Phage Biology

Bacteriophages offer an unparalleled tool for teaching microbial physiology and ecology as well as molecular biology and critical thinking to students at all levels, through class and small-group projects. It is exciting for students to come up with ideas that have not been thought of or tried before, once students learn basic techniques and theory of phage infection they can independently conduct experiments, and start thinking scientifically, on their own. Fifteen years ago, some undergrads asked; "Why does the T4 infection protocol require vigorous aeration? Don't they live in anaerobic guts?” Finding no relevant literature, they soon showed that T4 could infect well anaerobically – and all soon learned about anaerobic respiration and fermentation and thought about E. coli's physiology in its natural habitats. Those anaerobic experiments led to our using T4-like phages to clear E. coli O157 from ruminant guts. Other current student explorations include:

(1) T4 was believed not to infect stationary-phase cells. However, we have characterized 2 eventually-productive infection pathways, “hibernation” or “scavenger”; dependent on the presence or absence of the sigma factor which orchestrates E. coli's drastic stationary-phase adaptations, teaching the profound effects of global regulation systems.

(2) In some situations, we observed little initial phage absorption or host killing, followed by a surprising secondary very efficient killing and high phage production. Efforts at explanation led to obscure 1968 papers on “nascent phage,” novel baseplate fibers remain bound inside the host membrane – we think via a C-terminal transmembrane domain in gp7. These fragments somehow mediate productive infection that is independent of tail fiber – receptor interactions, and could destroy otherwise-resistant bacteria in therapeutic situations. In all these cases, fresh student viewpoints, thought provoking reading of classic works and innovative experiments are leading to important advances in our perception of phage biology as well as fostering student creativity, thirst for knowledge, and sense of membership in the scientific community.

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Last Updated: May 29, 2008

The Evergreen State College

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Olympia, Washington 98505

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