Microbio Exam 3 Chapter 13

SARS-COV-2

SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2) — the strain of virus causing the current pandemic

Retroviridae

SINGLE stranded RNA, (2 RNA strands produce DNA) -Contain Reverse transcriptase (which uses RNA as a template to produce complementary double stranded DNA.) --to produce DNA from viral genome. Example RNA viruses: --Lentivirus (HIV) --Oncogenic viruses (includes all RNA tumor viruses)

Host range determined by

Specific host attachment sites and cellular factors

Latent Viral infection

Virus remains in asymptomatic host cell for long periods: cold sores, shingles, HIV.

Growing Viruses

Viruses must be grown in living cells, Bacteriophages form plaques on a lawn of bacteria.

Specialized Transduction

a highly specific part of the host genome is regularly incorporated into the virus. 1) Prophage exists in galactose-using host (containing the gal gene). 2) Phage genome excises, carrying with it the adjacent gal gene from the host. 3) Phage matures and cell lyses, releasing phage carrying gal gene. 4)Phage infects a cell that cannot utilize galactose (lacking gal gene). 5) Along with the prophage, the integrated bacterial gal gene becomes into the new host's DNA. 6) Lysogenic cell can now metabolize galactose.

another name for + strand

sense strand. This can serve as mRNA and go and bind to host cell ribosome to make viral proteins.

Synthesis of proteins and genomes in animal RNA viruses

start: Capsid with Virus (RNA inside) 1) Attachment to host cell. 2) Entry and uncoating 3) RNA replication by viral RNA-dependent RNA polymerase (uses RNA as a template, host cell doesn't have this polymerase). 4) Translation and synthesis of viral proteins 5) Maturation and released

biosynthesis of RNA Viruses

virus multiplies in the host cell's cytoplasm using RNA-dependent RNA polymerase

Pathways of multiplication used by various containing viruses: + Strand

(a) After uncoating, single-stranded RNA (ssRNA) viruses with a + strand genome are able to synthesize proteins directly from their + strand. Using the + strand as a template, they transcribe - strands to produce additional + strands to serve as mRNA and be incorporated into capsid proteins as the viral genome.

Pathways of multiplication used by various containing viruses: - Strand

(b) The ssRNA viruses with a - strand genome must transcribe a + strand to serve as mRNA before they begin synthesizing proteins. The mRNA transcribes additional - strands for incorporation into capsid protein. Both ssRNA and (c) dsRNA viruses must use mRNA (+ strand) to code for proteins, including capsid proteins.

Characteristics of Viruses

- obligatory intracellular parasites (require living host cells to multiply, have no metabolic machinery of their own) - contain DNA or RNA - contain a protein coat - no ribosomes - no ATP-generating mechanism

Viral genome

--RNA could be single stranded RNA: + RNA or -RNA --RNA could be double stranded RNA: (1 plus 1 minus together intertwined) --Could be 2 Single Stranded RNA (not complimentary to each other) + means these can bind to ribosome and get translated. Like the mRNA when they have -RNA, they must make complimentary +RNA to bind to ribosome. -Some will serve as template for more -RNA. --Other will serve to make viral proteins.

Multiplication and inheritance processes of retroviridae

1) Retrovirus enters by fusion between attachment spikes and host cell receptors 2) Uncoating releases 2 viral RNA strands and the viral enzymes reverse transcriptase, integrase, and protease. 3) Reverse Transcriptase copies viral RNA to produce double stranded DNA 4) New viral DNA is transported into host cell nucleus, where integrated into host cell chromosome as a PROVIRUS by viral integrase. The provirus may be replication when host cell replicates. 5) Transcription of the provirus may also occur, producing RNA for new retrovirus genomes and RNA that encodes retrovirus capsid, enzymes, and envelope proteins. 6) Viral proteins are processed by viral protease, some viral proteins moved to host plasma membrane. 7) mature retrovirus leaves host cell, acquiring an envelope and attachment spikes as it buds out.

SARS-CoV-2 Structure

1) Spike protein (S) (attaches ACE-2 receptor) 2) Membrane protein (M) -provides shape 3) Envelope protein (E) -guides assembly and release 4) Nucleocapsid protein (N)-protects RNA 5) RNA viral genome (encodes 29 proteins)

Replication of a DNA-containing animal virus

1) attachment -- virion attaches to host cell 2) entry and uncoating - virion enters cell, and its DNA is uncoated 3) a portion of viral DNA is transcribed, producing mRNA that encodes "early" viral proteins. 4) Biosynthesis - viral DNA is replicated and some viral proteins are made. 5) late translation; capsid proteins are synthesized 6) maturation - virions mature 7) Release - virions are released

How does SARS-CoV-2 infect a cell

1) entry (ACE2) receptors bind to these 2) gets inside and now called endosome. 3) pH drops and membrane opens up (uncoating) to release genome. 4) now in cytoplasm and starts to make viral proteins called peliproteins. 5) Transcription and translation occurs 6) assembly 7) release 8) maturation of new viruses released.

