Exploring the Lytic and Lysogenic Life Cycles of Bacteriophages

Abstract

The goal of this lesson is to introduce students to the lytic and lysogenic cycles of T4 and lambda bacteriophages, respectively, using student-centered pedagogies. Bacteriophages are viruses that infect bacteria and are either virulent or temperate; virulent phages can only undergo the lytic cycle, which results in death of the host cell, while temperate phages can undergo either the lytic or lysogenic cycle, the latter of which results in the long-term association between host and virus. Bacteriophages significantly affect bacterial population in nature and are even attractive therapeutic interventions for some bacterial infections in humans. Therefore, this lesson was designed to educate students about the structure and function of bacteriophages and how viral infections can impact bacterial populations. The learning goals of this lesson are to understand how the lytic and lysogenic cycles of bacteriophages vary, affect bacterial growth, and are dictated by their unique genomes. To this end, the lesson incorporates a homework assignment for students before class, a series of in-class activities and critical thinking scenarios, and a homework assignment after class. This lesson was successfully employed in an upper-level undergraduate virology course for biology majors. Students were enthusiastic and expressed thoughtful and educated ideas during class discussion and through answers to open-ended questions. Taken together, this lesson provides an interactive and student-centered approach to studying the form and function of bacteriophages, the most abundant organisms in the biosphere. Primary image: Bacteriophage invasion: Image portrays a bacteriophage infecting a host bacterium as the first step of its replication cycle.