title: Bacterium-based NO2- biosensor for environmental applications.
abstract: A sensitive NO2- biosensor that is based on bacterial reduction of NO2- to N2O and subsequent detection of the N2O by a built-in electrochemical N2O sensor was developed. Four different denitrifying organisms lacking NO3- reductase activity were assessed for use in the biosensor. The relevant physiological aspects examined included denitrifying characteristics, growth rate, NO2- tolerance, and temperature and salinity effects on the growth rate. Two organisms were successfully used in the biosensor. The preferred organism was Stenotrophomonas nitritireducens, which is an organism with a denitrifying pathway deficient in both NO3- and N2O reductases. Alternatively Alcaligenes faecalis could be used when acetylene was added to inhibit its N2O reductase. The macroscale biosensors constructed exhibited a linear NO2- response at concentrations up to 1 to 2 mM. The detection limit was around 1 microM NO2-, and the 90% response time was 0.5 to 3 min. The sensor signal was specific for NO2-, and interference was observed only with NH2OH, NO, N2O, and H2S. The sensor signal was affected by changes in temperature and salinity, and calibration had to be performed in a system with a temperature and an ionic strength comparable to those of the medium analyzed. A broad range of water bodies could be analyzed with the biosensor, including freshwater systems, marine systems, and oxic-anoxic wastewaters. The NO2- biosensor was successfully used for long-term online monitoring in wastewater. Microscale versions of the NO2- biosensor were constructed and used to measure NO2- profiles in marine sediment.
authors.affiliation: Department of Microbiology, University of Aarhus, Aarhus, Denmark. mnielsen@biology.au.dk
authors.forename: Michael
authors.initials: M
authors.lastname: Nielsen
authors.forename: Lars Hauer
authors.initials: LH
authors.lastname: Larsen
authors.forename: Mike S M
authors.initials: MS
authors.lastname: Jetten
authors.forename: Niels Peter
authors.initials: NP
authors.lastname: Revsbech
mesh_terms: D042481:Alcaligenes faecalis / Q000254:growth & development / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods*; D003470:Culture Media; D004784:Environmental Monitoring / Q000379:methods*; D009585:Nitrogen Dioxide / Q000378:metabolism*; D009609:Nitrous Oxide / Q000378:metabolism; D012722:Sewage / Q000382:microbiology; D020588:Stenotrophomonas / Q000254:growth & development / Q000378:metabolism; D013696:Temperature; D014865:Waste Disposal, Fluid; D014871:Water Microbiology
chemical_list: D003470:Culture Media; D012722:Sewage; D009609:Nitrous Oxide; D009585:Nitrogen Dioxide