Project description:Cryptomonas sp. was grown under phototrophic conditions, glucose supplemented phototrophic conditions and 3 different dissolved organic carbon (DOC) concentrations: 1.5, 30 and 90 mg C l−1. The objective was to study the adaptations that make Cryptomonas sp. thrive under high DOC conditions.
Project description:Here we show that the phytochrome-less chlorophyte Chlamydomonas reinhardtii retains a functional pathway to synthesize the linear tetrapyrrole (bilin) precursor of the phytochrome chromophore. Reverse genetic, metabolic inactivation and bilin rescue experiments establish that this pathway is needed for heme iron acquisition and for the diurnal transition to phototrophic growth. RNA-Seq measurements reveal a bilin-dependent signaling network that is necessary for the heterotrophic to phototrophic transition. These results imply the presence of a novel bilin sensor pathway that may be widely distributed amongst oxygenic photosynthetic organisms.
Project description:In nature, bacteria reside in biofilms - multicellular differentiated communities held together by extracellular matrix. In this work, we identified a novel subpopulation essential for biofilm formation – mineral-forming cells in Bacillus subtilis biofilms. This subpopulation contains an intracellular calcium-accumulating niche, in which the formation of a calcium carbonate mineral is initiated. As the biofilm colony develops, this mineral grows in a controlled manner, forming a functional macrostructure that serves the entire community. Consistently, biofilm development is prevented by inhibition of calcium uptake. Taken together, our results provide a clear demonstration of the orchestrated production of calcite exoskeleton, critical to morphogenesis in simple prokaryotes. We expect future research exploring this newly discovered process to shed further light on mechanisms of bacterial development.
Project description:Here we show that the phytochrome-less chlorophyte Chlamydomonas reinhardtii retains a functional pathway to synthesize the linear tetrapyrrole (bilin) precursor of the phytochrome chromophore. Reverse genetic, metabolic inactivation and bilin rescue experiments establish that this pathway is needed for heme iron acquisition and for the diurnal transition to phototrophic growth. RNA-Seq measurements reveal a bilin-dependent signaling network that is necessary for the heterotrophic to phototrophic transition. These results imply the presence of a novel bilin sensor pathway that may be widely distributed amongst oxygenic photosynthetic organisms. We isolated RNA from heterotrophic suspension cultures of 4A+ WT and the hmox1 mutant grown in the presence or absence of 0.1 mM BV IXM-NM-1 before and after transfer to low light.
Project description:Habitat connectivity and environmental controls on the structure of phototrophic microbial mats and bacterioplankton communities in an Antarctic freshwater system
Project description:Microbial autotroph-heterotroph interactions influence biogeochemical cycles on a global scale, but the diversity and complexity of natural systems and their intractability to in situ manipulation make it challenging to elucidate the principles governing these interactions. The study of assembling phototrophic biofilm communities provides a robust means to identify such interactions and evaluate their contributions to the recruitment and maintenance of phylogenetic and functional diversity overtime. To examine primary succession in phototrophic communities, we isolated two unicyanobacterial consortia from the microbial mat in HotLake, Washington, characterizing the membership and metabolic function of each consortium. We then analyzed the spatial structures and quantified the community compositions of their assembling biofilms. The consortia retained the same suite of heterotrophic species, identified as abundant members of the mat and assigned to Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. Autotroph growth rates dominated early in assembly, yielding to increasing heterotroph growth rates late in succession. The two consortia exhibited similar assembly patterns, with increasing relative abundances of members from Bacteroidetes and Alphaproteobacteria concurrent with decreasing relative abundances of those from Gamma proteobacteria. Despite these similarities at higher taxonomic levels, the relative abundances of individual heterotrophic species were substantially different in the developing consortial biofilms. This suggests that, although similar niches are created by the cyanobacterial metabolisms, the resulting webs of autotroph-heterotroph and heterotroph-heterotroph interactions are specific to each primary producer. The relative simplicity and tractability of the Hot Lake unicyanobacterial consortia make them useful model systems for deciphering interspecies interactions and assembly principles relevant to natural microbial communities.
