I propose to initiate research on a specific group of bacteria, here denominated as the “Dehalococcoides-like Chloroflexi”. This group of bacteria is formed by several cultivated strains of the genus Dehalococcoides and many sequences of uncultivated organisms mostly from marine sediment or subsurface locations. All together form one subphylum of the Chloroflexi. Bacteria of the Dehalococcoides-like Chloroflexi are of particular importance for two independent reasons: first, the subphylum contains all bacteria known to transform under anaerobic conditions toxic and persistent halogenated compounds such as chlorinated dioxins, benzenes, biphenyls, vinyl chloride or brominated biphenylethers; secondly, massive amounts of Dehalococcoides-like Chloroflexi have recently been detected in marine organic-rich deep sediments dominating the populations with up to 80% of the total cell counts. However, many aspects of the physiology of Dehalococcoides species are unclear and almost nothing is known about Chloroflexi in deep sediments. I have worked for many years on the microbiology, biochemistry and genomics of Dehalococcoides species. With the proposed group I plan to focus on the physiological links between Chloroflexi in contaminated aquifers and those in marine sediments. Initially, cultures of marine sediment-Chloroflexi will be established in our lab and compared with pure Dehalococcoides strains. Objectives of our research towards marine Chloroflexi will be the description of the physiology, of the biochemistry of energy conservation and of key genes encoded in the genomes. It is anticipated that the research leads to a substantiated hypothesis on the mode of energy fixation in marine deep-sediments and an initial description of the role of Dehalococcoides-like Chloroflexi in biogeochemical cycles. We also expect to find insights into Chloroflexi evolution and their role in earth history by comparing genomes between Dehalococcoides species and marine Chloroflexi.
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