Wednesday, December 16, 2009

shape and survival

11.16.09. Microorganisms come in many shapes, from spherical and rod-shaped bacteria to egg-shaped budding yeast to mutably-shaped amoeba. Shape can be an important factor in an organism's survival; for example, it is often advantageous (on an evolutionary scale) for a microorganism to maximize its surface area (in order to increase the amount of nutrients taken in) and minimize its volume (in order to reduce the amount of nutrients needed). We studied the analog of this problem in two dimensions, measuring for various 2-D cutouts the ratio of perimeter to length (length, a proxy for area or volume, was defined as the longest straight line spanning the shape). Ratios for amoebic cross-sections were by far the largest and most variable across the population, while ratios for circles (representing cross-sections of, e.g., spherical Staphylococcus aureus bacteria) all neared the famous, irrational pi.