Microbiology Chapter 13
lytic infection vs. lysogenic
lytic infections are productive, while lysogenic is a latent infection
Temperate phages are those that can enter either the ________ or ________ cycle.
lytic or lysogenic
Infection of bacteria by _________ phages always ends with the lysis of the host cell.
lytic, T4, or virulent
COVID-19 named for it's..
morphology, "corona" meaning crown, which is the shape of this virus particle
Diazotrophs
nitrogen fixing bacteria -azotobacter
"Kill the Winner" Hypothesis
"Winners" are bacteria that have achieved sufficient #s to reach relatively high densities Whichever virus is doing the best (winning) gets killed/dies off Total number of viruses and bacteria remain relatively constant but concentration of individual species vary.
Titer
number of infectious units per volume of fluid -concentration of phage in the original sample -counting plates yields the titer
_______ are viruses that are capable of infecting and selectively killing cancer cells.
oncolytic
viruses are commonly referred to by
only their species name
E. coli makes ________ colonies when plated
pink
In a(n) ______, viral titer can be determined by counting clear zones in a monolayer of cells
plaque assay
virus translates to..
poison
Genome entry phase
powerpoint
Prions are composed of ________.
protein only
The stage of viral multiplication at which budding occurs is ______.
release
filamentous phages
single stranded DNA phages that look like long fibers, cause infections but process doesn't kill host cell 1. Phage attaches to the F pilus of a bacterial cell and injects its single-stranded DNA 2. Phage DNA replicates; phage capsomeres are synthesized and embedded in the host membrane 3. split and have two carrier cells -M13 phage is useful in certain recombinant DNA procedures
Attachment of animal viruses to the host cell typically occurs by means of ______.
spikes
this phage can either cause a lytic infection or can incorporate its DNA into the host genome as a prophage.
temperate phage
Bacteriophages that can enter into a lytic cycle or a lysogenic cycle are called
temperate phages
Virulence
the extent of pathogenicity
In acute viral infections, although the infected host cells may die, the host may survive because ______.
the host's immune system may gradually eliminate the virus
lytic infections
type of infection in which a virus enters a cell, makes copies of itself, and causes the cell to burst -productive or virulent infections
without a host, viruses have..
-no motility -no metabolism -no replication
virus families end in suffix
-viridae
genus ends in
-virus
lysogenic cycle
A phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host.
GC content is directly related to _________
AT content
plaque assays (method used to study bacteriophages)
used to count phage particles in samples: sewage, sea water, soil
Transmissible Spongiform Encephalopathies
Caused by only prions -Bovine spongiform encephalopathy (mad cow disease) -Chronic and fatal -brain function deteriorates -tissues develop holes -neurons die
example of prion disease in the US
Chronic wasting disease - has jumped to humans in the past
GC content is also related to __________ in PCR
DNA denaturing
Synthesis Phase
DNA replication
Which form of transduction results from packaging errors during phage assembly?
Generalized
what are other names for the filamentous phage?
M13, Temperate, and lysogenic
Real-time PCR
Newly made DNA tagged with a fluorescent dye; the levels of fluorescence can be measured after every PCR cycle quantitatively
Which test is most accurate for COVID-19?
PCR is the most specific test for COVID-19 detection
which types of viruses mutate faster: RNA or DNA?
RNA due to the lack of proof reading that is present with DNA viruses with DNA polymerase. RNA polymerase does not proofread.
why is washing with soap an effective way to remove SARS-CoV-2?
Soap destroys the lipid bilayer of the particle
Which form of transduction results from excision errors during the transition from a lysogenic to lytic cycle?
Specialized
GC content is useful for
Species identification in bacteria
tobacco mosaic disease
The first virus discovered in 1883 by german Adolf Meyer, it stunts the growth of Tobacco plants and gives them a mottled coloration. -D.M. Iwanowsky, Martinus Beijerinck determined it was caused by "filterable virus" too small to be seen with light microscope, passed through filters for bacteria
True or False. Prophages can provide benefits to the host bacterium while they are dormant.
True
viruses can have their own virus. true or false.
True; example: sputnik is virus of mimivirus
DNA viruses
Usually double stranded (ds) but may be single stranded (ss) Circular or linear
RNA viruses
Usually single stranded, may be double stranded, may be segmented into separate RNA pieces
The major categories of animal viral infections are _________ infections, characterized by the sudden onset of symptoms of a relatively short duration, and ________ infections that can continue with or without symptoms for years.
acute; persistent
phage induction
allows phage to escape damaged host
End point PCR
analysis after all PCR cycles have completed agarose gel electrophoresis and staining on PCR product
plaques
areas where virus-infected cells have been destroyed and show up as a clear, well-defined patches in the cell sheet
assembly phase
assembly of capsids and packaging of viral genomes into new virions (maturation)
spikes
attach to receptor sites on the host cell; phages attach by tail fibers
persistent infections can be _____ or ______
chronic or latent
If viruses are present in high enough concentrations in a sample, they can be quantified directly using a(n) _______ microscope.
electron
plant viruses
enter through wounds or via insects Plant cells are generally protected from disease by an impermeable cell wall -rarely recover from viral infection -insects (pollinators) become primary vectors of transmission
T4 phage (dsDNA)
entire process takes 30 minutes
Which types of viruses are released by budding?
enveloped viruses
virulent
extremely poisonous
GC content refers to the
fraction of G and C nucleotides in the genome.
