Viruses Flashcards
(20 cards)
What are the most abundant biological entities in the ocean?
Viruses!
How many viral infections occur every second?
~10^23
What is the most common host for viruses?
- Bacteria = most abundant
- Phytoplankton
- Zooplankton
Viruses are ___ and ___ specific
Species and Strain
Are viruses DNA or RNA based?
Can be either
Are viruses considered living?
- No
- They cannot reproduce without a host
What are the 3 major reproductive cyles for viruses?
- Lytic
- Lysogenic
- Productive infection / budding
Describe a lytic virus
- Attachment
- Penetration/injection
- Synthesis of nucleic acids/proteins
- Assembly and packaging
- Release (lysis)
Lysis will always kill the host
What is one way that an organism can mask itself from a virus?
- Block external protein receptors!
- Without receptors the virus cannot recognize the host
Describe a lysogenic virus
- Attachment
2 options:
1. Lytic pathway
2. Lysogenic pathway - Viral DNA is integrated into host DNA
- Cell Division and normal cell growth commences
Virus may stay lysogenic under poor environmental conditions and switch to lytic when conditions = favorable
Describe viral budding
- Host is infected BUT will not die
- Host will continue to produce new viruses
What technique has been used to quantify viruses?
Epifluorescence with DNA stains
What is horizontal gene transfer?
Transfer of genetic material between unrelated individuals
What is vertical gene transfer?
Transfer of genetic material between parent and offspring
What are methods f horizontal gene transfer?
- Transformation: intro/uptake of ew genetic info.
- Transduction: mispacking
- Bacterial conjugation: cell-cell contact
- Gene transfer agents: virus-like elements = encoded into the host
Describe mispacking
When lysing a cell the virus will accidentally pack some of the hosts DNA into its genome and then inject the host’s DNA into another host
This drives evolution
How can viruses impact diversity
Resistance to viruses shapes microbial diversity
How can viruses enhance microbial growth rates?
They can produce labile organic matter
BUT this will overall decrease food chain productivity as viruses will catalyze the movement of nutrients from organisms to the DOM nd POM pools
How do viruses affect the biological pump?
Viruses will break down plankton into DOM and POM allowing components to remain in photic zone (no sinking)
What can some phytoplankton do to protect themselves against viral exposure?
- Cheshire cat hypothesis
- Plankton can change their life stage to one that is resistant to viruses
