Project description:In this study, we provide a time-series analysis of the transcriptional response of Gemmatimonas phototrophica AP64T during the dark-to-light transition under aerobic and semiaerobic conditions. By analysing its transcriptome, focussing especially on PS-related genes, we tested the hypothesis that G. phototrophica might constitute an example of an anoxygenic phototroph on its evolutionary pathway from anaerobic to aerobic life-style.
Project description:In this study, we provide a time-series analysis of the transcriptional response of Gemmatimonas phototrophica AP64T during the dark-to-light transition under aerobic and semiaerobic conditions. By analysing its transcriptome, focussing especially on PS-related genes, we tested the hypothesis that G. phototrophica might constitute an example of an anoxygenic phototroph on its evolutionary pathway from anaerobic to aerobic life-style.
Project description:In this study, we provide a time-series analysis of the transcriptional response of Gemmatimonas phototrophica AP64T during the dark-to-light transition under aerobic and semiaerobic conditions. By analysing its transcriptome, focussing especially on PS-related genes, we tested the hypothesis that G. phototrophica might constitute an example of an anoxygenic phototroph on its evolutionary pathway from anaerobic to aerobic life-style.
Project description:Draft genome sequence of aerobic anoxygenic phototrophic bacterium Roseobacter sp. OBYS 0001, isolated from a coastal seawater in Otsuchi Bay, Japan
Project description:Bacteria have evolved many strategies to spare energy when nutrients become scarce. One widespread such strategy is facultative phototrophy, which helps heterotrophs supplement their energy supply using light. Our knowledge on the impact that such behaviors have on bacterial fitness and physiology is, however, still limited. Here, we study how a representative of the genus Porphyrobacter, in which aerobic anoxygenic phototrophy is ancestral, responds to different light regimes under nutrient limitation. We show that bacterial survival in stationary phase relies on functional reaction centers and varies depending on the light regime. Under dark‑light alternance, our bacterial model presents a diphasic life history dependent on phototrophy: during dark phases, the cells inhibit DNA replication and part of the population lyses and releases nutrients, while subsequent light phases allow for the recovery and renewed growth of the surviving cells. We correlate these cyclic variations with a pervasive pattern of rhythmic transcription which reflects global changes in diurnal metabolic activity. Finally, we demonstrate that, compared to either a phototrophy null mutant or a bacteriochlorophyll a overproducer, the wild type strain is better adapted to natural environments, where regular dark‑light cycles are interspersed with additional accidental dark episodes. Overall, our results highlight the importance of light‑induced biological rhythms in a new model of aerobic anoxygenic phototroph representative of an ecologically important group of environmental bacteria.
Project description:Spinae are tubular surface appendages broadly found in Gram-negative bacteria. Little is known about their architecture, function or origin. Here, we report structural characterization of the spinae from marine bacteria Roseobacter sp. YSCB. Electron cryo-tomography revealed that a single filament winds into a hollow flared base with progressive change to a cylinder. Proteinase K unwound the spinae into proteolysis-resistant filaments. Thermal treatment ripped the spinae into ribbons that were melted with prolonged heating. Circular dichroism spectroscopy revealed a dominant beta-structure of the spinae. Differential scanning calorimetry analyses showed three endothermic transformations at 50-85°C, 98°C and 123°C, respectively. The heating almost completely disintegrated the spinae, abolished the 98°C transition and destroyed the beta-structure. Infrared spectroscopy identified the amide I spectrum maximum at a position similar to that of amyloid fibrils. Therefore, the spinae distinguish from other bacterial appendages, e.g. flagella and stalks, in both the structure and mechanism of assembly.
