Brock Microbiology Of Microorganisms Chapter 16

Front 1

RNA Bacteriophages

Back 1

Small RNA genome of these bacterial viruses is translated directly and encodes only a few proteins

Front 2

What conformation do all bacterial RNA viruses have?

Back 2

icosahedral conformation

Front 3

Phage MS2

Back 3

RNA bacteriophage that infects E. coli

genome of a SS "plus sense" strand RNA

can be translated directly upon entry into the host

Front 4

Icosahedral SS DNA Bacteriophages

Back 4

a complementary strand of DNA must be synthesized before transcription can occur

only the (+) strand of DNA is packaged in progeny virions

Front 5

OX174 Bacteriophage

Back 5

circular SS DNA genome

first genetic element shown to have overlapping genes

Front 6

Filamentous SS DNA Bacteriophages

Back 6

have helical symmetry

circular SS DNA genome

infect e. coli

most studied member is phage M13

Front 7

intergenic spaces

Back 7

spaces in filamentous SS DNA bacteriphage genome that do not encode proteins

Front 8

overlapping genes

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1) lysis protein is encoded by a gene that overlaps both the coat protein and the replicase protein

2)parts of the genome are read more than once using different reading frames

3) common in small genomes to allow more efficient use of the limited sized genome

Front 9

Replicative Form (RF)

Back 9

cellular DNA always replicates in the DS configuration

on infection, (+) sense viral DNA becomes separated from the protein coat

when upon entrance into the cell SS DNA converted to double-stranded molecule

Front 10

Assembly of mature M13 virions

Back 10

occurs on the inner surface of the cytoplasmic membrane

end of the M13 virion containing multiple copies of the A-protein is released first with the remainder of the virion following

process of assembly is couples with the budding process

Front 11

Bacteriophage T7

Back 11

DS DNA bacteriophage

have linear genome and icosahedral symmetry

infect e.coli and shigella

has some overlapping genes

Front 12

How is virus multiplication regulated on the T7 chromosome?

Back 12

order of the genes on the T7 chromosome influences the regulation of virus multiplication

T7 DNA injected into the host cell with the genes at the "left end" of the genetic map entering first

Front 13

Mu ("mutator" phage)

Back 13

DS Transposable DNA bacteriophage

introduces mutations into the genome of host genome it is incorporated into

temperate virus "like lambda"

linear genome with icosahedral symmetry

replicates as "transposable element" (TE)

Front 14

Order of transcription of T7

Back 14

T7 uses host RNA polymerase first to transcribe "early proteins" that:

1) protect the virus from digestion by host RE

2) turn off transxription of host genes

3) provide T7 RNA polymerase for recognizing phage promoters that will lead to the transcription of later stage T7 genes

Front 15

Transposable Elements

Back 15

1)sequences of DNA that can move from one location on their host genome to another as discreet genetic units

2) found in both prokaryotes and eukaryotes

3) play an important role in genetic variation

Front 16

Transposase

Back 16

an enzyme that Mu uses to replicate its DNA by transposition

Front 17

Variable end

Back 17

sequence variation in every Mu occurs at this site

results from where the cut is made in the DNA (Mu virion is packaged into the icosahedral head)

each virion is thus genetically unique as result of this

Front 18

G region

Back 18

either (+) [forward] or (-) [inverted]

orientation of this detrmines the kind of tail fibers this phage possesses as a means of adsorption to the host cell

ultimately determines the host range of Mu

Front 19

Replication of Mu

Back 19

1) cuts made using transposase

2) involves DNA at the cut and Mu insertion site

3) 5 bp duplication is typical of Mu replication process

Front 20

Most common morphologies of Archae viruses

Back 20

1) Icosahedral head/tail

2) unusual spindle shaped (not seen in bacteria)

Front 21

Archae viruses (3)

Back 21

1) all archae viruses have DS DNA genomes

2) some are linear while others are circularly permuted

3) genome size of archae viruses is very small

Front 22

Archae virus replication

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1) much less is known compared to viral replication in the bacteria

