The effect of hydroxylamine on the activity and aggregate structure of autotrophic nitrifying bioreactor cultures.
Addition of hydroxylamine (NH2OH) to autotrophic biomass in nitrifying bioreactors affected the activity, physical structure, and microbial ecology of nitrifying aggregates. When NH2OH is added to nitrifying cultures in 6-h batch experiments, the initial NH3-N uptake rates were physiologically accelerated by a factor of 1.4-13. NH2OH addition caused a 20-40% decrease in the median aggregate size, broadened the shape of the aggregate size distribution by up to 230%, and caused some of the microcolonies to appear slightly more dispersed. Longer term NH2OH addition in fed batch bioreactors decreased the median aggregate size, broadened the aggregate size distribution, and decreased NH3-N removal from >90% to values ranging between 75% and 17%. This altered performance is explained by quantitative fluorescence in situ hybridization (FISH) results that show inhibition of nitrifying populations, and by qPCR results showing that the copy numbers of amoA and nxrA genes gradually decreased by up to an order-of-magnitude. Longer term NH2OH addition damaged the active biomass. This research clarifies the effect of NH2OH on nitrification and demonstrates the need to incorporate NH2OH-related dynamics of the nitrifying biomass into mathematical models, accounting for both ecophysiological and structural responses.
Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA. wharper@pitt.edu
Willie F
WF
Harper
Akihiko
A
Terada
Franck
F
Poly
Xavier
X
Le Roux
Ken
K
Kristensen
Mustafa
M
Mazher
Barth F
BF
Smets
D000641:Ammonia / Q000378:metabolism; D052818:Autotrophic Processes / Q000187:drug effects*; D001419:Bacteria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D018929:Cell Culture Techniques; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D019811:Hydroxylamine / Q000378:metabolism / Q000494:pharmacology*; D017404:In Situ Hybridization, Fluorescence; D009572:Nitrite Reductases / Q000235:genetics / Q000378:metabolism; D009606:Nitrosomonas / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction
D019811:Hydroxylamine; D000641:Ammonia; D010088:Oxidoreductases; D009572:Nitrite Reductases; C045582:ammonia monooxygenase