Pseudolysogeny in Mycobacterium diernhoferi ATCC19341.

Abstract

Lysogeny is characterized by the stable integration of the bacteriophage genome (the prophage) with the bacterial chromosome (Jacob & Wollman, 1959). There are however a number of host-phage relationships, collectively referred to as pseudolysogeny, in which the prophage appears to coexist in a temperate state with the host but without the occurrence of a stable inheritable union of their respective genomes. The literature concerning pseudolysogeny has been reviewed by Baess (1971). In a form of pseudolysogeny referred to as the carrier state (Hayes, 1968), the prophage is carried within the bacterium as an episome-like unit which does not replicate in sequence with the bacterial chromosome. Thus, in contrast to true lysogeny, the prophage is only transmitted to a minority of the progeny. However, in some bacteria the phages undergo replication with lysis of the host and reinfection of surrounding phage-free bacteria, thus maintaining the presence of the phage in the culture. The cycle of curing and reinfection may be blocked by culturing the strain in the presence of an antiserum or other substances capable of neutralizing the extracellular phages. Strains of bacteria exhibiting pseudolysogeny of the carrier-state type are detectable by observing the spontaneous appearance of phage plaques when cultured on suitable solid media. Beck (1965) described a strain of Mycobacterium fortuitum, referred to as strain C.U. This strain was found to be pseudolysogenic by Baess (1971) who isolated phage BK5 from the spontaneously-appearing plaques. Subsequently the phenomenon was observed in two other strains of M. fortuitum, ATCC23029 (I. Baess, personal communication) and ATCC 23041 (Nordstrom & Grange, 1974). In addition a form of pseudolysogeny was observed in Mycobacterium smegmatis ATcC607 after the experimental infection of this strain with phage LI (Tokunaga & Sellers, 1970). It was therefore of interest to determine whether pseudolysogeny occurred naturally in mycobacterial species other than M. fortuitum. This paper reports the occurrence of pseudolysogeny in Mycobacterium diernhoferi ATCC 19341, which was observed during a study of roo rapidly growing mycobacteria representing twelve different species. METHODS