Transcript Slide 1

IMAGING THE MARINE BACTERIUM Trichodesmium erythraeum
BY ATOMIC FORCE MICROSCOPY
Arthur J. Gutzler, Simara Price, Dr. Shivanthi Anandan, Dr. Bradley E. Layton
Research Experience For Teachers
Father Judge High School
The Cell and Protein Mechanics Laboratory, Department of Mechanical Engineering and Mechanics
Drexel University, PA, 19104
Objective
To obtain high resolution images of the marine
bacterium Trichodesmium erythraeum.
Results
Project Overview
•Obtain sample of T. erythraeum
•Prepare slides for imaging by an atomic force microscope (AFM)
possible
collagen fibril
•Analyze the images using AFM software
Background/Motivation
•Construct a 3-D model using rapid prototyping technology
Atomic Force Microscopy Images
The marine colonial bacterium Trichodesmium
erythraeum contributes more oceanic nitrogen
than any other cyanobacteria and so plays a
major role in the fixation of nitrogen for use by
other forms of marine life(1). The bacteria is
capable of forming colonies that may cover
many square kilometers of ocean surface. It is
known that T. erythraeum contains a gene for
collagen but the role of collagen remains
unknown(2). Collagen fibrils may make these
extensive oceanic bacterial mats possible. By
studying detailed images of bacterial samples
we hope to determine how and when the gene
is expressed and if collagen plays a role in
maintaining the mechanical integrity of the
colony.
Atomic force microscopy is well suited to image
the surface features of cells. Its nanometer
range tip performs a raster scan of the surface
of a sample, in this case a colony of T.
erythraeum. The processing software is
capable of producing the images that are shown
in this poster.
References
(1) Capone DG, Zehr JP, Paerl HW, Bergman P, Carpenter EJ (1997), Trichodesmium, a
globally significant marine cyanobacterium. Science 276:1221-1229
(2) Layton BE, D’Souza AJ, Dampier W, Ziegler A, Sabur A, Jean-Charles J (2008), J Mol Evol
DOI 10.1007/s00239-008-9111-7
Images were scanned with a Veeco Dimension 3100
Nanoscope at a 1 Hz rate using 512 lines per image.
This AFM image shows that it is
relatively easy to distinguish a
separation between rows of cells
but it is more of a challenge to
determine boundaries between
individual cells. The arrows indicate
the location of two cells with a
boundary between them.
possible
banding
3-D model of a
colony of T.
erythraeum.
produced using
rapid
prototyping
A cell count was established using
the view to the left. Arrows indicate
that the cells could be divided into
19 approximately parallel tracks.
Using the measured cell width of 5
µm and measuring the length of
visible cells in each track, a count
of 176 cells was established.
Conclusions & Future Work
To prepare the above sample, 2.5 µL was pipetted onto a mica
disk. With a count of 176 cells in the sample, this would equate
to a cell count of 7.0 x 107 cells/L
The arrow in the image to the
left indicates a possible collagen
fibril. The image was produced
from the first sea water sample
of T. erythraeum. Further
imaging showed that additional
rinsing of the sample can
minimize the presence of salt
crystals which can be seen.
• Create a laboratory colony of T. erythraeum that
can be examined for the presence of collagen.
• Modify bacteria to turn off the collagen gene and
determine the effect on T. erythraeum’s ability to
form bacterial mats
Acknowledgements
Andrew Bohl and Richard Primerano for making the
3-D image printing possible. This work was
sponsored by NSF Grant CMMI 0900101