ABSTRACT: General features of the marine lysogenic bacterium H24 are described. The bacterial strain was isolated from a sample of North Sea water in 1978. After several consecutive transfers on seawater agar slants spontaneous plaque-formation was observed in 1981. When H24 was grown in bouillon the cultures were found to contain plaque forming units (PFU) at any number between zero and 10⁹ ml^-1, indicating that spontaneous plaque formation was due to mutational events. Cultures with the highest contents of PFU hardly differed in turbidity from cultures lacking PFU. These observations are ascribed to pseudolysogeny, i.e. immunity of cells against the phage present. When a cured derivative, H24(L10), became available the wild-type phage phiH24 residing in H24 was isolated and shown to re-lysogenize H24(L10). It also enabled differentiation between virulent and non-virulent mutants. Mutants of phiH24 were found to induce pseudolysogeny. Upon streaking on nutrient agar, material from colonies of pseudolysogenized cells produced various kinds of colonies representing clones of fully sensitive cells, of pseudolysogenized cells, or of mixtures of both. This and accompanying papers report the first intensive studies of a marine lysogenic bacterium.

KEY WORDS: Marine · Bacteria · Lysogeny · Phage · Mutation · Pseudolysogeny

Published in MEPS Vol. 148 (1997) on February 27
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997