformation, transduction, and conjugation are methods of ______ gene transfer in which the _____ is changed.
DNA transferred through horizontal gene transfer must do one of what two things to be maintained?
1. Have its own origin of replication
2. Be integrated into the chromosome
A ______ is DNA that will be repliated.
In mismatch repair, how do repair enzymes know which strand has the mismatched base?
The template strand is methylated, so repair machinery know the other strand is the new, mismatched strand.
What are four elements of the mobile gene pool?
3. Genomic Islands
4. Phage DNA
What are three properties of plasmids?
1. circular, dsDNA
2. Have an origin of replication and can replicate autommatously
3. Usually code for nonessential genes such as antibiotic resistance
What was Griffith's experiment and what did it prove?
-Used mice and encapsulated cells. Living, encapsulated cells caused death, living, non-encapsulated cells had no effect, heat-killed encapsulated cells had no effect, but heat killed encapsulated cells combined with living non-encapsulated cells cause the moust to die.
-This proved that transformation of DNA between bacterial cells was occurring
Griffith's experiment discovered the _____ of ______.
A _______ cell is capable of DNA uptake. This process is ______.
If an organism takes up DNA from the environment, what is this process called? What must the DNA do?
-DNA must integrate into the host chromosome, unless it is a plasmid with an origin of replication
What is the integration of ssDNA into the chromosome at sites of homology?
What happens in transformation?
-dsDNA from the environment binds to the cell, a single strand enters and the other is degraded, and the single strand interates by homologous recombination into the host chromosome. The strand it replaced is degraded.
After transformation, when a cell divides, what kinds of DNA enter the two daughter cells?
-Because of transformation, one strand is the old strand in the chromosome and one is the new strand. Upon cellular division, one daughter cell gets the old DNA, and one gets the new DNA that may have genetic advantage such as antibiotic resistance
What are the two types of transduction by bacteriophages?
1. Generalized transduction (any genes of donor cell can be transferred)
2. Specialized transduction (only specific genes of the donor cell can be transferred)
Generalized transduction is due to what? What is the result?
-Due to packaging error during phage assembly
-Host DNA fragments are mistakenly packaged into some phage head
A transducing particle has ______ DNA.
What genes can be transferred in generalized transduction?
What can a transducing particle do?
-Infect a new host
-new DNA can integrate into host chromosome via homologous recombination
Specialized transduction is due to what? What is the result? What can the new phage do?
-Due to mistakes during excision of a temperate phage
-Some flaking bacterial DNA is taken along with phage DNA
-The new phage can infect a new host, and the DNA can integrate in the host chromosome via homologous recombination
In specialized transduction, what genes are transferred?
-only genes adjacent to the integrated phage DNA
Conjugation requires ______ between bacterial cells.
_______ _____ direct there own transfer in conjugation.
What are the two types of conjugation?
1. Plasmid transfer
2. chromosome transfer
The _____ plasmid is a conjugative plasmid. It encodes proteins that _____ transfer.
In conjugation, the F+ cell is the ______ cell, and the F- cell is the ______ cell.
What happens in conjugation of a plasmid?
-The F pilus contacts the F- recipient cell, the pilus retracts and pulls the two cells together as one strand of the F plasmid is cut at the origin of transfer, a single strand of the F plasmid is transferred to the F- cell, a complement strand is synthesized, and then both the Donor and recipient are F+
In ______ cells, the F plasmid is integrated into the chromosome via homologous recombination.
True or False: In Hfr cells, the F plasmid can be excised, and no host chromosome will be taken.
False, a portion of the chromosome can be excised with it
What happens during conjugation of a chromosome?
The Hfr cells produces an F pilus, part of the chromosome is transferred to an F- cell as a single strand, the cells separate and the chromosome breaks so only a portion is transferred, the DNA integrates into the host chromosome via homologous recombination, and the cell remains F- since transfer was incomplete
F- cells can become F+ cells after ____ transfer in conjugation.
When do genetic changes become predominant in the population?
If they are selected for or if they provide growth or reproductive advantages
In direct selection of mutants, the mutant grows in _______ _____ conditions
If you want to use direct selection for a streptomycin-resistant mutant, what should you add to the media and why?
-Only resistant bacteria will grow
In _______ selection, the mutant cannot grow in selective media conditions. This requires _____ ____ to isolate the mutant.
