Myxococcus xanthus developmental cell fate production: heterogeneous accumulation of developmental regulatory proteins and reexamination of the role of MazF in developmental lysis

Myxococcus xanthus undergoes a starvation-induced multicellular developmental program during which cells partition into three known fates: (i) aggregation into fruiting bodies followed by differentiation into spores, (ii) lysis, or (iii) differentiation into nonaggregating persister-like cells, termed peripheral rods. As a first step to characterize cell fate segregation, we enumer-ated total, aggregating, and nonaggregating cells throughout the developmental program.We demonstrate that both cell lysis and cell aggregation begin with similar timing at approximately 24 h after induction of development. Examination of several known regulatory proteins in the separated aggregated and nonaggregated cell fractions revealed previously unknown heteroge-neity in the accumulation patterns of proteins involved in type IV pilus (T4P)-mediated motility (PilC and PilA) and regulation of development (MrpC, FruA, and C-signal). As part of our characterization of the cell lysis fate, we set out to investigate the un-orthodoxMazF-MrpC toxin-antitoxin system which was previously proposed to induce programmed cell death (PCD).We dem-onstrate that deletion ofmazF in two different wild-typeM. xanthus laboratory strains does not significantly reduce develop-mental cell lysis, suggesting that MazF’s role in promoting PCD is an adaption to the mutant background strain used previously. The myxobacteria are excellent model systems for multicellularbacterial behavior.Myxococcus xanthus, the best studied of this group of bacteria, exhibits a complex life cycle. Under nutrient-replete conditions, cells swarm over surfaces, obtaining nutrients cooperatively by secreting sufficient degradative enzymes to diges