IMAGING THE MARINE BACTERIUM Trichodesmium erythraeumBY ATOMIC FORCE MICROSCOPY

Arthur J. Gutzler, Simara Price, Dr. Shivanthi Anandan, Dr. Bradley E. LaytonResearch Experience For Teachers

Father Judge High School

The Cell and Protein Mechanics Laboratory, Department of Mechanical Engineering and MechanicsDrexel University, PA, 19104

To obtain high resolution images of the marine bacterium Trichodesmium erythraeum.

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

Objective Project Overview Results

Background/Motivation

Atomic Force Microscopy Images

Conclusions & Future Work

Acknowledgements

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.

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.

•Obtain sample of T. erythraeum

•Prepare slides for imaging by an atomic force microscope (AFM)

•Analyze the images using AFM software

•Construct a 3-D model using rapid prototyping technology

• 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

Andrew Bohl and Richard Primerano for making the 3-D image printing possible. This work was sponsored by NSF Grant CMMI 0900101

possible collagen fibril

possible banding

Images were scanned with a Veeco Dimension 3100 Nanoscope at a 1 Hz rate using 512 lines per image.

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.

3-D model of a colony of T. erythraeum.

produced using rapid

prototyping