Chapter5B: Bacteriophage & AcellularInfectiousAgents

Bacteriophage

“Bacteria eating” type of virus that infects and replicates within bacteria every bacterial species is parasitism’s by various bacteriophages have head structure(capsid) and a tail

Capsid

The “head structure” protein shell of a virus that encases its genetic material.

Capsomeres

Capsid contains constructed from identical protein subunits they have viral genomes DNA or RNA

Tail

Mediates attachment, digestions and penetration of bacterial cell envelope allows phage in inject their genome into host cells and establish infection

Two main types of bacteriophage

Virulent phage, temperate phage

Virulent(lyric) phage

One reproductive choice multiples Immediately upon entering a bacterial host, released from host by lysis

Temperate(lysogenic) phage

Two reproductive options reproduce lyrically as virulent phage do remain within host cell without destroying it

Beginning of life cycle of phage

Phage must first come into contact with bacterial cell encoding a receptor

Second part of life cycle of phage

Cell contact will be established, phage nucleic acids enter the bacterial cell and bag in to either replicate(lytic cycle), or establish state of silence(lysogenic cycle)

Lysogenic viruses

Are also known as temperate phages

Temperate phages cycle

Undergo adsorption and penetration do not do replication and release immediately

Propane state

Phage DNA enters an inactive state inserted into bacterial chromosome, copied during normal bacterial cell division

Lysogeny

A condition in which the host chromosomes carries bacteriophage DNA

Lysogenic bacteria

Infected bacteria immunity to that virus, cannot be reinfected

Lysogenic cycle

Phages can switch to the lytic cycle by a process called induction

Induction

Prophage in a lysogenic cell becomes activated and progresses directly into viral replication and lytic cycle

Lysogenic phage can be induced

Spontaneously, by signals in their environment (nutrients,toxic chemicals) by signals within the cell senescence, injury

Role of lysogeny in human disease

Occasionally,phage genes in bacterial chromosomes caused the production of toxins or enzymes that the bacterium would not otherwise have

Lysogenic conversion

When a bacterium acquires a new trait from its temperature phage

Culturing viruses

Viruses require living cells as their medium, in vivo and in vitro

In vivo

Laboratory bred animals and embryonic bird tissues

In vitro

Cell or tissue culture methods

In vivo culturing

Mice,rats,hamsters,Guinea pigs, and rabbits are the usual choices for viral cultivation; bird eggs containing embryos fertilized egg

In vitro virus culturing

Isolated animal cell re grown in vitro in cell tissue culture rather than animal or egg

Cell culture, or tissue culture

Grown in sterile chambers with special media that contains the correct nutrients for cells to survive ,cells from monolayer or single confluent sheet of cells that support viral multiplication

Detection of viral growth in cultures

Observations of degeneration and lysis of infected cells

Plaques

Areas where virus infected cells have been destroyed shown up as clear well defined patches in cell sheet, visible manifestation of cytopathic effects(CPEs) and cell lysis

Plaque essay technique

Is also used to detect and count bacteriophages

When do plaques together

When viruses released by an infected host cell radiates out to adjacent host cells, new cells become infected fiend releases more viruses and the process continues

How plaque manifest

As macroscopic,round,clear space that corresponds to areas of dead cells

Prions

Composed primarily of protein (nucleic acid), causes a variety of neurodegenerative diseases in humans and animals

Prions deposited

As long protein fibrils in the brain tissue of humans and animals, resulting in brain atrophy(wasting)

Burst size

The number of phage released from a single infected bacterial cell.

Lytic cycle

The process by which virulent phages multiply and cause lysis of the host cell.

Lysogenic cycle

The process by which temperate phages integrate their genome into the host's chromosome without killing the host.

Prophage

The inactive form of a phage genome integrated into a bacterial chromosome.

Lysogenic conversion

The process by which bacteria acquire new traits from a lysogenic phage.

Induction

The process by which a prophage is activated to enter the lytic cycle.

Satellite viruses

Viruses that depend on other viruses for replication.

Adeno associated virus (AAV)

Originally thought that it could only replicate in cells infected with the adenovirus, can also infect cells that are infected with other viruses

Delta agent(hepatitis delta virus HDV)

Naked circle of RNA, expressed only in the presence of hepatitis B virus,worsens the severity of liver damage

Viroids

Virus like agents that parasitize plants composed of naked strands of RNA lacking a capsid or any other type of coating

Viroids size

About one tenth the size of an average virus

Temperate phage

A type of bacteriophage that can enter a lysogenic cycle.

Virulent phage

A type of bacteriophage that reproduces by the lytic cycle.

Bacteria

Single-celled microorganisms that can exist in various environments.

Eukaryote

An organism made up of cells with a nucleus enclosed within membranes.

Prokaryote

A single-celled organism that lacks a nucleus and other membrane-bound organelles.

Antibiotics

Medicines that inhibit bacterial growth or kill bacteria.

Virus

A small infectious agent that replicates only inside the living cells of an organism.

Pathogen

An organism that causes disease in its host.

Spores

A reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions.

Microbiome

The collection of microbes in a specific environment, such as the human gut.

Genetic recombination

The process by which genetic material is physically mixed to produce a new combination.

Horizontal gene transfer

The transfer of genetic material between organisms in a manner other than traditional reproduction.

Host cell

A living cell in which a virus or phage replicates.

Symbiosis

A mutually beneficial relationship between different organisms.

Infection

The invasion and multiplication of microorganisms in body tissues.