______ _____ are large fragments of DNA in a chromosome or plasmid that code for genes that allow the cell to occupy specific environmental locations.
Viruses are ______ intracellular parasites.
True or False: Viruses are living infectious agents.
False, they are infectious agents, but not living
Why are viruses difficult to study? Why are bacteriophages important to study?
-Difficult: require live host cells and most can't be seen with light microcopy
-Important: model systems, vehicles for horizontal gene transfer, and they affect environmental bacterial populations
A ______ is a viral particle.
What is a naked virus?
A non-enveloped virus that has a nucleocapsid only and is more resistant to disinfectants and antibiotics
What is an enveloped virus?
A virus that has its nucleocapsid enclosed in a lipid bilayer
Which kind of virus, enveloped or naked, is more susceptible to disinectants and the environment and why?
-Disinfectants target the envelope. If they loose this, they also loose spike proteins and can no longer attach to the host
What are the two major categories of viruses?
Enveloped and naked
What are two structures used for host cell attachment in viruses?
1. Spike proteins
2. Tail fibers
Spike proteins attach to the _____ of naked viruses and the ______ of enveloped viruses.
What two things comprise the nucleocapsid?
1. Nucleic acid
The capsid is made of identical protein subunits called ______ and these determine the _____ of the virus.
What are three common shapes of viruses?
True or false: The envelope of the virus determines its shape.
False, the capsomeres do
In viral taxonomy, what are the two main things that the International Committee on Viral Taxonomy use to classify viruses?
1. Genome structure
Viruses are also informally named and grouped on the bases of _____ _____ ___.
Route of Transmission
The two types of viral infections are _____ infection and _____ state.
What happens in a productive infection? What are the two outcomes?
-More virus is produced
1. The host cell lyses and releases virions, and the host cell dies
2. The host cell multiplies and continually releases virions
What is a latent state infection? What is the outcome?
-The virus nucleic acid integrates into the host genome or replicates as a plasmid
-The host cell multiplies but the phenotype is often changed because of viral genes
What are the three types of baceriophages?
1. Lytic Phage
2. Temperate Phage
3. Filamentous Phage
A ____ phage results from a productive infection in which the virulent phage exits the host and the host cell lyses, resulting in death.
Describe the infection cycle of a T4 Lytic Phage.
1. Tail fibers bind to a bacterial receptor
2. The phage lysozome degrades the bacterial cell wall. The tail contracts and injects the genome
3. Early proteins are produced that degrade host DNA and modify host RNA polymerase. Late proteins are produced and are the structural components of the new phage to be assembled
4. Assembly of a new phage
5. Lysozyme is produced in late infection to release the new phage particles
Temperate phages can have what two life cycles?
In a _____ infection, phage DNA is incorporated into the host genome, and the phage remains latent.
A ____ is a host cell with phage DNA incorporated into the genome.
What is prophage?
Phage DNA that, in a temperate infection, has integrated into the host genome
Prophage can ____ with the host chromosome or be ____ by a phage-encoded enzyme resulting in lytic growth.
How is lysogenic growth maintained?
A transcriptional repressor protein that is phage encoded prevents the expression of lytic genes that will cause the prophage to be excised from the host chromosome
What happens in phage induction?
In a temperate infection, if the host cell experiences DNA damage so that the SOS repair system is activated, the repressor protein is cleaved, lytic genes are turned on, and the phage turns to the lytic cycle and excapes the host
In a lytic phage, packaging errors during assembly can result in _____ ____.
In a temperate phage, inaccurate excision of the phage DNA can result in _________ _______.
What are two outcomes of lysogeny in a temperate phage?
1. Immunity to superinfection (the lysogen is immune to infection by the same or related phage)
2. Lysogenic Conversion (Lysogen changes the host cell's phenotype)
Filamentous phage infections cause ____ infections. Howerver, the host cell is not _____ and grows more _____.
What is the infection cycle like for filamentous phages?
1. The phage attaches to an F pilus on the host
2. The phage genome is injected and a complementary strand is made
3.Phage DNA replicates
4. Phage capsomeres are synthesized and embedded into the host cell membrane so that the phage nucleic acid gains its capsid as it exits the host
In filmentouts phages, ______ ______ DNA enter the host, then a complementary strand is formed. After the complementary strand is formed, the DNA is in its ______ form.
