Bacterial Quorum Sensing and Bioluminescence

Abstract:: The bacterium Vibrio fischeri produces light when it is growing symbiotically in the light organ of certain fish and squid species. The bacteria sense they are in a light organ because they are present at a high bacterial cell density, which they detect through "quorum sensing." We use several bacterial strains, each of which carry only part of the genes responsible for the quorum sensing and bioluminescence process. We use chemical and genetic complementation to determine which genes are lacking in each strain by measuring their ability to produce and/or detect a quorum-sensing signal.

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Bacterial Virus T4: A Simple Biological System to Introduce Genetic Mapping in a Biology Laboratory Course

Abstract:: Used in conjunction with lecture material to illustrate genetic mapping.

Abstract:: Enzymes, nature's catalysts, are remarkable biomolecules capable of extraordinary specificity and selectivity. Directed evolution has been used to produce enzymes with many unique properties, including altered substrate specificity, thermal stability, organic solvent resistance, and enantioselectivity--selectivity of one stereoisomer over another. The technique of directed evolution comprises two essential steps: mutagenesis of the gene encoding the enzyme to produce a library of variants, and selection of a particular variant based on its desirable catalytic properties. In this course we will examine what kinds of enzymes are worth evolving and the strategies used for library generation and enzyme selection. We will focus on those enzymes that are used in the synthesis of drugs and in biotechnological applications. This course is one of many Advanced Undergraduate Seminars offered by the Biology Department at MIT. These seminars are tailored for students with an interest in using primary research literature to discuss and learn about current biological research in a highly interactive setting. Many instructors of the Advanced Undergraduate Seminars are postdoctoral scientists with a strong interest in teaching.

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Abstract:: This exercise presents the concepts of immunology from biochemical, evolutionary, and adaptive standpoints. While all organisms have developed some mechanism of defense against external agents, vertebrates have the most complex immune responses capable of exquisite specificity and long duration. This affords a distinct advantage to species with a relatively long life span and low fecundity. This exercise explores the relationship between immunologic stimulation of the host with foreign antigens and antibody production. The principles of species specificity, primary and secondary immune responses, cross-reactivity, and complement-mediated cell lysis are demonstrated using the red cell agglutination assay. Agglutination occurs when a single antibody molecule binds simultaneously to a surface antigen on two red cells a principle used daily in the diagnosis of viral infections and blood groups incompatibility in humans and other animals.