Bacteria and Bacteria and VirusesVirusesChapter 18Chapter 18

E. ColiE. Coli

What is a Virus?What is a Virus?NonlivingNonliving particleparticle—Why not —Why not alive?alive?No respirationNo respirationDoesn’t grow or Doesn’t grow or developdevelopNeed a host to replicateNeed a host to replicate

Composed of Composed of nucleic acidsnucleic acids in in protein coatprotein coat

Very small—smaller than Very small—smaller than bacteriabacteria

NamingNamingOften named after the Often named after the diseasedisease they cause they cause (poliovirus, rabies virus)(poliovirus, rabies virus)

Sometimes named after Sometimes named after the tissue they are found the tissue they are found in (adenovirus [causes in (adenovirus [causes common cold] found in common cold] found in adenoid adenoid tissuetissue))

Code numbers used to Code numbers used to distinguish between distinguish between similar viruses that infect similar viruses that infect the same host (ex. T1-T7 the same host (ex. T1-T7 for viruses that infect for viruses that infect E. E. colicoli

Viruses that infect Viruses that infect bacteriabacteria are called are called bacteriophages or phagesbacteriophages or phages

StructureStructureInner core of nucleic acid—Inner core of nucleic acid—can be can be DNA or RNADNA or RNA

Outer coat= Outer coat= CapsidCapsid. The . The proteins found within the proteins found within the capsid determine shape. capsid determine shape. This also determines how This also determines how the virus infects the cell and the virus infects the cell and what cells can be infected.what cells can be infected.

EnvelopeEnvelope—additional —additional layer outside capsid layer outside capsid that some larger that some larger viruses have (like viruses have (like human flu virus).human flu virus).Similar to Similar to plasma plasma membranemembrane

AttachmentAttachment Virus protein Virus protein interlocksinterlocks with a with a receptor site on host’s plasma receptor site on host’s plasma membrane—similar to 2 puzzle membrane—similar to 2 puzzle pieces attachingpieces attaching

Virus attachment proteins are Virus attachment proteins are specific to each specific to each virusvirus—each virus —each virus can only attach to a few kinds of can only attach to a few kinds of cells (ex. T4 phage can only cells (ex. T4 phage can only attach to attach to E. coliE. coli and not any and not any other bacteria, human, plant)other bacteria, human, plant)

Replication CyclesReplication Cycles There are two types: There are two types:

The The LyticLytic Cycle Cycle The The LysogenicLysogenic Cycle Cycle

Viruses that replicate by the lytic Viruses that replicate by the lytic cycle:cycle:Have Have shortshort incubation times incubation timesDo not reoccur Do not reoccur Take about 30 mins to make Take about 30 mins to make 200 200 viruses viruses

The Lytic CycleThe Lytic Cycle

The Lysogenic CycleThe Lysogenic CycleViruses that replicate Viruses that replicate by the lysogenic cycle:by the lysogenic cycle:Have Have longlong incubation incubation times times

Reoccur on a Reoccur on a regularregular basisbasis

Form a Form a provirusprovirus

The Lysogenic CycleThe Lysogenic CycleProvirus Provirus Viral DNAViral DNA that that is integrated into the is integrated into the host cell’s chromosome host cell’s chromosome May not effect May not effect hosthost cell’s functioning cell’s functioning

Reproduces as the host Reproduces as the host cell cell reproducesreproduces

Bacteria Bacteria TinyTiny (about 1/1000 (about 1/1000thth of a of a mm) mm)

Found everywhere, on your Found everywhere, on your skin, in the air, on the skin, in the air, on the tables, most tables, most anywhereanywhere you you can think of, there are can think of, there are bacteria. bacteria.

Can both hurt and help Can both hurt and help humanshumans

Bacteria are Bacteria are prokaryotesprokaryotes

Prokaryotes – No Prokaryotes – No nucleusnucleus, , No membrane bound No membrane bound organelles (no organelles (no chloroplasts, mitochondria, chloroplasts, mitochondria, or vacuoles); organisms are or vacuoles); organisms are singlesingle celled celled

Eukaryotes – Nucleated, Eukaryotes – Nucleated, membrane bound membrane bound organelles, can be organelles, can be multicellular or unicellular.multicellular or unicellular.

2 types 2 types Archea – Archea – extremeextreme bacteria. bacteria. Live in high salt, high Live in high salt, high temp, high pressure temp, high pressure environments, usually environments, usually found in anoxic conditions found in anoxic conditions

Eubacteria – “true” Eubacteria – “true” bacteria. Live in more bacteria. Live in more moderatemoderate conditions conditions (usually in oxygen)(usually in oxygen)

Bacterial Cell StructureBacterial Cell StructureCapsuleCapsule – sticky outer – sticky outer covering that protects against covering that protects against phagocytosis, toxins and viral phagocytosis, toxins and viral infection infection

Endospore – tough barrier that Endospore – tough barrier that protectsprotects the bacterial the bacterial chromosome from dehydration chromosome from dehydration when environment lacks when environment lacks water.water.

Cell Wall – Provides Cell Wall – Provides structure, support, & structure, support, & protects against cell protects against cell lysislysis

Flagella – Flagella – WhipWhip like like structure that spins to structure that spins to allow bacteria to moveallow bacteria to move

Pili – Smaller hair like Pili – Smaller hair like projections on the projections on the surfacesurface of of bacteria that allow it to stick bacteria that allow it to stick to a surface. to a surface.

Plasmid – small segment of Plasmid – small segment of genetic materialgenetic material (contains (contains extra genes)extra genes)

Bacterial Reproduction: Bacterial Reproduction: Reproduce Reproduce asexuallyasexually - - They don’t need genetic They don’t need genetic material of other bacteria material of other bacteria (no gametes)(no gametes)Binary Fission – similar Binary Fission – similar to to mitosismitosis, chromosome , chromosome doubles, and then is split doubles, and then is split between the two cells.between the two cells.