2) mechanisms are probably similar to those seen in the bacteria

3) little is known regarding the effects archae viruses have on teh genomes of their hosts

Front 23

Differences between prokaryotic and eukaryotic viruses (3)

Back 23

1) Prokaryotes process of transcription and tranlation are coupled while eukaryotes are not

2) prokaryotes can translate polycistronic mRNA while eukaryotic cells cannot

3) transcription occurs in nucleus and translation occurs in cytoplasm in eukaryotes

Front 24

Plant Viruses

Back 24

1) first one found was Tobacco Mosaic Virus (TMV)

2) has helical symmetry

3) single copy of (+) strand RNA genome

4) genome only encodes 4 proteins

Front 25

Chlorella Virus (Chlorella PBCV-1

Back 25

a large, icosahedral virus that has a large DS DNA genome

infects its host and replicates in a fashion similar to the bacteriophages

genomes of chlorella viruses encode several restriction and modification enzymes

Front 26

Chlorella

Back 26

type of green algae

can be infected by a virus called PBCV-1

Front 27

How do the polioviruses and coronaviruses replicate?

Back 27

replicated by conversion of the (+) stranded genome into a (-) stranded intermediate from which new (+) strands are synthesized

Front 28

What is important about the lipid component of chlorella viruses?

Back 28

they are important for infectivity

Front 29

Replication of polio virus

Back 29

1) begins shortly after infection

2) is catalyzed by RNA replicase

3) takes place in cell cytoplasm

Front 30

RNA replicase uses in polio virus replication

Back 30

1) transcribes (+) sense viral RNA into the complementary (-) strand

2) (-) strand is template for repeated transcription of progeny viral (+) strands

3) some of progeny (+) strand may again be transcribed into (-) strand

Front 31

Coronaviruses and SARS

Back 31

SS (+) RNA virus

responsible for a variety of respiratory infections in humans and animals

larger genome size than polio virus (largest of any known RNA virus)

round in shape with glycoprotein spikes protruding outward

Front 32

Negative Strand RNA viruses

Back 32

1) RNA genome itself is a (-) stranded RNA

2) the RNA however is not also the mRNA like in poliovirus

3) examples are Rhabdoviruses (rabies) and Orthomyxoviruses (influenza)

Front 33

Rhabdoviruses (3 characteristics)

Back 33

1) rod shaped

2) nucleocapsid has helical symmetry

3) enveloped viruses with an extensive lipid envelope surrounding nucleocapsid

Front 34

Replication and assembly of Rhabdoviruses

Back 34

1) uses RNA dependent RNA polymerase to covert (-) strand into (+) strand complement

2) RNA is transcribed in the cytoplasm into 2 distinct classes of RNA

Front 35

What two coat proteins are formed during RNA replication of Rhabdoviruses?

Back 35

Nucleocapsid and envelope that is coated with glycoproteins

Front 36

Orthomyxoviruses

Back 36

"myxo" refers to teh fact that these viruses interact with mucus or slime of the cell surface

have envelopes consisting of viral proteins and lipoid derived from host cell

nucleocapsid portion of virus is embedded in the envelope

Front 37

Neuraminidase

Back 37

is another surface protein that breaks down the sialic acid component of hte host cell membrane

otherwise, sialic acid would block viral assembly or beome incorporated into the mature virus particle

Front 38

What two key enzymes do influenza viruses possess?

