Pigmentation phenotype instability in Myxococcus xanthus

Abstract

Cells of Myxococcus xanthus FB2 produce tan or yellow colonies. Subcultures of tan colonies yielded tan and yellow colonies and subcultures of most yellow colonies yielded only yellow colonies. Strain FB2 variants in which the color type is more stable were obtained. Yellow cells were distinguishable from tan by the presence of pigment(s) with an absorption maximum at 379 nm. Fluctuation Test experiments and the presence of this pigment(s) in liquid cultures of FB2 indicated that tan phenotype cells spontaneously became or segregated yellow cells in liquid culture. The frequency of appearance of yellow cells was increased in low density cultures (less than 10(6)/ml). The increase cannot be explained by differences in growth rates of the two phenotypes. No evidence that cell-cell contact or culture medium constituents affect the appearance of the yellow phenotype was found. Ultraviolet irradiation of FB2 resulted in an increased proportion of cells producing yellow colonies among the survivors. Greater UV resistance of yellow cells and UV-induced conversion of tan to yellow accounts for this increase. Low level photoreactivation of viability and of the tan phenotype occurred. Incubation of FB2 in medium containing mitomycin C, nalidixic acid, phenethyl alcohol, or at 36.5 degrees C also resulted in conversion of tan to yellow cells.

Effects of glucosamine on lysis, glycerol formation, and sporulation in Myxococcus xanthus

“…At the lower concentrations of GlcN, the extent of lysis was highly variable from day to day. This was found to depend on the relative concentrations of yellowand tan-colony-phase variants (7) in the original vegetative population. Although little is known about the mechanism of phase variation and the function of the different cell types, it may be that the two colony types play different roles during development (40).…”

“…M. xanthus undergoes a phase variation that can be detected by observing a switch in colony color from yellow to tan (7,8). Although it is not known whether or not this phase variation plays a role in development, it has become evident that tan cells play a role in GlcN-mediated events.…”

The unique DKxanthene secondary metabolite family from the myxobacterium Myxococcus xanthus is required for developmental sporulation

“…Despite their structural novelty, the involvement of these pigments in the myxobacterial life cycle has been described almost 30 years ago. In 1977, Burchard et al (36) stated that ''a better understanding of the Y phenotype and its expression will come with characterization of P379 and its biosynthetic pathway . .…”

Role of Phase Variation in the Resistance of Myxococcus xanthus Fruiting Bodies to Caenorhabditis elegans Predation

“…In its vegetatively growing state, M. xanthus can undergo phase variation between two different cell types that can form yellow or tan colonies (6). Tan variants are generally considered to be nonpigmented, while yellow variants produce a polar, acetone-soluble pigment with an absorbance maximum at 379 nm (5,6). Because tan and yellow cells can interconvert, this is considered an example of true phase variation.…”

“…Environmental factors influence the proportions of yellow and tan variants in a population (28). Conditions that increase the production of yellow cells include the presence of high nutrient concentrations, UV radiation, low cell density, incubation at 36.5°C (the normal growth temperature is 32°C), and incubation in medium containing mitomycin C, nalidixic acid, or 2-phenylethanol (5,29). These observations suggest that phase shifting to the yellow variant may be linked with M. xanthus stress responses.…”