The Molecular Mechanism Of Photomorphogenic Response In The Non-Photosynthetic Myxobacteria S. Aurantiaca And M. Fulvus
Abstract
Non-photosynthetic myxobacteria are distinguished among prokaryotes by a multicellular stage in their life cycle known as fruiting bodies, formed only under starvation conditions. Interestingly, in Stigmatella aurantiaca and Chondromyces apiculatus fruiting bodies are stimulated by light. This photomorphogenic phenomenon was demonstrated in the late 1970s, decades prior to the first characterization of protein photoreceptors from eubacteria. Specifically, genes that code for the blue light (photoactive yellow protein PYP) and/or red-light (bacteriophytochromes BphPs) photoreceptors are found across all three suborders of myxococcales. However, their role remains largely unknown. Furthermore, the genetic mechanisms underlying fruiting body formation and visible light response are not conserved in myxococcales. We hypothesize that BphPs and PYPs play a critical role in fruiting body assembly of myxococcales that display photomorphogenic response. To address this question, we focused on S. aurantiaca that has two BphPs and one PYP genes and previously uncharacterized M. fulvus that has a single BphP gene and lacks PYPs. To induce photomorphogenesis in S. aurantiaca DW4/3.1 and M. fulvus HW-1, cells were cultured on starvation agar media as well as filter paper under dark, white, red, far-red and blue lights at 32°C and 30°C, respectively. Data was recorded by photographing the fruiting body clusters at different magnifications with ZEN lite software and quantified using ImageJ. Larger fruiting body clusters of S. aurantiaca that were darker in color formed under the blue and far-red lights conditions. Furthermore, concentric rings of fruiting bodies formed in M. fulvus under constant light conditions compared to those under an 18:6 hour day/night cycle. Interestingly, genomes of S. aurantiaca and M. fulvus carry the homolog of cyanobacterial KaiC gene implicated in the circadian clock regulation. Currently, we are developing the molecular mechanism of fruiting body formation in S. aurantiaca and M. fulvus with respect to light by inactivating/deleting genes coding for BphPs and/or KaiC homolog and screening for resulting phenotypes. Our future goal is to determine mechanistic changes that accompany photomorphogenesis in myxobacteria and the novel role of photoreceptors in these non-photosynthetic microorganisms.
The Molecular Mechanism Of Photomorphogenic Response In The Non-Photosynthetic Myxobacteria S. Aurantiaca And M. Fulvus
Non-photosynthetic myxobacteria are distinguished among prokaryotes by a multicellular stage in their life cycle known as fruiting bodies, formed only under starvation conditions. Interestingly, in Stigmatella aurantiaca and Chondromyces apiculatus fruiting bodies are stimulated by light. This photomorphogenic phenomenon was demonstrated in the late 1970s, decades prior to the first characterization of protein photoreceptors from eubacteria. Specifically, genes that code for the blue light (photoactive yellow protein PYP) and/or red-light (bacteriophytochromes BphPs) photoreceptors are found across all three suborders of myxococcales. However, their role remains largely unknown. Furthermore, the genetic mechanisms underlying fruiting body formation and visible light response are not conserved in myxococcales. We hypothesize that BphPs and PYPs play a critical role in fruiting body assembly of myxococcales that display photomorphogenic response. To address this question, we focused on S. aurantiaca that has two BphPs and one PYP genes and previously uncharacterized M. fulvus that has a single BphP gene and lacks PYPs. To induce photomorphogenesis in S. aurantiaca DW4/3.1 and M. fulvus HW-1, cells were cultured on starvation agar media as well as filter paper under dark, white, red, far-red and blue lights at 32°C and 30°C, respectively. Data was recorded by photographing the fruiting body clusters at different magnifications with ZEN lite software and quantified using ImageJ. Larger fruiting body clusters of S. aurantiaca that were darker in color formed under the blue and far-red lights conditions. Furthermore, concentric rings of fruiting bodies formed in M. fulvus under constant light conditions compared to those under an 18:6 hour day/night cycle. Interestingly, genomes of S. aurantiaca and M. fulvus carry the homolog of cyanobacterial KaiC gene implicated in the circadian clock regulation. Currently, we are developing the molecular mechanism of fruiting body formation in S. aurantiaca and M. fulvus with respect to light by inactivating/deleting genes coding for BphPs and/or KaiC homolog and screening for resulting phenotypes. Our future goal is to determine mechanistic changes that accompany photomorphogenesis in myxobacteria and the novel role of photoreceptors in these non-photosynthetic microorganisms.