Isolation of Viruses Collected from the South Shore Waters of Oahu

Sarah ChangAdvisors:

Alexander CulleyGrieg Steward

Outline• Introduction

– What is a Virus?– What is a Diatom?– Objective

• Materials and methods• Data/results• Conclusions• Acknowledgements

What is a Virus?

• Microscopic particles of genetic material, surrounded by a protein coat

• Incapable of autonomous reproduction

• Three types of viral reproduction– Lytic, Lysogenic, Chronic

infection

Virology.net

Suttle

Viruses in the Ocean

• Marine viruses are abundant (billions per liter)

•• Infect a diversity of marine life.

ideo.columbia.edu yoto98.noaa.gov

Culley

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

Waimanalo Waimanalo BayBay

Kaneohe BayKaneohe Bay

MaunaluaMaunaluaBayBay

Kuapa PondKuapa Pond

Waialae Waialae Beach ParkBeach Park

Waikiki Beach Waikiki Beach ParkPark

Wailupe Wailupe Beach ParkBeach Park

forum.hardware.fr

• 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:– Exponential growth

in Control tubes– Exponential growth

in Treated tubes, followed by severe decline

But as the great Mick Jagger said…

Ideal Growth Curve

0

20

40

60

80

100

120

140

1 3 5 7 9 11 13

Days

RF

U C C-L

T C-L

Fluorescence measurements showed consistent growth in Treated tubes and decline in the Control.

Growth Curves for Culture L (10/10 - 11/14)

0

100

200

300

400

500

600

1 3 5 7 9 11 13 15

Days

RF

U C C-L

T C-L

Data/Results

Little growth in control and treated cultures

Growth Curves for Culture R

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8

Days

RFU C C-R

T C-R

Growth Curves for Culture C

0

20

40

60

80

100

120

1 3 5 7 9 11

Days

RFU C C-C

T C-C

11/3/08

Growth curves for culture N

020406080

100120140

1 2 3 4 5 6 7 8

Days

RFU

C C-NT C-N

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 screening4. 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!