CELL DEATH DURING FRUITING BODY FORMATION IN MYXococcus

Abstract

Massive cell death occurs during fruiting construction by several species of Myxococcus . The events which occur lead us to the hypothesis that regulated senescence and cell death are integral part of myxobacterial development. During fruiting body formation by M. xanthus 60 - 8) % of the vegetative cells lyse. The majority of the survivina cells are eventually converted to myxospores in the fruiting body. This lysis has been measured both by the loss of 3y-methy1 thymidine label from DHA of the cells and by actual cell counts. Such lysis occurs under a variety of conditions leading to fruiting body formation. We have also demonstrated lysis during fruiting body formation in Myxococcus fulvus and Myxococcus virescens. If cells are removed at various times during fruiting body formation and replaced in a liquid growth medium the tendency to lyse is reversible until the fruiting bodies have formed; at that time the vegetative cells become irreversibly committed to lysis. We suggest that lysis in the organisms we have examined is a functional and necessary part of the developmental cycle. It is possible that the lysing cells are providing a source of biosynthetic precursors and/or a source of energy for the formation of myxospores and/or fruitina bodies.