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Is the Temperature of Inactivation Different for Each Type of Phage?

CSEF · 2002 Microbiology

Kaitlin A. Kaufmann · Reyburn Intermediate, Clovis

Overview

Objectives/Goals The objective is to determine if temperature of inactivation is different for each type of bacteriophage. I believe this could be used as an easy field test to identify phage from field samples. Methods/Materials Dr. Cynthia Eayre, Research Plant Pathologist for USDA-ARS, and University of California, Davis provided phage samples. Crown Gall Bacteria (Agrobacterium spp.) was cultured by Dr. Eayre for my host. Research for a biological control for this economically harmful bacteria is being conducted due to the phase out of the soil fumigant Methyl Bromide. 40 phage samples have been screened for activity on Agrobacterium, but have not been specifically identified or classified. I used 4 of these with proven activity on the host. I prepared plates with pseudomonas agar, then a plaque of the host in a sloppy agar. I used a heat block to heat the 4 phage in water. Using a pipette I applied drops of phage onto the prepared plates starting at 30ºC and repeating at 5º increments. Each replication was a series of 5 temps (spread of 25º) and a control. 24-48 hours later I evaluated the results of the control of the bacteria. I repeated the process, increasing the temp range until all 4 phage inactivated. I repeated the inactivation levels a second time to confirm Results Each phage was repeatedly tested by Dr. Eayre for activity on Agrobacterium. By testing the activity on this host until a temperature was achieved with no activity I was able to determine the temperature of inactivation. The results show a different temperature for each phage used. Phage 1 unstable at 70ºC and inactivated at 75ºC; Phage 2 unstable at 50ºC and inactivated at 70ºC; Phage 3 unstable at 80ºC with inactivation at 90ºC; Phage 4 unstable at 85ºC with activity still present above 95ºC. Conclusions/Discussion Each phage sample did have a different temperature threshold. These tests supported my hypothesis of a different temperature of inactivation for each type of phage. Further identifying the phage through traditional methods will provide confirmation of my results. This test can be a very valuable tool in the bacteriophage work being done in many disciplines of research. A fast, inexpensive test to identify phage in field samples could provide valuable information early in work to being done to find cures for diseases around the world.

Summary statement

To see if temperature of inactivation can be used to identify bacteriophage.

Help received

Used lab facilities at USDA-ARS Research Station under the supervision of Dr. Cynthia Eayre.

Competition history

  • CSEF 2002 Microbiology · Entry J1319

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