Back 38

1) RNA dependent RNA polymerase (RNA replicase) [converts (-) stranded genome into a (+) strand

2) RNA endonuclease [cuts a primer form the hots capped mRNA precursors

Front 39

Antigenic Shift

Back 39

portions of the RNA genome from two genetially distinct strains of virus simultaneously infecting the same cell are reasssorted

rearranges the surface proteins from those of the original viruses

these surface proteins ar eth emajor graget of the immune systems antibodies

Front 40

Antigenic Drift

Back 40

occurs when hemagglutinin and neuraminidase proteins become subtly altered by mutations

affects how antibodies are able to recognize virus


usually less dangerous than the effects caused by genetic shift

Front 41

Reoviruses

Back 41

are a family of animal viruses

include rotavirus which can cause respiratory and intestinal infections

consists of linear DS RNA

they contain an RNA dependent RNA polymerase

Front 42

Two steps in Reovirus Replication

Back 42

1) first step is to use the RNA dependent RNA polymerase to make (+) sense mRNA from the (-) strand template

2) mRNA is capped, methylated and then translated

Front 43

Polyomaviruses

Back 43

some types induce tumors in animals (simian virus 40) [SV40]

has no enzymes

genome is a supercoiled circular DS DNA molecule

Front 44

SV40 in the host cell

Back 44

nucleic acid is replicated in the nucleus

proteins are replicated in the cytoplasm

final assembly of the SV40 virion occurs in the nucleus

Front 45

Genetic Map of SV40 genome

Back 45

1) replication of these viruses divide dinto early and late stages

2) early stage- early genes transcribed

3) late stage- late genes transcribed

important mRNA's are transcribed during both stages

Front 46

Polyomaviruses

Back 46

can cause cancer when the viral DNA becomes integrated into a nonpermissive host DNA

can lead to inhibition of cell growth and eventual transformation of a cell to a tumorigenic state

Front 47

Herpesviruses

Back 47

large group of DS DNA viruses

cause a variety of diseases in humans and animals

ability to remain latent in teh body for long periods and become active under stress conditions

Front 48

General Features of Herpesviruses

Back 48

1) structurally complex and consist of 4 distinct morphological units

2) center of virus is called the core (consists of linear DS DNA)

3) icosahedral symmetry of nucleocapside

Front 49

Tegument

Back 49

fibrous layer outside the nucleocapsid in herpesviruses

surrounded bya n envelop that has spikes on teh outer surface

Front 50

Herpes infection and replication

Back 50

virus attaches to receptors of host cell

nucleocapsid then released into cell

transport to the nucleus where viral DNA is uncoated

following infection 3 classes of mRNA are produced

immediate, delayed, late

Front 51

Pox Virus

Back 51

linear DS DNA

among the most complex and largest of animal viruses

virus DNA is syntehsized outside the host cell nucleus

first virus to be studied in detail and to have a vaccine developed for

Front 52

Adenoviruses

Back 52

linear DS DNA

first isolated from human tonsils and adenoids glands

cause mild respiratory infection

replication and DNA syntehsis occurs in the host cell nucleus

Front 53

Two viruses that use reverse transcriptase to replicate

Back 53

1) Retroviruses- have RNA genomes

2) Hepadnaviruses- have DNA genomes

Front 54

Retroviruses

Back 54

have two copies of RNA genome and several enzymes

need these enzymes b/c their RNA genome is not used directly as mRNA

instead, one of the copies of the genome is coverted to DNA by reverse transcriptase and is integrated into the host cell genome

Front 55

3 enzymatic activities of Reverse Transcriptase

Back 55

1) synthesis of DNA from an RNA template

2) Synthesis of DNA from a DNA template

3) Ribonuclease H activity that degrades the RNA strand of a DNA:RNA hybrid

Front 56

Hepadnaviruses

Back 56

hepatitis B virus

very small genomes/structurally

use overlapping enese effectively

is replicated through an RNA intermediate

Front 57

DNA genomes of Hepadnaviruses

Back 57

only partially DS DNA

(+) DNA strand is incomplete and both (+) and (-) strands have gaps

both strands are held together in a circular form by H-bonding of complementary base pairs

Front 58

Viral DNA polymerase possesses these three functions

Back 58

1) DNA Polymerase Activity

2) Reverse Transcriptase Activity

3) Ability to function as a protein primer on the (-) DNA strand