[Instability of host-virus association in Acholeplasma laidlawii infected by a mycoplasma virus of the Gourlay group L1].

Since L 1 Mycoplasmaviruses have been described by Gourlay for Acholeplasma laidlawii, two hypotheses tried to explain the relationships between virus and host, the first by a "gradual lysis", the second on the basis of a "reduced growth" of infected acholeplasmas. Neither has implied that susceptible cells, free of virus, can be obtained from infected populations, the cells being supposed to die according to the first and to be all infected but still slowly dividing according to the second hypothesis. However, we have shown, that uninfected susceptible cells do survive within infected acholeplasms. So, in the present work, we investigated the possibility that the susceptible cells may arise from a secondary dissociation between virus and host. Testing 51 clones for infectivity after isolation from two different A. laidlawii lines initially infected with two different strains of L 1 virus, we obtained 11 infected clones. The clones were studied for stability of association between virus and host. Six were shown not to be vertically stable during a serial reisolation procedure much longer than the usual cloning ("hypercloning"). Of the remaining 5 vertically stable lines, three were shown to be horizontally unstable when cloning was performed according to a multiple simultaneous technique. This indicates, that the association between virus and host cannot be considered stable and the virus is apparently of a pseudolysogenic type. Moreover, cell cloning is convenient to separate some cells from others, but may not be appropriate to isolate cells from viruses.(ABSTRACT TRUNCATED AT 250 WORDS)