The Cytoarchitecture of Large Bacteria

Cornell University, Ithaca NY

Investigators

Abstract

Intellectual Merit: Using Epulopiscium as a model, one of the Angert lab's long term research goals is to address a fundamental problem faced by all large cells; how does a cell with a small surface-to-volume ratio overcome constraints imposed on it by the diffusion coefficients of bioactive molecules? With cigar-shaped cells reaching 600 µm x 80 µm, Epulopiscium spp. are the largest heterotrophic bacteria described to date. Despite its size, Epulopiscium is able to support a high level of activity. The presence of large amounts of repetitive DNA located at the periphery of the cytoplasm and a highly invaginated cell membrane may be significant adaptations to maintain large cell size in Epulopiscium. The amplification and distribution of genomic resources help support a robust metabolism while expansion of the cell membrane and membrane associate transporters may enhance exchange with the environment and facilitate movement of molecules within the cytoplasm. In this project Dr. Angert and her colleagues seek to further characterize these features and determine 1) the timing and location of DNA replication in the cell, 2) how multiple chromosomes with differing fates are positioned and managed and 3) the impact of intracellular membranes on molecular diffusion. Continued efforts toward culturing Epulopiscium spp. are planned. Maintaining Epulopiscium outside of its host will allow for in vivo experiments and ultimately the development of genetic tools. Broader Impacts: These projects provide significant educational and training opportunities for graduate, undergraduate and high school students interested in the sciences. All students will gain experience in basic molecular biology, microbiology and microscopic techniques. Depending on the project, students will gain more extensive experience in areas such as genomics, microscopy, phylogenetic analyses or nanobiotechnology, to name a few. Such laboratory research experience is essential to the development of a young scientist. Epulopiscium provides an exciting model for conveying basic concepts of the bacterial cell. These cells are visually appealing and can be seen with the unaided eye. The fact that Epulopiscium spp. are so large, but not pathogenic, makes them a good representative of the microbial world not only for biology students but for the general public as well. To facilitate information flow, a website featuring Epulopiscium has been established. Students at all levels are involved in the development and maintenance of the site. This project instills in students the responsibility of all researchers to disseminate information to the public and it will enhance the ability of the students to communicate their work and its significance to a diverse audience. In addition, members of the Angert Lab assist with a Cornell Institute for Biology Teachers Summer Workshop called The Microbial World.