Ultrastructures of Bacteriophages Active Against Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus lactis and Lactobacillus helveticus

Abstract

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.