Viral Replication steps

1. Attachment: Phage attaches to host cell 2. Penetration: Phage penetrates host cell and injects DAN 3. Biosynthesis: Phage DNA directs synthesis of viral components by the host cell 4. Maturation: Viral components are assembled into virions 5. Release: Host cell lyses and new virions are released

Culturing Viruses in the Laboratory

1. Culturing viruses in Mature Organisms: In bacteria, and plants and animals 2. Culturing Viruses in embryonated Chicken Eggs --Inexpensive, among the largest of cells, free of contaminiating microbes, and contain a nourishing yolk. 3. Culturing Viruses in Cell (Tissue) Culture

Three mechanisms of entry of animal viruses

1. direct penetration: 2. membrane fusion: 3. endocytosis

First mechanism of entry of animal viruses

1. direct penetration: Virus binds to receptors on cytoplasmic membrane of host cell and penetrates to release it's genome. Typically for naked viruses.

2nd mechanism of entry of animal viruses

2. membrane fusion: for envelope viruses, glycoproteins bind to receptors on cytoplasmic membrane of host and envelope opens up and viral genome now in cytoplasm but then releases capsule.

3rd mechanism of entry of animal viruses

3. Endocytosis, glycoproteins fuse to cytoplasmic membrane. Then envelope has part of the cytoplasmic membrane around virus. now it has to get out of its capsid AND the double coated membrane but it TRICKS the immune system. trojan horse.

Budding

After the sequence of attachment, entry, uncoating, and biosynthesis of viral nucleic acid and protein, the assembled capsid containing nucleic acid pushes through the plasma membrane. As a result, a portion of the plasma membrane, now the envelope, adheres to the virus. This extrusion of a virus from a host cell is one method of release. Budding doesn't kill the host cell immediately, and in some cases the host cell survives. Nonenveloped viruses are released through ruptures in the host cell plasma membrane. In contrast to budding, this type of release usually results in the death of the host cell.

Multiplication of animal viruses

Attachment, Entry, Uncoating, Biosynthesis (or chronic infection first) then release.

Generalized Transduction

Bacterial genes can be picked up in a phage coat and transferred to another bacterium in a process called 1) Phage infects donor bacterial cell 2) Phage DNA and proteins are made, and bacterial chromosome is broken into pieces. 3) Occasionally during phage assembly, pieces of bacterial DNA are packaged in a phage capsid, then donor cell lyses and releases phage particles containing bacterial DNA. 4) Phage carrying bacterial DNA infects a new host cell, the recipient cell. 5) Recombination can occur, producing a recombinant cell wit ha genotype different from both the donor and recipient cells.

COVID-19

COVID-19 (Coronavirus Disease 2019) — the set of symptoms caused by SARS-CoV-2

Corona Virus

Coronavirus (CoV) — a large family of viruses that can cause disease in humans and animals.

Biosynthesis of DNA Viruses

DNA viruses replicate their DNA in the nucleus of the host using viral enzymes Synthesize capsid in the cytoplasm using host cell enzymes

Persistent Infection

Disease processes occurs over a long period generally is fatal, subacute sclerosing (measles, HIV)

Lytic Cycle

a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses 1) Attachment: Phage attaches to host cell. 2) Penetration: Phage penetrates host cell and injects its DNA 3) Biosynthesis: Phage DNA directs synthesis of viral components by the host cell. 4) Maturation: Viral components are assembled into virions. 5) Release: Host cell lyses, and new virions are released.

Lysogenic Cycle

a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA

Lysogenic cycle

a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA 1) Phage attaches to host cell and injects DNA 2) Phage DNA Circularizes and enters lytic cycle or lysogenic cycle 3b) 2) Phage DNA integrates within the bacterial chromosome by recombination, becoming a prophage 3b) the circle can recombine with and become part of the circular bacterial DNA (the lysogenic cycle). The inserted phage DNA is now called a prophage. 4b) Lysogenic bacterium reproduces normally (binary fission) 5) Rare event of prophage may excise from the bacterial chromosome by another recombination and initiate lytic cycle.

another name for - strand

antisense strand. this will need to be copied into a complimentary strand

Acute Infection

comes on rapidly, with severe but short-lived effects