Increasing student interest with the Bacterial Unknown Identification Project: using mixed cultures to create real-world applications.

Many introductory-level classes teach fundamental concepts, as they are prerequisites for upper-division courses. Therefore, the student body in these classes has diverse interests. To address this breadth of career trajectory, introductory-level laboratory courses often include experiments that demonstrate a wide range of microbiological techniques and processes. One of the experiments that is a standard component of many microbiology classes, the Bacterial Unknown Identification Project (BUIP), is often limited to isolated organisms or a specific environment. Here, we describe an updated method for the BUIP that incorporates the projected student career diversity through the implementation of multiple mixed cultures of microorganisms associated with different environments. This update can be utilized in any microbiology laboratory classroom. We maintained the learning objectives, including applying appropriate microbiological methods to analyze and interpret results, and effectively communicate scientific findings, while modifying the sample composition. Assessment of the modification demonstrated that upon completion of the BUIP, students felt that the project applied to their career and it did not take too much of their free time to complete.

The metaeffector MesI regulates the activity of the Legionella effector SidI through direct protein-protein interactions.

To create an intracellular niche permissive for its replication, Legionella pneumophila uses hundreds of effectors to target a wide variety of host proteins and manipulate specific host processes such as immune response, and vesicle trafficking. To avoid unwanted disruption of host physiology, this pathogen also imposes precise control of its virulence by the use of effectors called metaeffectors to regulate the activity of other effectors. A number of effector/metaeffector pairs with distinct regulatory mechanisms have been characterized, including abrogation of protein modifications, direct modification of the effector and direct binding to the catalytic pocket of the cognate effector. Recently, MesI (Lpg2505) was found to be a metaeffector of SidI, an effector involved in inhibiting host protein translation. Here we demonstrate that MesI functions by inhibiting the activity of SidI via direct protein-protein interactions. We show that this interaction occurs within L. pneumophila and thus interferes with the translocation of SidI into host cells. We also solved the structure of MesI, which suggests that this protein does not have an active site similar to any known enzymes. Analysis of deletion mutants allowed the identification of regions within SidI and MesI that are important for their interactions.