In the case of animal viruses, the molecules that viral spikes attach to on the host cell in order to gain entry are typically ______.
glycoproteins
E. coli is Gram
gram negative
All of the following are required for synthesis of new virus particles in a host cell EXCEPT ______.
homologous recombination
Viruses are best described as _______.
infectious agents or obligate intracellular parasites
other characteristics for viral taxonomy
viral shape and diseases
A _______ is a single virus particle.
virion
Bacteriophages that exit the host cell at the end of an infection by lysing it are called _______ phages.
virulent or LYTIC
bacteriophages
viruses that infect bacteria
viroids have only been found in _______
plants -usually only transmitted in a specific species
Arboviruses
arthropod-borne viruses
Pandoravirus
-Infects amoebas -Giant virus -Large virus @ 1 𝜇m, larger than some bacteria -Largest genome of any known virus
oral-fecal route viral transmission are referred to by
enteric viruses
generalized transduction
excision mistake during transition from lysogenic to lytic cycle of temperate phage -lytic cycle accidentally places host DNA into a phage, which is brought to another cell -transducing particle
Virion
nucleic acid surrounded by a capsid protein coat
What term is used to describe the transfer of genetic information from one bacterium to another bacterium by a bacteriophage?
transduction
what type of horizontal gene transfer do bacteriophage use?
transduction (look into this more)
zoonotic viruses
transmitted from animal to human via animal vector
generalized infection cycle of animal viruses: (5)
1. attachment 2. genome entry 3. synthesis or biosynthesis 4. assembly 5. release
List the steps of an animal virus infection cycle
1. attachment 2. penetration and uncoating 3. synthesis of viral proteins and replication of the genome 4. assembly 5. release
pros of real time PCR
1. detect active infections 2. quick and easy to define targets and design primers 3. can work from simple tissue swabs or sputum
what are the 2 types of animal virus entry?
1. entry by membrane fusion 2. entry by endocytosis
Animal viruses can be studied by infecting ______. (3)
1. fertilized chicken eggs 2. live animals 3. cell or tissue culture
Viral Taxonomy key characteristics include: (2)
1. genome structure (nucleic acid and strandedness) 2. hosts infected
lysogenic conversion
a change in the properties of a bacterium conferred by a prophage (only these have toxins)
in a lab, a virus needs what at least once in it's growth and replication?
a host
What is a virus?
a tiny, nonliving, particle that enters and reproduces inside a living cell
reverse transcriptase
can be used in PCR of the RNA virus COVID-19
Animal viruses ______.
can only be grown in animal cells
Why are bacteriophages easier to study than animal viruses?
it is easier to grow bacterial cells than animal cells in a lab
what microscope does not show viral particles?
light microscopy
false negative
low sensitivity test
false positive
low specificity test
release phase
lysis and/or budding occurs, viruses leave cell
infection cycle
the route of transmission an organism takes to infect additional hosts
when viruses mutate very quickly, what happens in relation to testing for that virus?
the tests can come back negative due to the low specificity and the changing virus
prophage
the viral DNA that is embedded in the host cell's DNA
every 10,000 replications in lysogenic cycle..
there is a lytic production
why are bacteriophage medically important?
they can be used to rid hosts of viral infections
why are plant viruses important?
they can cause major economic effects
Human cells are larger than viruses by which size factor?
thousand
Bacteriophages play a fundamental role in a type of horizontal gene transfer called _______
transduction
3 general types of bacteriophages
1. lytic (virulent) phages 2. temperature phages 3. filamentous phages
How are viruses classified? (5)
1. morphology 2. genome material 3. type of replication 4. host 5. type of disease (newly) genome sequencing
Which are types of relationships that bacteriophages can have with their host?(2)
1. productive lytic phase 2. latent infection where host cell genome is changed
when testing for COVID-19, what two factors are most important?
1. specificity 2. timing of test
3 traits of acute infections
1. rapid onset/ short duration 2. burst of visions released from infected host cell 3. immune system gradually eliminates virus
what is true of viruses? (2)
1. viral capsid is made of proteins 2. viruses contain RNA or DNA but not both
arrange in order of smallest to largest: eukaryotic cells, bacterial cells, viral particles
1. viral particles 2. bacterial cells 3. eukaryotic cells
The smallest virus is approximately what size?
10 Nanometers