Ultrastructure and Lytic Activity of Bacteriophages Isolated from Cheese Wheys

¹ Department of Food Science, Cornell University, Ithaca, NY 14853-7201

Ultrastructural Characteristics of representative bacteriophages of Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris were studied using transmission electron microscopy to determine the types of phages found in infected whey samples. Two morphological head types were observed, prolate and isometric (3 prolate and 13 isometric). All 3 prolate phages lysed a variety of relatively resistant host strains. Four isometric phages also demonstrated this ability. Prolate head width ranged from 38.3 to 47.6 nm, and head length ranged from 59.4 to 67.9 nm. Isometric head widths ranged from 49.5 to 62.0 nm. Tail length of the prolate phages ranged from 103.7 to 119.1 nm, and the tail length of the isometric phages ranged from 123.9 to 179.5 nm. No neck collars, appendages, or tail fibers were observed. Biological activity of representative isometric and prolate phages remained stable after storage in M17 and 10% M17 broths, but stability in CsCl phage buffer was variable.

Key Words: ultrastructure • bacteriophage • Lactococcus lactis