Viruses and Monera
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Transcript of Viruses and Monera
Viruses and Monera
Microbiology – study of small life
Virus – “poison”
• Alive? – we are not sure. Consensus is they are not alive, they meet some but not all of the traits of life
Why study?
• They affect living things, also helps understand difference between life and non-life
Composition and Structure
Composition and Structure
• Nucleic acid – DNA or RNA, genetic material
Composition and Structure
• Protein coat - (capsid) surrounds and protects the nucleic acid
Composition and Structure
• Envelope – additional protective coating, contains spikes that bind to sites on a cell
Classification
Shape Host they infect
How they function
Shape – the arrangement of proteins in capsids
Helical
• RNA coils tightly inside the long, narrow capsid
Binal
• Two parts, polyhedral capsid and a helical tail
Polyhedral
• Multifaceted geometric appearance
Adenovirus is one that causes colds
Filovirus
• No distinct shape, threadlike or looped at end
What shape is it?
What shape is it?
What shape is it?
What shape is it?
Host – who they infect
Animal
• infect only animals
Plant
• Infect only plants
Bacteria
• (bacteriophages) Infect only bacteria
Other
• Can infect many different hosts or only certain species of that host
Function
• How they behave or work inside a host
Normal viruses and Retroviruses
Retrovirus
• “reverse” virus, turns its RNA to DNA
Discovery – found by surprise, looking for the cause of tobacco mosaic disease
Dmitri Ivanovsky
• Must be caused by unusually small bacteria or poisons from bacteria
Russian Biologist1892
Martinus Beijerinck
• Caused by something smaller than bacteria, an infectious agent he called virus
Dutch Biologist1897
Still unsure where viruses came from, but have discovered many diseases since that have been caused by viruses
Viral Diseases in Humans:
• Common cold
Viral Diseases in Humans:
• Measles
infection of the respiratory system, spread through air, fever, cough, red eyes, rash
Viral Diseases in Humans:
• Warts
Viral Diseases in Humans:
• AIDS
Auto immune deficiency syndrome – spread through body fluids or blood
Viral Diseases in Humans:
• Mono
Spread through saliva or mucus, fatigue, swollen lymph nodes, enlarged spleen
Viral Diseases in Humans:
• Polio
damage the nervous system and cause paralysisEnters mouth by contaminated hands with feces
Viral Diseases in Humans:
• Viral pneumonia
Inflammation of the lungs, cough with mucus, fever, chills
Viral Replication – do not reproduce,
no cell division, need a host
Host
• An organism that shelters and nourishes something
Lytic Life Cycle
• Virus rapidly kills the host cell (lyses = break apart)
Lytic Life Cycle
• Attachment – virus sticks to cell and enzymes eat a hole in host cell membrane
Lytic Life Cycle
• Entry – viral DNA enters host cell and takes control
Lytic Life Cycle
• Replication – viral DNA instructs host to make copies of itself and protein coats
Lytic Life Cycle
• Assembly – viral parts are put together to form new viruses
Lytic Life Cycle
• Release – host cell bursts releasing new viruses
Then it all starts again…
But sometimes…
Lysogenic cycle
• Virus doesn’t immediately kill the host cell
Lysogenic cycle
• Attachment – virus sticks to cell and enzymes eat a hole in host cell membrane
Lysogenic cycle
• Entry – viral DNA enters host cell and inserts into chromosomes
Lysogenic cycle
• Replication – host cell divides, replicating viral DNA with own DNA
Lysogenic cycle
• Stimulus – something causes the viral DNA to separate from chromosome and enter Lytic cycle
Without a stimulus, the viral DNA stays dormant in the cell’s chromosomes
Lysogenic cycle
• That’s how people with HIV can go years without showing symptoms of AIDS, and still pass the virus on to others
Non-viral Particles
• Recently discovered particles that act like viruses
VIROIDS PRIONS
Viroids
• Just a nucleic acid (no protein coat)
• Causes – plant diseases
Prions
• Just a protein (no nucleic acid)
• Causes – mad cows disease