In a filamentous phage, as the phage exits the host, no cell ____ occurs and the _____ is formed around the phage.
What are three methods of bacterial defenses against viral infection?
1.Prevent Phage attachment by altering or covering receptors
2. Restriction-modification systems
3. CRISPR System
In restriction-modification systems, bacteria _____ incoming DNA. _____ _____ recognize short sequences and cut foreign DNA, and DNA _____ is used to distinguish self from non-self.
What does CRISPR stand for?
Clusters of Regularly Interspaced Short Palindromic Repeats
How is the CRISPR system used to defend bacteria against viruses?
Fragments of phage DNA, called spacer sequences, are stored in an area of the host chromosome called the CRISPR array. The CRISPR array is transcribed and binds to CAS proteins. The the CRISPR array and CAS protein complex bind to incoming phage DNA, it is targeted for degradation
What is the five step infection cycle of animal viruses?
1. Attachment ( viruses bind to receptors on the plama membrane of the host)
2. Penetration and uncoating of the viral genome by fursion or endocytosis
3. Synthesis and expression of viral genes to produce viral structures and make multiple copies of the genome
4. Assembly of the protein capsid and packaging of the genome
5.Release through budding or apoptosis
Attachment of animal viruses to the host requires receptors, which are usually _______.
How can naked viruses penetrate the host and uncoat their genome? How do enveloped viruses?
-Naked viruses must enter via endocytosis
-Enveloped viruses can enter via endocytosis or fusion because their envelope can fuse with the host cell membrane
How do double stranded DNA viruses replicate?
In the nucleus, they use host DNA polymerases to make mRNA and then make proteins, and to make more dsDNA
How do single stranded (-) DNA viruses replicate?
In the nucleus, they synthesize a complementary (+) coding strand. Then the dsDNA uses host DNA polymerase to make mRNA and proteins, and more ssDNA (-)
How do single stranded (+) DNA viruses replicate?
In the nucleus, they synthesize the complementary (-) strand. Then, the dsDNA uses host DNA polymerase to make mRNA and proteins, and more ssDNA (+)
In dsDNA, the ____ strand is the template strand and the _____ strand is the coding strand.
What is the advantage to DNA viruses that encode their own DNA polymerase?
-DNA polymerase is only made by the host during replication, so viruses that hijack host DNA polymerase have to wait until host replication occurs. dsDNA that synthesizes its own DNA polymerase does not have to wait for host replication.
For DNA viruses, replication usually occurs in the ________.
What is replicase?
RNA dependent RNA polymerase with no proofreading mechanisms, resulting in frequent mutation
How do ssRNA (+) viruses replicate?
The (+) strand is the mRNA, and can directly make proteins. Replicase is a protein that is made that can synthesize the (-) strand.
How do ssRNA (-) viruses replicate?
-ssRNA (-) viruses package replicase so that the (+) strand can be synthesized and used in protein synthesis
How do dsRNA viruses replicate?
-The (+) mRNA strand is synthesized by replicase and can make proteins.
The ____ genome strand is mRNA.
RNA virus replication usually occurs in the ___ and uses virus encoded ______ for genome replication.
How do reverse transcribing viruses replicate?
Viral encoded Reverse transcriptase is used to make ss(-) DNA from the ss (+) RNA. The viruse uses host machinery to synthesize a complementary strand, and the dsDNA is integrated into the host genome. The original ss( +) RNA also serves as mRNA to make proteins.
Reverse transcriptase is an ezyme unique to _____ ____ viruses and ______. What does this enzyme do?
-It is an RNA dependent DNA polymerase used for DNA synthesis
Reverse transcribing viruses are also called ______.
How are naked viruses released from the host? How are enveloped viruses released?
-Naked: released when the host dies through apoptosis
-Enveloped: Released by budding to obtain its envelope from the host
True or False: Some viruses obtain their envelope from host organelles such as the golgi?
A RNA virus has no _____ intermediate, and goes from _____ to ____.
-RNA to RNA
A retrovirus has a _____ intermediate and goes from _____ to _____ to______.
-RNA to DNA to RNA
A retrovirus uses reverse transcriptase in the ______ to get DNA. Then, the DNA travels to the ______ and is incorporated into the host _______.
