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