TAXONOMICAL CLASSIFICATION OF 20 NEWLY ISOLATED LISTERIA BACTERIOPHAGES BY ELECTRON-MICROSCOPY AND PROTEIN-ANALYSIS

A set of 20 newly isolated temperate bacteriophages for phage typing o f the pathogen Listeria monocytogenes has been investigated by means o f electron microscopy and electrophoretic analysis of phage structural proteins. All phages had isometric capsids (60-64 nm diameter), and l ong contractile or non-contractile tails of 170-320 nm length. They co uld be classified into 2 morphotypes (A1 and B1) and were assigned to 3 listeriaphage species (4211, 2671, and 2389). Individual protein pro files were generated by SDS-PAGE of viral polypeptides, as well as iso electric focusing of solubilized phage proteins in immobilized pH grad ient gels. The major structural proteins ranged in size from approxima tely 15 to 38 kD, and showed isoelectric points from pi 4.3 to 6.2. Pr otein compositions permitted the differentiation of individual phages as well as the recognition and grouping of similar viruses.