When double stranded DNA is made in reverse transcribing viruses, what happens to it?
It incorporates into the host cell genome and undergoes latency.
What does viral dsDNA use to replicate its genome? What does it use to express genes?
-Host DNA polymerase
-Host RNA polymerase and host ribosomes
What does viral ss(+) DNA use to replicate its genome? What does it use to express genes?
-Host DNA polymerase
-Host RNA polymerase and host ribosomes
What does dsDNA with DNA polymerase and RNA polymerase genes need to replicate its genome? What does it need to express its genes?
-Viral DNA polymerase
-Viral RNA polymerase
What does ss(+)RNA need to replicate its genome? What does it need to express its genes?
-The (+) strand serves as mRNA
What does ss(-)RNA need to replicate its genome? What does it need to express its genes?
-Viral replicase that is packaged with the virus
-The (+) strand serves as mRNA
What does a ss(+)RNA retrovirus need to replicate its genome? What does it need to express its genes?
-To go from RNA to DNA, viral reverse transcriptase is needed.
-To go from DNA to mRNA, host RNA polymerase is needed
True or False: Viruses have ribosomes.
False, viruses do not have ribosomes
Virus evolution can be a result of _____ and ______.
1. Reassortment through coinfection
2. Recombination with the host chromosome
Antigenic _____ results from mutations in surface proteins that are recognized by the host immune system. _____ ____ causes this strain of the virus to be more successful.
True or False: Because small mutations constantly occur resulting in new strains of viruses, antigenic shift occurs and this is why you need a new flu shot every year.
False, antigenic drift
_____ causes antigenic shift, where different strains or viruses with ____ genomes coinfect a host and a new virus is made.
What are three properties of an acute infection? Give an example of one
1. Rapid onset
2. Short duration
3. Virus is cleared after the disease ends
What are two kinds of persistent infection?
A chronic infection has no lasting _______, but viral ____ are continuously produced after the initial infection
True or False: The initial infection of a chronic virus can occur with or without symptoms.
In a ______ infection, after the initial infection the virus lays _____ in the host. At this stage, what are properties of the virus? Give an example.
-Non-infectious, can't be eliminated, can be reactivated, and symptoms can reemerge
A ______ is abnormal cell growth.
____________ stimulate cell division. _______ inhibit cell division.
-Tumor supressor genese
Viral ____ are mostly DNA viruses and can interfere with host control, stimulating cell growth and inducing tumors.
____ infections can lead to tumors.
_____ ____ are used to measure the growth of phage particles. To count growth, you count ____ _____ ______.
-Plaque forming units
True or False: Viruses can be growin in any living cells.
False, they must be grown in their appropriate host cell
When quantitating animal viruses, ____ ____ can be used for cultured cells, and ____ ____ can be used via electron microscopy. ____ ____ can be used to get the viral titer. _______ can be used to see the relative concentration of virions.
A _____ ____ is the concentration of virions.
What are three properties of viroids?
1. Small circular RNAs
2. No protein
3. Only found in plants
Prions are infectious ____ agents that cause ____ _____ human and animal diseases. They cause _______ ______ .
True or False: Prions are usually species specific in transmission
Prions are ______ and normal proteins are _____.
How do prions cause harm to the host?
They cause normally folded proteins to misfold
Can bacteriophages infect via fusion?
No, bacteria have a cell wall which does not allow for fusion
Who was the British physician who began sterilizing instruments and maintaining clean operating environments?
_____ is the removal of all organisms including endospores and viruses. ______ is the elimination of most or all pathogens.
What are the two types of disinfection methods and what are they used on?
1. Disifectants (inanimate objects)
2.Antiseptics (living tissues)
What do bactericidal agents do to bacteria? What do bacteriostatic agents do?
-Bacteriostatic: Slow growth
______ is used to reduce pathogens to levels considered safe to handle through hand washing, heat or disinfectants. ______ is one method of this to reduce microbe populations.
______ delays food spoilage by adjusting conditions or adding _______ preservatives. ______ is one method of this which uses brief heating to reduce the number of spoilage organisms and destroy pathogens.
In daily life, what two things are good for microbial growth control?
-Washing and scrubbing with soaps and detergents
Why can washing and scrubbing help control growth?
