Microbiology ch 13

• -Obligatory intracellular parasites 
• -Contain DNA or RNA
• -Contain a protein coat
• -Some are enclosed by an envelope
• -some viruses have spikes
• -most viruses infect only specific types of cells in one host
• -Host range is deteremined by speficif host attachement sites and cellular factors.  

• -Nucleic acid -----DNA or RNA 
• -Capsid-----Capsomeres
• -Envelope
• -Spikes

-viridae

-virus

A group of viruses sharing the same genetic information and ecological niche(host). Comon names are used for species 

Subspecies are designated by a number.  

Examples: 

• * Herpesviridae
• * Retroviridae

• *Herpesvirus
• *Lentivirus

-Human herpes virus-- HHV-1, HHV-2, HHV-3

• -Human immunodeficiency virus HIV-1, HIV2
•  

Bacteriophages form plaques on a lawn of bacteria 

Animal viruse may be grown in living animals or in embryonated eggs

continuouss cell lines may be maintained indefinitely 

• serological tests
• -detect antibodies against viruses in a patient
• -uses antibodies to identify viruses in netralization tests, viral hemagglutination, and Western blot 
•  

• -Attachment
• -Penetration
• -Biosynthesis
• -Maturation
• -Release
•  

Phage attaches by tail fibers to host cell

Phage lysozyme opens cell wall, tail sheath contracts to force tail core and DNA into cell

Production of phage DNA and proteins

Assembly of phage particles

Phage lysozyme breaks cell wall

Phages causes lysis and death of host cell

• -Prophage DNA incoporated in host DNA
• -Phage conversion
• -Specialized transduction
•  

• -Latent cells
• -possible prophage (insertion into bacterial chromosome)
• -three results of lysogeny:
•         *immune to reinfection
•         *phage conversion
•         *specialized transduction

• -Attachment: viruses attach to cell membrane
• -Penetration: by endocytosis or fusion
• -Uncoating: by viral or host enzymes
• -biosynthesis:production of nucleic acid and proteins
• -Maturation: nucleic acid and capsid proteins assemble
• -Release: by budding (enveloped viruses) or rupture 

Happens by pinocytosis

By Fusion

• -Activated oncogenes transform normal cells into cancerous cells
• -Transformed cells have increased growth, loss of contact inhibition, tumor-specific transplant antigens, and T antigens
• -The genetic material of oncogenic viruses becomes integrated into the host cell's DNA 

• -Adenoviridae
• -Herpesviridae
• -Poxviridae
• -Papovaviridae
• -Hepadnaviridae
•  

• -Retroviridae
• -Viral RNA is transcribed to DNA, which can integrate into host DNA
• -HTLV-1
• -HTLV-2 

Virus remains in asympotmatic host cell for long periods

-COld sores, shingles 

• -Disease processes occurs over a long period; generally is fatal
•     *subacute sclerosing panencephalitis (measles virus)  

A prion is a protein.

• -Proteinaceous infection particle
• -Inherited and transmissible by ingestion, transplant, and surgical instruments
•      -spongiform encephalopathies: sheep scrapie, Creutzfeldt-Jakob disease, Gerstmann-Straussler-Scheinker syndrome, fatal familial insomnia, mad cow disease

**Must come in contact with brain to be infected with any prion disease  

PrPc: Normal cellular prion protein, on cell surface

PrPsc: Scrapie protein; accumulates in brain cells, forming plaques  

Enter through wounds or via insects

Infectious RNA 

-potato spindle tuber disease

**only found to infect plants. Very specific, can only infect plants

Become plaque or build up of proteins 

• -Single-stranded RNA, 
•     -each strand, has multiple RNA strands

• -enveloped spikes can agglutinate RBCs
• -Influenzavirus (influenza viruses A and B)
• -Influenza C virus