Renoux, Gerard (Université de Montpellier, Montpellier, France), and Andree Suire. Spontaneous lysis and phage-carrier state in Brucella cultures. J. Bacteriol. 86:642–647. 1963.—When broth or saline suspensions of 60 randomly chosen Brucella strains were directly poured onto plates of Albimi Agar, distinct plaques, indicative of phage activity, developed. Unselected Brucella cultures containing cell types that gave rise to several morphologically distinct colonial types all proved to be naturally phage-infected. Selection and study of some of these colonial types led to the following conclusions: (i) S or SI colonies do not carry the phage and are sensitive to it; (ii) pure R colonies are phage-resistant and do not carry the phage; (iii) butyrous or sticky white P (“Porteuses”) colonies develop from “carrier cells” resistant to phage; and (iv) the progeny of cells of the P colony type segregate into cells that give rise to P, S, or SI colonies. However, when plates were streaked with a cotton swab soaked in the Brucella suspension, no visible plaque developed. The phenotypic changes occurring after phage infection are believed to play a role also under natural conditions; they are able to explain most of the natural behavior of Brucella. Their occurrence, however, does not exclude other genetic mechanisms that may produce similar phenotypic effects.

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