Microbio Exam 2

characteristics of viruses:

• ACELLULAR pathogens

• visualized with ELECTRON microscope

• DNA or RNA (not both) in protein coat

what is a capsid?

• protein coat

• surrounds the genome

• protects and transports the genome to other cells

properties of viruses:

• can NOT replicate or do anything on their own

• NEED a host cell to replicate

• cannot be grown in pure culture

classification:

• eukaryotic or prokaryotic

  • based on if they infect prokaryotes or eukaryotes

• phage - infect bacteria

phage:

• vehicle for horizontal gene transfer

  • a way for bacteria to acquire new properties & virulence

• ecological significance

  • microbiome

• medical significance:

  • “phage therapy”

what is host range? (classification)

• what cell or species a virus can infect

• very LIMITED

transmission: (classification)

• indirect (like a cough)

• direct (through fluids

• vectors - insects, animals

what are capsomeres? (viral structure)**

• subunits that form a capsid

• shape of the capsid = shape of the virus

what is a nucleocapsid? (viral structure)**

• nucleic acid + capsid

what are enveloped viruses? (viral structure)**

• pick up a patch/portion of the membrane as it leaves the host cell

what are non-enveloped viruses? (viral structure)**

• naked viruses

• more resistant to disinfectants

what are spikes? (viral structure)**

• spikes are from the area of the cell the virus leaves from (spikes attach to the virus)

• protein structures

polyhedral/icosahedral (virus shapes)

• 20 flat triangles

helical (virus shapes)

• capsomeres arranged in helix

complex (virus shapes)

• phage (sheath, tail pins, and fibers

• icosahedral nucleocapsid (head) and helical protein (tail)

viral genome:

• genomes are small

• they are needed to code for

  • protein coat

  • replication

  • transportation in & out of cell

what is a big difference between bacteria and virus?

• their genome

• anything goes for viral genome

  • DNA or RNA

  • single stranded or double stranded

  • segmented or single molecule

viral replication cycle

• replication takes place in host cell

• in bacterial cells, bacteriophage replicates in cytoplasm of bacteria

budding:

• process that most enveloped viruses use to exit host cell

virulent phage

• leads to death of the host cell

• lyse cells

temperate phage

• become part of host chromosome

• progeny virus result when induced to make new viruses

lytic phage replication

• attachment

  • phage bind specific receptors on the bacterial cell

• entry

  • only the DNA is injected into the cell

• biosynthesis

  • new viral components are made

• maturation

  • assembly of a phage components

• cell lysis

  • cell is destroyed

when temperate phage infects bacterial cells, what happens?

• lysogenic cycle

  • phage DNA can integrate into the host’s DNA (DNA becomes a “prophage”)

  • occurs in slower growing, nutrient deprived cells

• lytic cycle

  • actively growing cells

lysogenic conversion

• when the properties of a bacterial cell are changed due to the bacterium carrying a phage

prophage

• the from of a phage whose DNA has been integrated into the host’s DNA

lysogen

• when a bacterial cell is carrying a prophage in its genome

what is the role of a phage in lysogenic, prophage, and lysogen conversion?

• provides extra genes to the bacteria

  • makes the bacteria more virulent

  • ex. vibrio cholerae, clostridium

transduction

• transferring DNA from one bacteria cell to another

• bacteria acquire new traits

viral replication in animal cells

• attachment

  • virus binds to receptor cites on host cell

• virus enters target cell

  • ENTIRE virus enters host cell unlike bacteriophage

    • endocytosis

• virus is uncoated; genome released

• biosynthesis of viral nucleic acids & proteins

• assembly and maturation

• release from host cell

replication of influenza virus steps

apoptosis

• non-enveloped viruses released when host cell dies

measles virus:

• infects alveolar macrophages & dendritic cells in lungs

• infects newborns (can’t get vaccines until 12 months)

• highly infectious

• many complications

• symptoms: high fever, sore throat, conjunctivitis

zoonosis

• transmissible from animals to humans

• bats, raccoons

prions

• infectious proteins

• hard to diagnose & treat