Project description:Previous studies have demonstrated that the iron content in marine heterotrophic bacteria is comparatively higher than that of phytoplankton. Therefore, they have been indicated to play a major role in the biogeochemical cycling of iron. In this study, we aimed to investigate the potential of viral lysis as a source of iron for marine heterotrophic bacteria. Viral lysates were derived from the marine heterotrophic bacterium, Vibrio natriegens PWH3a (A.K.A Vibrio alginolyticus). The bioavailability of Fe in the lysates was determined using a model heterotrophic bacterium, namely, Dokdonia sp. strain Dokd-P16, isolated from Fe-limited waters along Line P transect in the Northeastern Pacific Ocean. The bacteria were grown under Fe-deplete or Fe-replete conditions before being exposed to the viral lysate. Differential gene expression following exposure to the viral lysate was analyzed via RNA sequencing to identify differentially expressed genes under iron-replete and iron-deplete conditions. This study would provide novel insights into the role of viral lysis in heterotrophic bacteria in supplying bioavailable iron to other marine microorganisms under iron-limiting and non-limiting conditions. First, the marine heterotrophic bacterium genome, Dokdonia sp. strain Dokd-P16, was sequenced to provide a genomic context for the expression studies. Subsequently, the relative gene expression in Dokdonia sp. strain Dokd-P16 grown under Fe limiting and non-limiting conditions were analyzed. This transcriptomic approach would be utilized to elucidate genes regulated by Fe availability in Dokdonia sp. strain Dokd-P16, which indicate its Fe-related response viral lysate exposure. Taken together, in this study, the transcriptomic responses of Fe-limited and non-limited marine heterotrophic bacteria were analyzed, which provided novel insights into the biological availability of Fe from the viral lysates.
Project description:Influence of the constant full-spectrum light and short-to-long wavelengths of the visible spectrum (red, green and blue lights) and the significance of 12 h photoperiod was tested on heterotrophic marine flavobacteria Siansivirga zeaxanthinifaciens CC-SAMT-1T. RNA-seq analysis revealed remarkable qualitative and quantitative variations in terms of gene expression in CC-SAMT-1T with respect to incident lights. While blue light illumination stimulated expression of genes involved in inorganic carbon metabolism, green˗red lights largely upregulated the genes participating in high-molecular-weight (HMW) organic carbon metabolism. Constant full-spectrum light also displayed the upregulation of genes involved in the metabolism of HMW organic carbon. Thus, the short-to-long wavelengths of visible light and the 12 h photoperiod most likely to play a key role in the marine carbon cycle by tuning heterotrophic bacterial metabolism.
Project description:The available energy and carbon sources for prokaryotes in the deep ocean remain still largely enigmatic. Reduced sulfur compounds, such as thiosulfate, are a potential energy source for both auto- and heterotrophic marine prokaryotes. Shipboard experiments performed in the North Atlantic using Labrador Sea Water (~2000 m depth) amended with thiosulfate led to an enhanced prokaryotic dissolved inorganic carbon (DIC) fixation.
Project description:This project describes the protein composition of the Cafeteria roenbergensis virus (CroV, strain BV-PW1: TaxID 693272) particle, a giant marine DNA virus that infects the heterotrophic nanoflagellate microeukaryote C. roenbergensis. CroV is a member of the Nucleo-Cytoplasmic Large DNA Virus clade and related to Acanthamoeba polyphaga mimivirus. CroV possesses a DNA genome of ~730 kilobase pairs that encodes 544 predicted proteins. We analyzed the protein composition of purified CroV particles by liquid chromatography - tandem mass spectrometry (LC-MS/MS) and identified 141 virion-associated CroV proteins. Predicted functions could be assigned to 37% of these proteins, which include structural proteins as well as enzymes for transcription, DNA repair, redox reactions and protein modification. Homologs of 36 CroV virion proteins have previously been found in the virion of Acanthamoeba polyphaga mimivirus. This study shows that giant DNA virus particles contain more than one hundred viral proteins that include specific enzymatic functions.
Project description:The ubiquitous heterotrophic marine bacterium, Rugeria pomeroyi, was experimentally cultured under both environmentally realistic carbon conditions and with a tracer-level addition of 13C-labeled leucine. Bacterial protein biosynthesis was tracked through exponential and stationary growth phases. This combination of methods allowed for observation of real-time bacterial protein production of an environmentally relevant marine bacterium under low-carbon conditions to understand metabolic priorities during different growth phases.