title: Biphasic behavior of anammox regulated by nitrite and nitrate in an estuarine sediment.
abstract: The production of N2 gas via anammox was investigated in sediment slurries at in situ NO2- concentrations in the presence and absence of NO3-. With single enrichment above 10 microM 14NO2- or 14NO3- and 15NH4+, anammox activity was always linear (P < 0.05), in agreement with previous findings. In contrast, anammox exhibited a range of activity below 10 microM NO2- or NO3-, including an elevated response at lower concentrations. With 100 microM NO3-, no significant transient accumulation of NO2- could be measured, and the starting concentration of NO2- could therefore be regulated. With dual enrichment (1 to 20 microM NO2- plus 100 microM NO3-), there was a pronounced nonlinear response in anammox activity. Maximal activity occurred between 2 and 5 microM NO2-, but the amplitude of this peak varied across the study (November 2003 to June 2004). Anammox accounted for as much as 82% of the NO2- added at 1 microM in November 2003 but only for 15% in May 2004 and for 26 and 5% of the NO2- added at 5 microM for these two months, respectively. Decreasing the concentration of NO3- but holding NO2- at 5 microM decreased the significance of anammox as a sink for NO2-. The behavior of anammox was explored by use of a simple anammox-denitrification model, and the concept of a biphasic system for anammox in estuarine sediments is proposed. Overall, anammox is likely to be regulated by the availability of NO3- and NO2- and the relative size or activity of the anammox population.
authors.affiliation: School of Biological Sciences, Queen Mary, University of London, London E1 4NS, United Kingdom. m.trimmer@qmul.ac.uk
authors.forename: Mark
authors.initials: M
authors.lastname: Trimmer
authors.forename: Joanna C
authors.initials: JC
authors.lastname: Nicholls
authors.forename: Nicholas
authors.initials: N
authors.lastname: Morley
authors.forename: Christian A
authors.initials: CA
authors.lastname: Davies
authors.forename: John
authors.initials: J
authors.lastname: Aldridge
mesh_terms: D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D008954:Models, Biological; D009565:Nitrate Reductases / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009572:Nitrite Reductases / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D045483:Rivers / Q000737:chemistry / Q000382:microbiology*
chemical_list: D009566:Nitrates; D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D009565:Nitrate Reductases; D009572:Nitrite Reductases