OCN 621 BIOLOGICAL OCEANOGRAPHY SPRING 2011
Introduction to Viruses
Grieg Steward University of Hawaii Department of Oceanography
Friday, February 25, 2011 WHAT ARE VIRUSES?
What are they made of?
How do they replicate?
Are they alive?
Friday, February 25, 2011 Prokaryote Eukaryote
Cellular Life
Friday, February 25, 2011 Some examples of genes every cell needs and can be used to determine phylogenetic relationships DNA polymerase
RNA polymerase
Ribosomes
But there are others (e.g. those needed for energy metabolism like cytochrome C)
Friday, February 25, 2011 Tree of Life
Eukaryota
Where are the viruses?
Based on small subunit rRNA data
Friday, February 25, 2011 Replication of Cells vs Viruses
Cells: binary fission (or budding)
Viruses: parasitic replication within cells
Friday, February 25, 2011 What are viruses?
• Infectious agents that can replicate only inside a host cell • Relatively simple: • A set of instructions (DNA or RNA) • A protective coat • No motility • No metabolism
Bacteriophage Epsilon 15
Friday, February 25, 2011 BALTIMORE CLASSIFICATION
Group I: Double-stranded DNA viruses ALL other life Group II: single-stranded DNA viruses Group III: double-stranded RNA viruses Group IV: positive-sense single-stranded RNA viruses Group V: negative-sense single-stranded RNA viruses Group VI: positive-sense single-stranded RNA viruses that replicate through a DNA intermediate (retroviruses) Group VII: Double-stranded DNA viruses with ssRNA intermediates
Friday, February 25, 2011 Morphologies
Icosahedral Symmetry Bacteriophage T4
Other http://en.wikipedia.org/wiki/T4_phage HIV Filamentous Tobacco Mosaic Virus
Friday, February 25, 2011 Many shapes and Sizes
Influenza (Humans, birds, Siphovirus pig, seals) (bacteria)
Tobamovirus Calicivirus (Tobacco plant) (vertebrates)
Friday, February 25, 2011 VIRUS MORPHOLOGIES: PROKARYOTES AND PROTISTS
MURPHY, F. A. et al. , eds. (1995). Virus taxonomy. 586 p. Springer-Verlag, Wien, New York.
Friday, February 25, 2011 VIRUS MORPHOLOGIES: ANIMALS
ACKERMANN, H.-W. & BERTHIAUME, L. (1995). Atlas of Virus Diagrams. CRC Press, Inc., Boca Raton.
Friday, February 25, 2011 STEPS OF VIRAL INFECTION
Entry (of virion or its nucleic acid)
Protein synthesis
Nucleic acid replication
Assembly
Exit
Friday, February 25, 2011 MECHANISMS OF VIRUS ENTRY
Friday, February 25, 2011 Phage T4 animation
Animation: Seyet LLC (Meador, Gooding & Bartek) for Purdue University (Rossman, Leiman et al.) Friday, February 25, 2011 Viruses Infect All Types of Marine Life
•Marine mammals •Sea Birds •Fish
•Crustaceans yoto98.noaa.gov •Bivalves •Protozoa •Macroalgae (kelp) ideo.columbia.edu •Microalgae (phytoplankton) •Bacteria
en.wikipedia.org/wiki/Bacterium Friday, February 25, 2011 Viruses are Relatively Host Specific
• Many viruses infect only one species or even only one strain within a species
• Some viruses have broad host range (e.g., influenza)
• Occasionally, viruses can mutate and “jump” hosts (e.g., HIV, Ebola, Phocine/Canine Distemper)
Friday, February 25, 2011 Infection can be ugly or lethal
TURTLE HERPESVIRUS INFECTION
Turtle photos source unknown BACTERIOPHAGE INFECTION
Photos G. Steward
Friday, February 25, 2011 A VIRUS IS A PIECE OF BAD NEWS WRAPPED IN PROTEIN
SIr Peter Medawar (1915-1987)
Friday, February 25, 2011 INFECTION CAN BE BEAUTIFUL
Vase of Flowers (detail) –Jan van Huysum 1722
Friday, February 25, 2011 Can viruses make us human?
essay by L.P. Villareal (2004) Proc. Am. Phil. Soc.
Apparently Yes!
Image by Jane Ades, NHGRI
Friday, February 25, 2011 Consequences of of Infection
1. Lysis 3. Lysogenic Conversion 2. Transduction Infection Immunity
New Enzymes Toxin Production
Estimate: 43% of marine isolates harbor prophages
Friday, February 25, 2011 Phage-encoded Toxins Bacterium Phage Disease Vibrio cholerae CTXØ Cholera Hemorrhagic Escherichia coli Lambda Diarrhea
Clostridium botulinum clostridial phages Botulism
Corynebacterium diptheriae corynephage Diptheria
Streptococcus pyogenes T12 Scarlet Fever
Skin & Tissue Staphylococcus aureus various Infections ...and many more!
Friday, February 25, 2011 Where Are the Viruses?
Eukaryota
Virus
Friday, February 25, 2011 To Understand the ecology of the plankton Need to Understand the viruses with which they interact
Friday, February 25, 2011