Novel mutant impaired in cell division: evidence for a positive regulating factor

A novel, conditional, cell-division mutant from Agmenellum quadruplicatum strain BG1 is described. During rapid growth in dilute suspensions, cell division lags behind mass increase and the cells form filaments. These filaments spontaneously divide into unit cell lengths as the culture density increases. Other conditions that favor the accumulation of metabolic products in the medium antagonize filament formations. An 80% ethanol-water extract of dried, spent medium also restores the ability of filaments to divide into cells of unit length. Our results suggest that at least one chemical factor acting as a positive effector is involved in cell division.