Several strains of phages active against Streptococcus thermophilus and species of Lactobacillus were examined with an electron microscope after negative staining with phospho-tungstic acid or uranyl acetate. S. thermophilus bacteriophage exhibited exceptionally long tails (polytails). The width and structure of the polytail was the same as a normal phage tail, 10 nm, but was 2 to 4 times longer, 480–960 nm. Preparations revealed extensive adsorption of S. thermophilus bacteriophage to broken bacterial cell walls. One strain of S. thermophilus phage had a spherical structure at the posterior end of its tail. The bacteriophages of Lactobacillus bulgaricus and Lactobacillus helveticus had a distinct contractile tail sheath, whereas Lactobacillus lactis phage did not.

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Author notes

1Journal Paper No. J-9912 of Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2144.

2Research and Development, Leprino Foods Company, 1830 W. 38th Ave., Denver, Colorado 80211.

3American Dairy-food Consultants, Inc. (ADC) 2460 South Broadway, Denver, Colorado 80210.