Browsing by Author "Tal, Yossi"
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Item Anaerobic Ammonia-Oxidizing Bacteria and Related Activity in Baltimore Inner Harbor Sediment(American Society for Microbiology, 2005-04) Tal, Yossi; Watts, Joy E. M.; Schreier, Harold J.The discovery of bacteria capable of anaerobic ammonia oxidation (anammox) has generated interest in understanding the activity, diversity, and distribution of these bacteria in the environment. In this study anammox activity in sediment samples obtained from the Inner Harbor of Baltimore, Md., was detected by (15)N tracer assays. Anammox-specific oligonucleotide primer sets were used to screen a Planctomycetales-specific 16S rRNA gene library generated from sediment DNA preparations, and four new anammox bacterial sequences were identified. Three of these sequences form a cohesive new branch of the anammox group, and the fourth sequence branches separately from this group. Denaturing gradient gel electrophoresis analysis of sediment incubated with anammox-specific media confirmed the presence of the four anammox-related 16S rRNA gene sequences. Evidence for the presence of anammox bacteria in Inner Harbor sediment was also obtained by using an anammox-specific probe in fluorescence in situ hybridization studies. To our knowledge, this is the first report of anammox activity and related bacterial 16S rRNA gene sequences from the Chesapeake Bay basin area, and the results suggest that this pathway plays an important role in the nitrogen cycle of this estuarine environment. Furthermore, the presence of these bacteria and their activity in sediment strengthen the contention that anammox-related Plactomycetales are globally distributed.Item Stimulating Denitrification in a Marine Recirculating Aquaculture System Biofilter Using Granular Starch as a Carbon Source(Internal Journal of Recirculating Aquaculture, 2008) Morrison, Megan M.; Tal, Yossi; Schreier, Harold J.Maintaining superior water quality in intensive recirculating aquaculture systems (RAS) by controlling levels of inorganic nitrogenous waste—ammonia, nitrate and nitrite—derived from uneaten food and fecal excretion is often a challenge. In most systems, solids are removed mechanically and ammonia is oxidized to nitrate by nitrifying biological filtration; nitrate is subsequently eliminated through numerous water exchanges. Alternatively, nitrate removal is achieved using a bacterial-mediated denitrification component that reduces nitrate to nitrogen gas under anoxic conditions, a process that depends on the application of external or endogenous electron and carbon donors, e.g. carbohydrates or organic alcohols. In this study, we compared the capacity of acetate, glucose, soluble starch, and granular starches to promote the denitrifying activity of heterotrophic bacteria in biofilm-coated polyethylene beadsfrom a marine RAS moving bed bioreactor (MBB) under anaerobic conditions. Granular starches (corn, wheat, and rice) were as effective as glucose in supporting denitrification, and were 7.6 and 9.8 times more effective in removing nitrate when compared to soluble starch and acetate, respectively. Furthermore, granular starches retained their denitrification potential for longer time periods than soluble starch or acetate. The low cost, ease of use, and non-toxic nature of granular starches make them an ideal exogenous carbon source for promoting denitrification in RAS bioreactors.