Photomorphogenesis of Myxococcocus macrosporus: New Insights for Light-Regulation of Cell Development

Myxobacteria are social bacteria distinguished among prokaryotes by a multicellular stage in their life cycle known as fruiting bodies formations, which is a response to nutrient deprivation. Additionally, fruiting body formation in Stigmatella aurantiaca is stimulated by light. Genome sequence of Myxococcus macrosporus, revealed the presence of a red-light photoreceptor, bacteriophytochrome (BphP), found in photosynthetic and non-photosynthetic bacteria. BphPs belong to a large phytochrome family of photoreceptors originally discovered in plants, where they are directly linked to the circadian clock genes. BphPs have been implicated in carotenoid synthesis, motility, and photodynamic stress in non-photosynthetic bacteria. The role of the BphPs in M. macrosporus remains unknown although it has been linked to fruiting body formation in related S. aurantiaca. We have observed that M. macrosporus displays differential photomorphogenic behaviors under constant light, and 12:12 hour light/dark (LD) cycle as compared to constant dark (DD) conditions. We hypothesize that BphP plays a role in these behaviors. In this study we demonstrate light and nutrient dependent pattern of fruiting bodies development in Myxococcus macrosporus HW-1. Additionally, we characterized light induced differential gene expression with the special focus on the circadian clock, and carotenoid biosynthesis genes in M. macrosporus and M. xanthus. We incubated vegetative cells of M. xanthus and M. macrosporus in constant darkness (DD) or 12:12 light dark (LD) cycle. Samples of stationary cells were collected at 36 hours post inoculation from DD and LD cultures to investigate impact of light on gene expression of above mentioned myxobacteria.