Microbiology Chapter 13

What is a nucleocapsid?

the nucleic acid and capsid in a vision. Some contain a phospholipid envelope. The outer most layer provides protection and recognition sites for host cells.

Describe animal virus?

Same basic replication pathway as bacteriophages. Differences result from 1. presence of envelope around same viruses. 2. eukaryotic nature of animal cells. 3. Lack of cell wall in animal cells. Attachment of animal virus. Chemical attraction and exact fit between vision proteins and protein receptors on host. Animal viruses do not have tails or tail fibers. have glycoprotein spikes or other attachment molecules that

What are the 3 methods of culturing viruses?

1. In mature organisms- in bacteria or in plants and animals 2. In embryonated chicken eggs- inexpensive, among the largest of cells, free of contaminating microbes and containing a nourishing yolk. 3. In cell (tissue) culture

What diseases are associated with prions?

1. fatal neurological degeneration, fibril deposits in brain and lost off brain matter. 2. large vacuoles form in brain- characteristics spongy appearance 3. spongiform encephalopathies Prions can only be destroyed by incineration

What is a capsid?

A capsid is a protein coat surrounding the nucleic acid.

what is lysogeny?

A modified replication cycle. The infected host cells grow and reproduce normally for generations before they lyse. Temperate phages- prophages- inactive phages. lysogenic conversion results when phages carry genes that alter phenotype of a bacterium.

What is a phage?

A virus that infects bacteria

Describe the replication process for an animal virus?

Attachment- Chemical attraction and exact fit between virion proteins and protein receptors on host. Animal viruses do not have tails or tail fibers. They have glycoprotein spikes or other attachment molecules that mediate attachment. Entry/uncoating- Direct penetration: capsid attaches, sinks into membranes creating a pore so genome can enter. Membrane fusion- viral envelope and cell membrane fuse, releasing capsid into cytoplasm. and endocytosis. Synthesis- each type of animal virus requires different strategy depending on its nucleic acid. DNA viruses often enter nucleus. RNA often replicates in cytoplasm must consider how mRNA is synthesized and what serves as a template for nucleic acid replication Assembly/release- Most DNA viruses assemble in nucleus and most RNA virus develops sole in cytoplasm. number of viruses produced depends on type, size, and of virus initial health of host cell. enveloped viruses cause persistent infection. host cell isn't quickly lysed. naked viruses are released by exocytosis or lysis. latency- When animal viruses remain dormant in host cells. may be prolonged for years with no viral activity. Some latent viruses do not become incorporated into host chromosomes. incorporation of provirus into host DNA is permanent

What are the five stages of the lytic replication cycle?

Attachment- depends on chemical attraction and precise fit between attachment proteins on phage and receptor proteins on surface of host cell. Entry- enzyme in capsid weakens PG of host cell wall. To be inserted into a host a genome is injected. Synthesis- viral enzymes degrade bacterial DNA and bacteria starts making new viruses. Assembly- capsomeres spontaneous attach and form capsids pr enzymes pump genome into capsids Release- newly assembled visions released as enzyme causes bacteria to disintegrate.

Whats a viroid

Extremely small, circular pieces of RNA that are infectious and pathogenic to plants. similar to RNA viruses but lack capsid

How does a virus end up with an envelope?

Its acquired from host cell during viral replication or release. the envelope is portion of the membrane system of the host. It is composed of phospholipid bilayer and proteins.- some are virally coded glycoproteins. envelopes proteins and glycoproteins often play a role in host recognition

Where are DNA and RNA viruses replicated in animal virus.

Most DNA viruses assemble in nucleus and most RNA virus develops sole in cytoplasm. number of viruses produced depends on type, size, and of virus initial health of host cell.

List the specific viruses associated with human cancers?

Specific viruses are known to cause ~15% of human cancers. ex) Burkitt's Lymphoma, Hodgkins disease, Kaposi's sarcoma (AIDs patients), Cervical cancer.

What are generalists?

They infect many kinds of cells in many different host. Ex) west nile.

What happens during latency in animal virus.

When dormant in host cells. may be prolonged for years with no viral activity. Some latent viruses do not become incorporated into host chromosomes. incorporation of provirus into host DNA is permanent

What are capsomeres?

a composed protein subunit of a capsid. They may be made of single or multiple types of proteins.

What is a virus and its characteristics?

a minuscule, acellular, infectious agent having either DNA or RNA (never both). Causes many infections in humans, plants and bacteria and most of the diseases that plague the industrialized world. It cannot carry out any metabolic pathways. neither grow or respond to the environment. can't produce independently . It recruits the hosts metabolic pathways to increase their numbers. Has no cytoplasmic membrane, cytosol, or organelles.

What is a prion?

a proteinaceous infectious agent. -cellular PrP protein made by all mammals and normal structure with alpha helices called cellular PrP. Prion PrP protein a disease causing form with beta sheets called prion PrP. Prion PrP converts to cellular PrP into Prion PrP by inducing conformational change.

What is a virus called in its extracellular state?

a virion

What are the 3 main shapes of a virus?

helical, polyhedral (spherical), and complex

How does the virus exist in the intracellular state?

in the intracellular state the virus exists as nucleic acid and the capsid is removed.

Describe hosts of a virus

most viruses infect only particular host cells due to affinity of viral surface proteins for complementary proteins on host cell. May be so specific that they only infect particular kind of cell in a particular host. Like HIV and Helper T Cells.

What is lytic replication?

replication usually results in death and sis oh host cell.

What is the primary way scientists categorize and classify viruses?

viruses show more variety in the nature of their genomes than do cells. Scientists uses DNA or RNA but never both.