Interesting. Thanks for the links.
The article begins with a confirmation of what I had thought and then goes on to explain a very specific strain of bacteria.
The removal of nitrogen from wastewater by nitrifiers and denitrifiers was the most efficient method in wastewater treatment. Autotrophic nitrification and anoxic denitrification played important roles in this process. Nitrifiers convert ammonia to nitrite, followed by nitrate. Denitrifiers reduce nitrate to nitrite, finally to N2, in which NO and N2O were the main intermediate products
(Joo et al., 2005). Due to the totally differences in physiology and biochemistry, the nitrifiers and denitrifiers had some disadvantages in the process of nitrogen removal treatment of wastewater. Nitrifiers were sensitive to organic matter (Kulikowska et al., 2010). However, organic compounds were necessary to the denitrifiers. In addition, the growth of nitrifiers relied on oxygen that was toxic to denitrifiers (Lloyd et al., 1987).
The particular strain of aerobic denitrifying bacteria is one they call L7 in the article. It says it was found to produce nitrogen gas in an aerobic environment. Very cool discovery.
GC–MS results showed that N2O was produced on both nitrate (Fig. 2A) and nitrite (Fig. 2B) served as substrate, respectively. The results also indicated that strain L7 emit N2O when 15NH4Cl (HNM, Fig. 2C) and 15NH4Cl plus hydroxylamine (HNM plus hydroxylamine, Fig. 2D) as nitrification substrates. N2O isotopic abundance ratios (Fig. 3) showed that the labeled 15,14N2O, 15,15N2O did appear in the headspace gas of HNM sample, although the abundance of N2O from NH4Cl was far less than that of nitrate, nitrite and NH4Cl plus hydroxylamine (Fig. 2). These results suggested that strain L7 was a heterotrophic nitrification–aerobic denitrifier. It could not only aerobically denitrify nitrate or nitrite to form N2O, but also nitrify ammonia to form N2O, and the later was rarely reported in other strains.
It concludes that this is the first, "...bacterial strain to denitrify nitrite to N2 and denitrifying nitrite and nitrate to N2O in aerobic condition." and that L7, "...is a promising candidate in the extensive application of various pollution control system including municipal wastewater, aquaculture industry, etc."
To apply that to the product that started this thread it is possible that they have isolated L7 and bottled it in conditions under which it would survive but the substrate (not the same meaning as in our tanks) used to culture the bacteria was very specific. I'm not sure that the environment we would be dumping the stuff into would match what is required for it's survival, let alone proliferation.
Though I now know that at least one strain of bacteria will denitrify aerobically I still remain dubious of bacterial starter products and wonder if their very precise experiment would ever play out naturally in our tanks without continued intervention on the part of the aquarist.
Great find, I love articles like that!