It is mechanical removal of microbes
What are nosocomial infections?
Healthcare associated infections
In hospitals and healthcare facilities, ____ are more likely to be encountered. Instruments must be_______.
In the microbiology laboratory, the goal is to prevent ____. Because of this, ______, _____, and ____ ____ are used.
The goal of controlling microbial growth in food production is to retain _____ of perishables and prevent _____.
In food production, what is the most common and reliable method to control microbial growth?
The goal of water treatment is to ensure drinking water is free of _______. What is used? What are the drawbacks of this method?
-Can make disinfection by-products and some organisms are resistant to chlorine
When choosing a procedure to reduce microbial growth, what four things should be considered?
1. type and number of microbes present
2. environmental conditions
3. Risk for infection
4. Composition of item
When looking at the types of microbes present to decide a good procedure to limit microbial growth, ______ resistance should be considered.
Why should the number of organisms be considered while choosing an appropriate method to limit microbial growth?
The population size can affect the time it takes the chemicals or heat to kill the microbes
How does handwashing reduces the time it takes heat or chemicals to kill microbes?
The mechanical action removes some of the microbial load
What is the Decimal Reduction Time (D value)?
Gauges the effectiveness of a chemical or procedure by measuring the time required to kill 90% of a microbial population
What does "D121 for 10 minutes" mean?
This is the D value and means it takes 10 minutes at 121 degrees to kill 90% of the micribial population
What kinds of environmental conditions need to be considered when choosing a method to reduce a microbial population?
Dirt, grease, body fluids, pH, temperature
Medical equipment is categorized according to what?
Risk of infection
What are the three categories of medical equipment?
1. Critical- contacts body tissues so it must be sterile
2. Semicritical- contacts mucous membranes but doest not penetrate, so it must be free of viruses and vegetative bacteria
3. Non-Critical- Contacts only unbroken skin and must be sanitized
When considering which method is best to reduce the microbial population, _____ of the item must be considered since some methods are inappropriate for certain items.
What are four physical methods to reduce microbial growth?
4. Pressure (no heat)
_____ heat irreversibly denatures proteins._____ is one method of this that is useful for the treatment of drinking water. _____ is another method that reduces the number of heat sensitive pathogens and spoilage organisms. Nether method ______.
Pasteurization involves brief ____ and rapid _____. What are the two methods?
-High temperature, short time (most products)
-Ultra-high temperature (Shelf-stable drinks)
The only moist heat method that sterilizes is ____ ____, also known as ______. How does it do this?
-Using pressurized steam, the temperature raises and can kill endospores
Commercial canning uses an industrial size autoclave,called a ______. This makes canning food commercially _____.
Which is less effective: Dry heat or moist heat? Why?
-Longer times and higher temperatures needed to sterilize
What are two methods of dry heat? What do they work on?
-Hot air ovens for dry material
- Incineration for sterilizing and destroying animal wastes and carcasses
What is the only method of dry heat sterilization?
Most filtration retains ______ ____. What are two methods of filtration?
-Filtration of fluids
-Filtration of air
What are two methods for filtration of fluids? Do they sterilize?
-Membrane filters (smaller pores)
-Depth filters (larger pores)
These can sterilize if done properly
A common method in hospitals of air filtration of air is ______. What can this method be combined with?
-HEPA (high-efficiency particulate air)
-Electrostatic filters and UV
What are three methods of radiation?
1.Ionizing radiation (gamma rays, X-rays)
2. Ultraviolet Radiation
What are three properties of ionizing radiation?
1. Destroys DNA and maybe membrane
2. Produces ROS
_____ radiation damages DNA, and kills microbes in the air and on surfaces. What are the limitations of this method?
-It is only a surface treatment because most it has poor penetration through solids or turbid liquids
____ is a radiation method that doesn't kill directly, but generates a moist heat. It heats unevenly, so cells often survive.
Which method destroy microbes by denaturing proteins and altering cell permeability? What industry is this used in and what is the advantage?
-High Pressure (without heat)
-Commercial fresh foods
-Maintains color and flavor while avoiding problems with high temperature
What are chemicals useful for? What do they target?
-Useful for large surfaces and heat-sensitive items
-Target proteins, DNA, membranes, or viral envelopes
What do sterilants destroy? What are they used on?
