Isolation of Viruses Collected from the
South Shore Waters of Oahu
Sarah Chang
Advisors:
Alexander Culley
Grieg Steward
Outline
• Introduction
– What is a Virus?
– What is a Diatom?
– Objective
•
•
•
•
Materials and methods
Data/results
Conclusions
Acknowledgements
What is a Virus?
Virology.net
• Microscopic particles of
genetic material,
surrounded by a protein
coat
• Incapable of autonomous
reproduction
• Three types of viral
reproduction
– Lytic, Lysogenic, Chronic
infection
Suttle
Viruses in the Ocean
Culley
• Marine viruses are
abundant (billions
per liter)
• Infect a diversity of marine life.
ideo.columbia.edu
yoto98.noaa.gov
What is a Diatom?
• Unicellular eukaryotic
phytoplankton
• Have frustules
composed of silica
• May be solitary or
chain-forming;
pennate or centric
NSF Polar Programs
Why are diatoms important???
• Lowest trophic level and act as the food source for
many higher organisms.
• Make a major contribution to global primary
productivity
• Viruses can affect the transfer of material through
the food web.
• Diatoms are used in:
–
–
–
–
Nanotechnology: Harvest silica
Insulating materials
Explosives
Filters and more.
Kroger
Diatom Viruses
• Thought for some time that diatoms might not
have viruses (protected by frustule)
• But no, they are not immune
• Just took a long time to
find the first one; only a
few diatom viruses have
been isolated so far
Nagasaki et al. 2004
Objective
To isolate viruses infecting representative
diatoms from coastal waters of Oahu that
could be useful as model systems to study
virus-diatom interactions
Materials and Methods
• 19 strains of diatoms isolated from coastal waters by Dr.
Susan Brown
• Growth of the cultures was monitored by measuring
chlorophyll fluorescence
• Nine cultures were chosen to be challenged with viruses
Kaneohe Bay
Waimanalo
Bay
Wailupe
Beach Park
Kuapa Pond
Waikiki Beach
Park
Waialae
Beach Park
forum.hardware.fr
Maunalua
Bay
• Water was filtered
through 0.22 µm
filters
• The filtrate was
transferred into tubes
of diatom cultures
(control tubes received
no addition)
• Growth was monitored
over time in treated
and control tubes
• Idealized results:
140
120
100
RFU
– Exponential growth
in Control tubes
– Exponential growth
in Treated tubes,
followed by severe
decline
Ideal Growth Curve
80
C C-L
T C-L
60
40
20
Days
13
11
9
7
5
3
0
1
But as the great Mick Jagger said…
Data/Results
Growth Curves for Culture L (10/10 - 11/14)
600
500
400
C C-L
300
T C-L
200
100
Days
15
13
11
9
7
5
3
0
1
RFU
Fluorescence
measurements
showed consistent
growth in Treated
tubes and decline in
the Control.
Growth Curves for Culture R
7
6
5
RFU
Little growth in
control and
treated cultures
4
C C-R
3
T C-R
2
1
0
1
2
3
4
5
Days
6
7
8
Grow th curves for culture N
Growth Curves for Culture C
120
140
120
100
C C-C
T C-C
60
40
RFU
RFU
80
100
80
C C-N
T C-N
60
40
20
0
20
0
1
3
5
7
9 11
1 2 3 4 5 6 7 8
Days
Days
11/3/08
11/12/08
Conclusions
• Documented the growth patterns of diatoms
• Challenged diatom cultures with viral
communities from various locations on the
island
• Found a few cultures showing inhibition in
treatment relative to the control, but no
crashes
Future Research
1. Set up the second round of infection to see
if inhibitory effect can be propagated
2. Continue experiments challenging with
additional virus sources and new cultures
of diatoms
3. Developing higher-throughput screening
4. If a virus is found, it will be isolated and
characterized
Thank you
• The National Science Foundation
• C-MORE
Thank you to my mentors Alex Culley and
Grieg Steward, and to the members of the
Steward lab.
Thanks!