Intellectual merit. The focus of this project on energy metabolism and quorum sensing in Caminibacter mediatlanticus is particularly important as this dominant deep-sea vent bacterium occupies the bottom of the chemosynthesis-based food chain. This study is the first to collect physiologically relevant data about primary producers at these sites, which will provide major insights on microbial gene regulation and expression in response to changing conditions in the environment. Building on information gained from the genome sequence of this organism, this project will combine physiological experiments, carried out using batch, continuous cultures, and in-situ incubations, with the quantification of the expression of specific genes (by qRT-PCR). The significance of the proposed study rests in the fact that gene expression in C. mediatlanticus will be investigated under growth conditions that reflect, in terms of concentrations of nutrients, those actually encountered by this organism in its natural environment. Such genome-enabled studies are critical to acquire fundamental information on gene expression in organisms that are ecologically relevant in their natural habitat, and to bridge the gap between laboratory-based investigations of pure cultures and environmental studies of natural microbial communities. The biotechnological uses of these organisms are likely to have significant impact across many fields.
Broader impact. This project will offer training opportunities to one graduate student. Several undergraduate students as well as high school students are also involved in the project. A collaboration with the Mid-Atlantic Center for Ocean Science Education Excellence (COSEE) will help to translate the research for K-12 and public audiences. Furthermore, the Deep-Sea Microbiology Lab website, featured by the National Science Digital Library Scout Report for the Life Sciences, will ensure the rapid and wide dissemination of the results from this research.
Of all environments on Earth at which life flourishes, deep-sea volcanoes are probably the most extreme. Temperatures within many of these systems range from 2-400°C, pressures are in excess of several hundred atmospheres, and concentrations of hydrogen sulfide and many heavy metals (e.g., Cu, Zn, Fe, Cd, Pb) frequently exceed levels normally considered toxic to biological systems. During the cycling of seawater through the earth's crust along the mid-oceanic ridge system, the reaction of seawater with crustal rocks at high temperatures enriches the hydrothermal fluids with reduced organic and inorganic chemical species. The hydrothermal fluids are then emitted from warm (≤ 25°C) and hot (~350°C) submarine vents at depths reaching about 4000 m (Fig. 1). Since sunlight does not reach the deep ocean, the organisms that inhabit deep-sea vents do not rely on photosynthesis for the production of organic carbon. Instead, microbes that colonize deep-sea vents take advantage of redox gradients (e.g., oxic/anoxic region between oxygen-depleted hydrothermal fluids and oxygen-rich seawater) to mediate the transfer of chemical energy into biochemical energy (e.g., ATP). Microbes then use the energy stored in ATP to synthesize organic carbon from carbon dioxide, a process overall known as chemosynthesis (synthesis of organic carbon using chemical energy). Microbial chemosynthesis represents the basis for primary production at deep-sea hydrothermal vents. The flux of energy from the geothermal source via emitted reduced chemical species is mediated by microbial transformations, which result in the production of ATP and organic carbon as a form of biochemical energy. Chemosynthesis may be coupled to both aerobic and anaerobic respiration. Aerobic chemosynthesis depends on oxygen, which ultimately originates from photosynthetic processes occurring in the photic zone. Anaerobic chemosynthesis depends on terminal electron acceptors other than oxygen (e.g., S0, SO42-, CO2, Fe3+, NO3-, etc.), and therefore it is independent from photosynthetic processes. The focus of this project is to investigate the metabolic and physiological strategies of Caminibacter mediatlanticus, a thermophilic, anaerobic chemosynthetic bacterium that we isolated from a deep-sea hydrothermal vent. Intellectual merit. This project combined physiological experimentswith the quantification of the expression of specific genes involved in anaerobic, respiration, carbon fixation and cell-to-cell communication in the deep-sea vent bacterium Caminibacter mediatlanticus, using information derived from the genome sequence of this organism. Such genome-enabled studies are critical to acquire fundamental information on gene expression in organisms that are ecologically relevant in their natural habitat, and to bridge the gap between laboratory-based investigations of pure cultures and environmental studies of natural microbial communities. Broader impact. This project offered training opportunities to two graduate students. Results from this study were published in peer-reviewed journals and disseminated at conferences, invited talks and lectures. Furthermore, the Deep-Sea Microbiology Lab website (http://marine.rutgers.edu/deep-seamicrobiology/), featured by the National Science Digital Library Scout Report for the Life Sciences, along with a web page dedicated to research in deep-sea microbiology (http://marine.rutgers.edu/main/Exciting-Science/Exciting-Science-Life-at-the-Extremes-Microbiology-of-deep-sea-volcanoes.html), presents an overview of the research done in the laboratory of the PI.
