Characteristics of Tφ3, a Bacteriophage for Bacillus stearothermophilus
A bacteriophage (Tφ3) which infects the thermophilic bacterium Bacillus stearothermophilus ATCC 8005 was isolated and characterized. Infection of the bacterium by the bacteriophage was carried out at 60 C, the optimal growth temperature of the host. At 60 C, the phage had a latent period of 18 min and a burst size of about 200. The phage was comparatively thermostable in broth. The halflife of Tφ3 was 400 min at 60 C, 120 min at 65 C, 40 min at 70 C, and 12 min at 75 C. The activation energy for the heat inactivation of Tφ3 was 56,000 cal. The buoyant density of Tφ3 in a cesium chloride density gradient was 1.526 g/ml. Electron micrographs of Tφ3 indicate that the phage has a head that is 57 mµ long. The dimensions and shape of the head are compatible with those of a regular icosahedron. Each edge of the head is 29 mµ long. The tail of Tφ3 is 125 mµ long and 10 mµ wide. There are about 30 cross-striations that are spaced at 3.9-mµ intervals along the tail. Under the conditions investigated, Tφ3 adsorbed slowly to the host. Only 2.8% of the phage adsorbed in 10 min at 60 C, the normal incubation temperature that was used. Tφ3 was not infective to four other thermophilic strains or to two mesophilic strains of bacteria.
Additional Information© 1967 American Society for Microbiology. Received for publication 11 January 1967 We express gratitude in behalf of the late Aleksandra Lielausis for his assistance with the electron microscopy. This investigation was supported by Public Health Service Predoctoral Fellowship GM 13,791 from the National Institute of General Medical Sciences. This work was submitted to the California Institute of Technology in partial fulfillment of requirements for the degree of Doctor of Philosophy.
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