The Growth in vitro of Killer Particles from Paramecium aurelia and the Axenic Culture of this Protozoon

Abstract

S U M M A R YParamecia belonging to certain strains of Parameciunz aurelia (syngens I , 2 and 8) were transferred from dual culture with bacteria to axenic media, where the growth of some stocks continued, with weekly subculturing. The only axenically grown stock found to be capable of supporting growth of mu particles indefinitely was stock 138 (syngen 8).Lambda and mu particles from axenically grown Paramecium aurelia were cultivated in vitro in a highly complex medium at 27O under aerobic conditions. The particles retained their characteristic killing action on certain P. aurelia stocks but could not infect sensitive paramecia. The particles divided at approximately one fission per day and achieved a maximum density of only 16-20 x 103/ml. The implications of these studies for the interaction of the nuclear genes and the killer particles are discussed.

Kappa and other endosymbionts in Paramecium aurelia.

“…Cell-to-cell contact, but not nuclear transfer, is necessary for mate-killing. (Yet see the recent report of Williams [154] discussed in the section on host-free culture. )…”

A study on the mate-killer toxin by microinjection inParamecium

“…Mate-killer action by mu in any way other than cell to cell contact at conjugation has never been found (Preer et al 1974). One exception was, however, found with in vitro cultured mu in which 138 mu kills lambda free 299 paramecia (Williams, 1971).…”

R-body-producing bacteria.

“…Endosymbionts in Para,linec(ium species exhibit varying degrees of autonomy. The symbionts mu (128) and lambda (123,128) have reportedly been cultured outside their hosts in axenic media, although their growth is extremely poor. Kappa particles have not been cultured outside their hosts, despite much effort to do so, and are therefore considered obligate endosymbionts, dependent on Paramnecium-encoded products for their survival (76).…”