-destroy all microbes
-Used on critical instruments
What are the levels of disinfectants?
-High level (destroys viruses and vegetative cells, but not endospores. Used on semi-critical instruments)
-Intermediate level (Destroys vegetative bacteria, mycobacteria and fungi, but not all viruses or endospore. Used on non-critical instruments)
-Low level (Destroy vegetative bacteria, fungi, and enveloped viruses. Used on floors, furniture, and walls)
When selecting the right chemical to use, you must consider what's _____ and _____.
_____ are cheap and available, but rapidly evaportate which limits contact time and do no reliably kill endospores. Are the antiseptic or do they sterilize?
________ destroy all or most microbes and they are effective and fast working, but they are an irritant, a suspected carcinogen, and toxic. Can they be used as an antiseptic or to disinfect?
_________ have low toxicity, destroy most microbes, have good contact time, but they cause severe allergic reactions. Are the used to sterilize or as an antiseptic?-
_____ _____ _____ penetrate hard to reach places and don't damage moisture-sensitive materials, but they are toxic, explosive, possibly carcinogenic, expensive and not readily available. Can they be used as an antiseptic or to sterlize?
-Ethylene oxide gas
What can alcohols be used for?
As an prior to a procedure that will break skin or as a treatment for some instruments
What can aldehydes be used for?
Can sterilize medical equipment or preserve biological specimens
What can binguanides be used for?
As an antiseptic in soaps, lotions, and mouthwash
What can ethylene oxide gas be used for?
To sterilize medical devices that are moisture or heat sensitive as well as blankets and pillows
______ are cheap, readily available, kill most pathogens, but can be toxic, corrosive, inactive, and to not kill endospores. Can they be used as an antiseptic or to sterilize?
-Chlorine disinfects, Iodine can be used as an antiseptic, and ClO2 gas can sterilize
______ are effective, inactivate enzymes and other proteins, but high concentrations are often toxic and wide use can pollute water
What are metals used for?
Topical dressings for burns and wounds
_______ is a powerful oxidizing agent, decomposes quickly, is generated on-site, and requires expensive equipment. What are uses?
-Alternative to chlorine for disinfecting drinking water, waste water, and public swimming pools
______ are powerful oxidizers, are biodegradable, have no residue, little damage, and low toxicity, but the effectiveness depends on the surface, they are not stable, and can be broken down by catalases from microbes. Are they antiseptics or sterilants?
-Can be antiseptic or sterilant
What are peroxygens used for?
-Hydrogen peroxide is used as an antiseptic and to sterilize inanimate objects
-Paracetic acid is used to sterilize medical devices
________ are one of the earliest disinfectants, they have low cost, destroy membranes, denature proteins, and kill most vegetative bacteria. However they have an unpleasent odor, irritate skin, leaves residue, are not reliable on endospores, and can be toxic.
What was a common phenolics that used to be in soaps, lotions, toothpaste, and many personal care products and is now banned? Why was it banned?
Triclosan, to prevent microbial resistance
_____ _____ _______ are non-toxic, cationic, destroy membranes of vegetative bacteria and viral envelopes, are not effective against endospores, mycobacteria, or naked viruses, and are inactivated by anionic soaps and detergents. What are they used for?
-Quaternary Ammonium Compounds (Quats)
-Used to disinfect food preparation surfaces and are found in healthcare products, also they are a detergent that aid in the removal of dirt and organic matter
Disinfectants and antiseptics can provide _____ _______ for microbes to acquire ______ _____. This is _____ resistance.
What do efflux pumps do?
Expel chemical disinfectants
What is the goal of preservation disinfectants?
To prevent or slow the growth of microbes in order to extend shelf life
Chemical preservatives used in the food industry must be _____ ____. What are two examples?
-Weak organic acids
-Nitrate and Nitrite
How do nitrate and nitrite work as a chemical preservative?
They inhibit endospore formation and vegetative cell growth
______ and ______ are two methods of low-temperature storage for preservation. ______ slows or stops enzyme functions, while ____ stops all microbial growth.
-Refrigeration and freezing
What are two methods of reducing water availability to preserve food?
-Sugars and salts at high concentrations
-Drying foods or lyophilization (freeze-drying)
Many preservation methods are _________. They do not reliably kill cells, they only slow the growth.