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 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 10 7 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